Animal Index - Invertebrates

Cyanobacterial Image Gallery

2007-08-16T02:01:00.000-07:00

Cyanobacterial Image Gallery

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Disclaimer and Acknowledgements
The images in this gallery are uncopyrighted freeware and are provided for educational purposes. Please contact the webmaster before using any of these images in a published work. A policy for image usage has been established. Images from Cyanosite have appeared in many publications including textbooks, review articles, and news reports. The images also have been used for presentations and museum exhibits worldwide.

Many of these images were taken from field samples. The measurements are approximate and not reliable for taxonomic use. It is hoped that the images will provide field technicians with some help in recognizing the creatures in the samples they have collected. Many of these pictures illustrate certain characteristics that are important in the ongoing discussion of morphological determination of cyanobacteria. Beggiatoa and "Chloroflexus" are not cyanobacteria, but they are included here because they are found in the same habitats as cyanobacteria, and because they could be confused with cyanobacteria. If you disagree with the taxonomic designations given here please submit your comments for inclusion.

The Webspinner is very grateful to those that have provided images to Cyanosite. Submission of additional images is always welcome. A policy for image usage is also available.

Back to Cyanosite

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Video Images
The Great Escape - A cyanobacterium defending itself from a ciliate predator.
Spirulina on the Move - Spirulina gyrating in solution.

Woodruffia grazing on Phormidium - Four separate video clips demonstrating avoidance mechanisms.

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Still Images
A full image can be obtained by clicking on a thumbnail sketch
Anabaena affinis, 640X

Anabaena circinalis - Measurement unavailable. probably 400x

Anabaena doliolum

Anabaena flos-aquae enlarged 2500X

Anabaena "laxa" - ID for this complex is of course tenuous--see next entry. Measurement unavailable. probably 400x

Anabaena "laxa" - From the same sample as above, a few weeks later. Note that the akinete is now adjacent the heterocyst. It now keys out to Anabaena "cylindrica". 400x

Anabaena scheremetievi - 400x phase contrast

Anabaena scheremetievi - A slight hint of a sheath is visible. 400x

Anabaena scheremetievi - 400x

Anabaena sperica, 1600X

Anabaena spherica - 400x

Anabaena spiroides - The line is 20 microns. 200x

Anabaena torulosa - 400x

Anabaena torulosa - Is it Synecococcus? No, it is Anabaena torulosa akinetes. 400x

Anabaena variabilis

Anabaena sp. - (Unidentified) No speculations upon the species. 400x

Anabaena sp. - (Unidentified) No speculations upon the species. 400x

Anabaena sp. - (Unidentified) No speculations upon the species. 400x

Anabaena sp. - (Unusual and contorted) Akinetes are round, so it is probably not A. circinalis. Could be A. spiroides in an unusual state. 200x.

Anabaena sp. - (Unusual and contorted) The same specimen as above at 100x.

Anabaena sp. - Probably A. scheremetievi, but akinetes were absent. A hint of a sheath is barely visible. 400x

Anabaena sp. - Probably A. circinalis, but akinetes were absent. 1000x

Anabaena sp. - Possibly A. viguieri, but the akinetes are too broad. 400x.

Anabaena sp., from freshwater lake in Oregon, 100X

Anabaena sp., from freshwater lake in Oregon, 100X

Anabaena sp., from freshwater lake in Oregon, 200X

Anabaena sp., from freshwater lake in Oregon, 100X. Note the fabulous germinating akinetes.

Anabaena sp.

Anabaena sp.

Anabaena sp.

Anabaena sp.

Anabaena sp. with symbiont bacteria (possibly Zoogloea) around heterocysts

Anabaenopsis circularis - The central pair of heterocysts is clearly visible. 200x

Anabaenopsis circularis - A developing pair of heterocysts is visible in the center of the trichome. Note the bacteria attached to it. 400x (phase contrast)

Anabaenopsis circularis - Same as above without phase contrast. 400x

Anabaenopsis sp. bloom in Bedetti Lake, Santo Tome, Santa Fe, Argentina

Anabaenopsis sp. bloom in Bedetti Lake, Santo Tome, Santa Fe, Argentina

Anabaenopsis sp. bloom in Bedetti Lake, Santo Tome, Santa Fe, Argentina

Anacystis nidulans TEM of semi-thin section (200 nm). See protocol.

Anacystis nidulans TEM of semi-thin section (200 nm) See protocol.

Anacystis nidulans TEM of semi-thin section (300 nm) See protocol.

Anacystis nidulans TEM of semi-thin section (300 nm) See protocol.

Anacystis nidulans TEM of semi-thin section (500 nm) See protocol.

Anacystis nidulans TEM of semi-thin section (500 nm) See protocol.

Aphanizomenon flos-aquae - Akinetes and heterocyst clearly visible. Measurement unavailable. probably 400x

Aphanizomenon flos-aquae - Colony. Measurement unavailable. probably 100x

Aphanizomenon flos-aquae - Colony. Akinetes absent. 400x

Aphanizomenon flos-aquae strain 1401/5. Autofluorescence image.

Aphanizomenon flos-aquae strain 1401/5. Autofluorescence image.

Aphanizomenon flos-aquae strain 1401/5. Autofluorescence image.

Arthrospira jenneri - Cross-walls obscured by cytoplasmic granules (sorry). 400x

Beggiatoa alba - 400x

Beggiatoa alba - Cropped portion of image above at higher resolution.

Bloom in waters at the Hartebeespoort dam in South Africa

Bloom of Microcystis aeruginosa and Anabaena circinalis on the St. Johns River, FL

Bloom of Aphanizomenon flos aquae in a lake in Surrey, UK

Bloom

Bloom of Microcystis in Crescent Lake, FL

Bloom in Doctor's Lake

Bloom in Lake Ponchartrain, LA, an oligohaline estuary

Bloom of Microcystis aeruginosa and Anabaena circinalis contaminated by a boat on the St. Johns River, FL

Bloom in agricultural setting in Missouri

Bloom in agricultural setting in Missouri

Bloom in agricultural setting in Missouri

Bloom in agricultural setting in Missouri

Bloom in agricultural setting in Missouri

Borzia sp.

Calothrix sp. PCC 7103

Calothrix sp.

Calothrix sp. showing terminal heterocysts

Chloroflexus sp. - Unknown phytoplankton from a fish pond. Speculation: Chloroflexus. 400x

Chloroflexus sp. - Wider view higher resolution image of specimen above.

Chroococcus sp.

Collecting cyanobacteria from a large bloom

Cyanobacterial bloom

Cyanosarcina sp. from a pulp and paper waste-treatment system in Brazil

Cylindrospermopsis raciborskii - Heterocysts and akinetes visible. 400x

Cylindrospermopsis raciborskii - 400x phase contrast

Cylindrospermopsis raciborskii - Heterocyst visible. 400x

Cylindrospermopsis raciborskii - Akinetes (only) visible. 400x phase contrast

Cylindrospermopsis raciborskii - Heterocyst visible. 400x phase contrast

Cylindrospermum muscicola - 400x

Cylindrospermum muscicola - Surprise! It is not Pseudanabaena, but C. muscicola, without akinetes, but with a developing heterocyst. 400x phase contrast

Cylindrospermum sp. str. PCC 7417

Cylindrospermum sp.

Cylindrospermum sp., 1600X

Cylindrospermum sp., 1600X

Eubacterium - Unidentified bacterium pays Euglena a visit. 1000x

Fischerella sp. str. PCC 7414

Fischerella sp.

Geitlerinema sp. from a pulp and paper waste-treatment system in Idaho

Girvanella sp. in algae oncolites from the Lower Cambrian Mule Spring Limestone, Waucoba Spring, Death Valley National Park

Gloeobacter sp. str. PCC 8105

Gloeobacter sp.

Gloeocapsa sp. together with two algae

"Gloeotrichia" - Akinete and heterocyst clearly visible. Measurement unavailable. 400x

"Gloeotrichia" - Colony. Measurement unavailable. 100x

Leptolyngbya africana

Leptolyngbya foveolarum f maior

Leptolyngbya foveolarum

Leptolyngbya fragilis

Leptolyngbya sp.

Lyngbya aestuarii

Lyngbya majuscula

Lyngbya sp.

Lyngbya sp. showing classical sheath and terminal differentiation in the lower filament

Lyngbya sp. showing formation of a coil at the end of a "hairpin" formation

Lyngbya sp. - (Unidentified) No speculations upon the species. 200x

Lyngbya sp. - (Unidentified) No speculations upon the species. Note that one has no visible sheath. 200x

Lyngbya sp. - Same specimen as above. 400x phase contrast

Lyngbya sp. - (Unidentified) Possibly birgei. 200x

Lyngbya sp. - Social gathering of the above species. 200x

Lyngbya sp.

Lyngbya sp.

Lyngbya sp., two cells are leaving the shell

Lyngbya sp.

Lyngbya sp. at 100 X.

Mat Community Knit strings of cyanobacteria from green layer of a microbial mat from Great Sippewissett Saltmarsh, Falmouth, MA

Mat Community Cross-section of a microbial mat from Great Sippewissett Saltmarsh, Falmouth, MA

Merismopedia - Colony of Merismopedia (Agmenellum [Drouet], Synechocystis Low GC cluster [Waterbury and Rippka]). 200x

Merismopedia elegans, 640X

Microcoleus chthonoplastes

Microcoleus vaginatus

Microcoleus sp. - One of those in the anomalous Microcoleus/Symploca/Lyngbya/Take-a-guess range. 400x

Microcrust on soil

Microcystis aeruginosa enlarged 2500X

Microcystis aeruginosa strain PCC 7806. Autofluorescence image.

Microcystis aeruginosa strain PCC 7806. Autofluorescence image.

Microcystis aeruginosa strain PCC 7806. Autofluorescence image.

Microcystis aeruginosa strain PCC 7806. Autofluorescence image.

Microcystis aeruginosa strain PCC 7806. Autofluorescence image.

Microcystis aerogenosa strain 1450/10 in very old (6 month) stationary phase cultures imaged with autofluoresence. 1000X

Microcystis aerogenosa strain 7806 in very old stationary phase cultures imaged with autofluoresence. Note transient "bright strike" feature. 1000X

Microcystis aerogenosa strain 7806 in very old (100 d) stationary phase cultures imaged with phase contrast. Note multi-planar division. 1000X

Microcystis aerogenosa strain 7806 in very old (100 d) stationary phase cultures imaged with phase contrast. Note narrow sheath. 1000X

Microcystis aerogenosa. 100X

Microcystis sp. bloom

Microcystis sp. - Becoming confluent. 200x

Microcystis sp. bloom from bird's eye view

Microcystis aeruginosa bloom, Lake Mokoan, Victoria, Australia.

Microcystis sp.

Microcystis sp. - Separate colonies. 200x

Microcystis sp. bloom, Balgavies Loch, Dundee, Scotland, 1981.

Microcystis sp., bloom, Grandview Garden Park, Beijing

Mixture - Oscillatoria cf. chalybea, Planktothrix agardhii, and Anabaena spiroides. 200x

Mixture - Oscillatoria cf. chalybea, Planktothrix agardhii, and Arthrospira jenneri. 200x

Mixture, including Thiothrix and Oscillatoria sp.

Mixture, including Spirulina and Microcoleus sp. and diatoms together with Thiopediasp.

Mixture of cyanobacteria from microbial mat community

Mystery Bug - Truly strange. Spirulina major inside a bundle. 400x

Mystery Bug - Unidentified filament. Is it made of diatoms, desmids, cyanobacteria, or the unknown? 400x

Mystery Bug A - Planktothrix agardhii with a swollen terminal cell. 200x. For Mystery Bugs A through E, it has been suggested that the swollen terminal cells are fungal (chytrid) fruiting bodies (sporangia) as hyphae have been observed running the length of similar trichomes.

Mystery Bug B - Planktothrix agardhii with a double swollen terminal cell. 200x. See Mystery Bug A.

Mystery Bug C - Another odd Planktothrix agardhii. 400x phase contrast. See Mystery Bug A.

Mystery Bug D - Another odd Planktothrix agardhii. 400x phase contrast. See Mystery Bug A.

Mystery Bug E - Same as above without phase contrast. 400x. See Mystery Bug A.

Mystery wavy cyanobacteria

Mystery cyanobacteria in a colony

Mystery cyanobacteria showing vessicles

Mystery 13

Mystery 14

Mystery 15

Mystery 16

Nodularia spumigena enlarged 1250X

Nodularia sp. bloom in situ from an undersea porthole in the Baltic Proper

Nostoc (Anabaena) azollae - Heterocyst clearly visible. 400x

Nostoc (Anabaena) azollae - Numerous akinetes visible. 400x

Nostoc sp. - Possible germling. 400x

Nostoc sp. - Possible colony or is it a strange type of Anabaena spherica?. The only thing for sure is that nothing is for sure. 200x

Nostoc sp., 130X

Nostoc sp. at 10X

Nostoc sp.

Nostochopsis sp., cell and branching

Nostochopsis sp., gross structure

Nostochopsis sp., detailed image

Nostochopsis sp., pediellate heterocyst

Nostochopsis sp., intercalary heterocyst

Oscillatoria agardhii - Autofluorescence image.

Oscillatoria cf. chalybea - With Planktothrix agardhii, and possible Raphidiopsis sp. 200x

Oscillatoria "chlorina" - Quotes represent the contributor's resentment at identifying cyanobacteria using color. 400x

Oscillatoria geminata - 400x

Oscillatoria limnetica

Oscillatoria limosa, 640X

Oscillatoria margaritifera

Oscillatoria princeps - 200x

Oscillatoria princeps - 100x

Oscillatoria princeps - Social gathering with some friends. 200x

Oscillatoria splendida - 400x phase contrast

Oscillatoria subuliformis

Oscillatoria sp. - The famous "big Oscillatoria". Species not known. It may be undescribed. 200x

Oscillatoria sp. - Note the granules in the terminal cell, along with its thickened membrane. 400x

Oscillatoria sp. - With the bright light rendering its striking granules more visible. Note the spiral arrangement of the granules. 100x

Oscillatoria sp. - The same specimen as above. 200x

Oscillatoria sp. - At low magnification. 40x

Oscillatoria sp. together with a Synechocystis microcolony. Note the numerous bacteria in the background.

Oscillatoria sp.

Oscillatoria sp., 640X

Oscillatoria sp., likely a hormogonium, from a pulp and paper waste-treatment system in Brazil

Phormidium jenkelianum

Phormidium retzii - Tentative identification. 200x

Phormidium sp.

Phormidium sp.

Phormidium uncinatum - Tentative identification. 400x phase contrast

Phormidium uncinatum - Same as above without phase contrast. 200x

Phycobilisome diagram Each disk in the phycobilisome structure represents a hexameric aggregate, (alpha-beta)66, of a phycobiliprotein complexed with a linker protein: Phycoerythrin = red, Phycocyanin = blue, Allophycocyanin = light blue. The green elements are the two PSII reaction centers that associate with each phycobilisome.

Planktothrix (Oscillatoria) agardhii - With visible pseudovacuoles. 400x phase contrast

Planktothrix rubescens. 100x.

Pleurocapsa sp. str. PCC 7440

Raphidiopsis curvata - Mixed with some straight chains that are either more Raphidiopsis or Cylndrospermopsis raciborskii without akinetes or heterocysts. 400x

Raphidiopsis curvata - Same as above with phase contrast

Raphidiopsis cf. mediterranea - Could be R. brookii. 400x

Raphidiopsis cf. mediterranea - 100x

Raphidiopsis curvata - 200x

Raphidiopsis cf. mediterranea - Pseudovacuoles clearly visible. 400x phase contrast

Schizothrix lenormandiana

Scytonema cf. Crustaceum

Scytonema sp.

Spirulina major - 400x phase contrast

Spirulina sp.

Spirulina sp.

Spirulina sp.

Spirulina sp.

Spirulina sp.

Spirulina subsalsa

Spirulina sp. (Arthrospira) culture contaminated by brown swans in South Bend, IN.

Stromatolites

Stromatolites

Stromatolites

Stromatolites

Columnar Stromatolites and Thrombolites from tidal channel at Lee Stocking Island, Bahamas

Stromatolite Cross-section, columnar procaryotic stromatolite grown on Calianassa burrow. Bar = 1 cm.

Stromatolite Photomicrograph, thin section of prokaryotic stromatolite showing alternating layers of dense micrite and coarse detritus.

Stromatolite Photomicrograph, thin section of eukaryotic stromatolite showing undulose laminations formed by a combination of eukaryotic algal and cyanobacterial activities.

Stromatolites found in Middle Proterozoic formations of the Hakatai Shale in Grand Canyon National Park.

Stromatolites found in Middle Proterozoic formations of the Hakatai Shale in Grand Canyon National Park. Lens cap is 55 mm.

Stromatolites found in Middle Proterozoic formations of the Hakatai Shale in Grand Canyon National Park. Lens cap is 55 mm.

Stromatolites found in Middle Proterozoic formations of the Hakatai Shale in Grand Canyon National Park.

Stromatolite crossection

Frozen Stromatolites, Shark's Bay, Australia

Frozen Stromatolites, Shark's Bay, Australia

Frozen Stromatolite Mat, Shark's Bay, Australia

Frozen Stromatolite, Shark's Bay, Australia

Frozen Stromatolites, Shark's Bay, Australia

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Living Stromatolites, Salda Lake, Turkey

Stromatoids, dry lake bed near Agaean Sea

Stromatoids, dry lake bed near Agaean Sea

Stromatoids, dry lake bed near Agaean Sea

Synechocystis buzasii

Synechocystis sp.

Thrombolite Heads heavily overgrown by Lee Stocking Island, Bahamas

Thrombolite of modern origin from Lee Stocking Channel, Bahamas. Bar = 1 cm.

Thrombolite Photomicrograph, thin section showing boundary between micritic clot and detritus-rich sediment pocket

Tolypothrix sp. strain A

Tolypothrix sp. strain A

Trichodesmium sp., Nomarski optics, 1000x

Trichodesmium sp., Nomarski optics, 1000x

Trichodesmium sp., Phase contrast, 1000x

Trichodesmium sp., Fluorescence optics, 1000x

Trichodesmium sp., Fluorescence optics, 1000x

Trichodesmium sp., Phase contrast, 1000x

Trichormus sp.

A Webserver for Cyanobacterial Research

2007-08-16T02:00:00.000-07:00

Features Resources Announcements Submissions

A Webserver for Cyanobacterial Research

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Features
Cyanobacteria Image Gallery presenting over 200 beautiful images or videos of cyanobacteria. With thumbnails (longer download).
Or Without thumbnails (shorter download).

Cyanobacteria Bibliography CyBib v5 The most extensive cyanobacterial bibliography on-line. It contains nearly 25,000 references and can be imported into reference managing programs on any platform. Now searchable on-line.

Cyanobacteria Links Library to cyanobacterial sites on the WWW.

CyanoNews has been discontinued. A few back issues can be obtained here

The Toxic Cyanobacteria Homepage now resides on Cyanosite with information about cyanobacterial toxins.

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Resources
Media Recipes for Culturing Cyanobacteria

Experimental Protocols

CyanoBase at Kazusa DNA Research Institute provides the entire sequence of several cyanobacteria.

Taxonomy of Cyanobacteria

Directory of Cyanobacteriologist. This list is from 2001 and likely will not be updated.

Cyanobacteriologist Email Directory (with tables) and without tables (smaller file). This list is from 2001 and likely will not be updated.

Cyanosite Mailing List. This list is only for announcements about Cyanosite.

History of Cyanosite including the first on-line version of Cyanosite from 1995

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Announcements
Great website on toxic cyanobacterial blooms; loaded with practical information for the general public.

The International Society for Applied Phycology (ISAP) has been formed. You are invited to become a member of this new society. You can learn more here.

Cyanosite was awarded a two-year grant from the The Waksman Foundation for Microbiology to support an undergraduate stipend. The work-study student helped to maintain CyBib and weblinks while adding useful information to the site. We are most appreciative of this opportunity for substantial practical improvement of the site.

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Awards

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Submissions
Cyanosite is dedicated to information transfer within the cyanobacterial research community. This site will work to maintain archives of experimental protocols, taxonomic information, comprehensive bibliographic information, educational resources for college and secondary school teachers, general information about blue-green algae, and links to other cyanobacterial, prochlorophyte, and cyanelle sites on the web. What you can do to help Cyanosite grow.

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Questions and comments can be directed to: Dr. Mark A. Schneegurt, mark.schneegurt@wichita.edu

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Cyanosite receives support from the Department of Biological Sciences at Purdue University

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Introduction to the Cyanobacteria

2007-08-16T01:58:00.000-07:00

Introduction to the Cyanobacteria

Architects of earth's atmosphere

Cyanobacteria are aquatic and photosynthetic, that is, they live in the water, and can manufacture their own food. Because they are bacteria, they are quite small and usually unicellular, though they often grow in colonies large enough to see. They have the distinction of being the oldest known fossils, more than 3.5 billion years old, in fact! It may surprise you then to know that the cyanobacteria are still around; they are one of the largest and most important groups of bacteria on earth.

Many Proterozoic oil deposits are attributed to the activity of cyanobacteria. They are also important providers of nitrogen fertilizer in the cultivation of rice and beans. The cyanobacteria have also been tremendously important in shaping the course of evolution and ecological change throughout earth's history. The oxygen atmosphere that we depend on was generated by numerous cyanobacteria during the Archaean and Proterozoic Eras. Before that time, the atmosphere had a very different chemistry, unsuitable for life as we know it today.

The other great contribution of the cyanobacteria is the origin of plants. The chloroplast with which plants make food for themselves is actually a cyanobacterium living within the plant's cells. Sometime in the late Proterozoic, or in the early Cambrian, cyanobacteria began to take up residence within certain eukaryote cells, making food for the eukaryote host in return for a home. This event is known as endosymbiosis, and is also the origin of the eukaryotic mitochondrion.

Because they are photosynthetic and aquatic, cyanobacteria are often called "blue-green algae". This name is convenient for talking about organisms in the water that make their own food, but does not reflect any relationship between the cyanobacteria and other organisms called algae. Cyanobacteria are relatives of the bacteria, not eukaryotes, and it is only the chloroplast in eukaryotic algae to which the cyanobacteria are related.

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Click on the buttons below to find out more about the Cyanobacteria.

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Images of Nostoc and Oscillatoria provided by the University of Wisconsin Botanical Images Collection.

For more information about cyanobacteria on the web, visit Cyanosite, a webserver dedicated to cyanobacterial research.

Information about the ecology of fresh-water cyanobacteria is available from the Soil and Water Conservation Society of Metro Halifax.

The Tree of Life has a preliminary page on the Cyanobacteria, with some very nice pictures.

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Photosynthetic Pigments

2007-08-16T01:57:00.000-07:00

Photosynthetic Pigments

Pigments are colorful compounds.
Pigments are chemical compounds which reflect only certain wavelengths of visible light. This makes them appear "colorful". Flowers, corals, and even animal skin contain pigments which give them their colors. More important than their reflection of light is the ability of pigments to absorb certain wavelengths.

Because they interact with light to absorb only certain wavelengths, pigments are useful to plants and other autotrophs --organisms which make their own food using photosynthesis. In plants, algae, and cyanobacteria, pigments are the means by which the energy of sunlight is captured for photosynthesis. However, since each pigment reacts with only a narrow range of the spectrum, there is usually a need to produce several kinds of pigments, each of a different color, to capture more of the sun's energy.

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There are three basic classes of pigments.

Chlorophylls are greenish pigments which contain a porphyrin ring. This is a stable ring-shaped molecule around which electrons are free to migrate. Because the electrons move freely, the ring has the potential to gain or lose electrons easily, and thus the potential to provide energized electrons to other molecules. This is the fundamental process by which chlorophyll "captures" the energy of sunlight.
There are several kinds of chlorophyll, the most important being chlorophyll "a". This is the molecule which makes photosynthesis possible, by passing its energized electrons on to molecules which will manufacture sugars. All plants, algae, and cyanobacteria which photosynthesize contain chlorophyll "a". A second kind of chlorophyll is chlorophyll "b", which occurs only in "green algae" and in the plants. A third form of chlorophyll which is common is (not surprisingly) called chlorophyll "c", and is found only in the photosynthetic members of the Chromista as well as the dinoflagellates. The differences between the chlorophylls of these major groups was one of the first clues that they were not as closely related as previously thought.

Carotenoids are usually red, orange, or yellow pigments, and include the familiar compound carotene, which gives carrots their color. These compounds are composed of two small six-carbon rings connected by a "chain" of carbon atoms. As a result, they do not dissolve in water, and must be attached to membranes within the cell. Carotenoids cannot transfer sunlight energy directly to the photosynthetic pathway, but must pass their absorbed energy to chlorophyll. For this reason, they are called accessory pigments. One very visible accessory pigment is fucoxanthin the brown pigment which colors kelps and other brown algae as well as the diatoms.

Phycobilins are water-soluble pigments, and are therefore found in the cytoplasm, or in the stroma of the chloroplast. They occur only in Cyanobacteria and Rhodophyta.
The picture at the right shows the two classes of phycobilins which may be extracted from these "algae". The vial on the left contains the bluish pigment phycocyanin, which gives the Cyanobacteria their name. The vial on the right contains the reddish pigment phycoerythrin, which gives the red algae their common name.

Phycobilins are not only useful to the organisms which use them for soaking up light energy; they have also found use as research tools. Both pycocyanin and phycoerythrin fluoresce at a particular wavelength. That is, when they are exposed to strong light, they absorb the light energy, and release it by emitting light of a very narrow range of wavelengths. The light produced by this fluorescence is so distinctive and reliable, that phycobilins may be used as chemical "tags". The pigments are chemically bonded to antibodies, which are then put into a solution of cells. When the solution is sprayed as a stream of fine droplets past a laser and computer sensor, a machine can identify whether the cells in the droplets have been "tagged" by the antibodies. This has found extensive use in cancer research, for "tagging" tumor cells.

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Introduction to the Rhodophyta

2007-08-16T01:51:00.000-07:00

Introduction to the Rhodophyta
The red "algae"

Red algae are red because of the presence of the pigment phycoerythrin; this pigment reflects red light and absorbs blue light. Because blue light penetrates water to a greater depth than light of longer wavelengths, these pigments allow red algae to photosynthesize and live at somewhat greater depths than most other "algae". Some rhodophytes have very little phycoerythrin, and may appear green or bluish from the chlorophyll and other pigments present in them.

In Asia, rhodophytes are important sources of food, such as nori. The high vitamin and protein content of this food makes it attractive, as does the relative simplicity of cultivation, which began in Japan more than 300 years ago.

Some rhodophytes are also important in the formation of tropical reefs, an activity with which they have been involved for millions of years; in some Pacific atolls, red algae have contributed far more to reef structure than other organisms, even more than corals. These reef-building rhodophytes are called coralline algae, because they secrete a hard shell of carbonate around themselves, in much the same way that corals do.

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Click on the buttons below to learn more about the Rhodophyta.

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For more information:
Algae: The Forgotten Treasure of Tidepools is an excellent exhibit at Sonoma State on California tidepool algae, including red algae.

Visit Michael Rasser's pages on FOSSIL CORALLINE ALGAE (Corallinaceae: Rhodophyta).

For more on the biology and economic uses of seaweeds, including rhodophytes, visit the marine plants database of the DELTA Project, or the Seaweed Information Server maintained at University College Galway, Ireland. Or go to the exhibit on Porphyra, a typical red alga, from the Protist Image Database at the University of Montreal.

Derek Keats at the University of Western Cape, South Africa, has put extensive information about the nongeniculate coralline algae on-line. David Hills has a page on Pleistocene crustose coralline algae.

For a fuller listing of on-line phycological collections resources, try our Phycological Collection Catalogs Listings.

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The image of Porphyra is one of several images of Rhodophyta available from the excellent Virtual Foliage Page image collection of the University of Wisconsin-La Crosse. Image used with permission.
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Introduction to the Psilotales

2007-08-16T01:49:00.000-07:00

Introduction to the Psilotales
the whisk ferns

The Psilotales are the least complex of all terrestrial vascular plants, and were once believed to be remnants of an otherwise extinct Devonian flora. This is primarily because psilophytes are the only living vascular plants to lack both roots and leaves. Though they have been considered “primitive,” recent developmental and molecular evidence suggests that the group may actually be reduced from fern-like ancestors. There is not universal agreement on this, but we here treat them with the ferns for that reason. Despite the uncertainty of their relationships, psilophytes do structurally resemble certain early vascular plants, and are used as a model for understanding the ecology of these plants.

This is a small group with only two genera, Psilotum, shown above left, and Tmesipteris, above right, neither with many species. Both genera grow in tropical or subtropical regions, where they occur on rich soil or as epiphytes. Psilotum occurs in North America in the Caribbean, and along the Gulf and Atlantic Coasts to as far north as North Carolina, and has been reported from one locality in Arizona. It may also be found in tropical Asia and on Pacific islands. Tmesipteris grows in New Caledonia and nearby areas of the South Pacific, including Australia and New Zealand.

In addition to its natural distribution, Psilotum is also found as a common weed in greenhouses, and sometimes escapes cultivation in regions with mild climate. It occasionally becomes a nuisance, but is still very popular for its unusual growth form. In Japan, more than 100 unusual breeds have been produced, some of them highly prized by cultivators.

The Psilotales have no fossil record at all.

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Morphology and Life History of Psilotales
The psilophyte stem lacks roots; it is anchored instead by a horizontally creeping stem called a rhizome. The erect portion of the stem bears paired enations, outgrowths which look like miniature leaves, but unlike true leaves, the enations have no vascular tissue. These paired outgrowths lie immediately below the spore-producing synangia, which produce the spores. The synangia appear to be the product of three sporangia which became fused over the course of evolution, and are borne on the tip of a short lateral branch. This is another feature in which the psilophytes differ from other living vascular plants; all other such plants produce their sporangia on their leaves. You can click on the picture of the synangia of Psilotum at right, for a better look at these structures.

When the synangia mature, they open to release yellow to whitish spores, from which the gametophyte plants will later emerge, like the one shown at left. The gametophytes are very small, usually less than two millimeters long. They are subterranean and saprophytic, getting their nutrition by absorbing substances dissolved in the environment. This is often aided by the presence of fungi which grow into the tissues of the gametophyte and through the surrounding soil.

Eventually, the gametophyte reaches sexual maturity, producing both egg and sperm cells. The multiflagellate sperm swim to the egg cells, where they unite to begin the sporophyte generation. Psilophyte gametophytes may even self-fertilize to produce a sporophyte plant. The resulting sporophyte begins its life as a dependent on its parent gametophyte, as in other seedless plants. But unlike the “bryophytes,” the sporophyte eventually gains independence from its parent, and establishes itself in the environment.

The mature sporophyte of Psilotum will often grow to 30 cm tall, and may grow even taller. It has no true leaves, and instead the stem is green and photosynthetic, being covered with stomates to allow gas exchange. As the cross-section at right shows, the stem has a central core of vascular tissue (protostele) which is usually lobed. The thick-walled cells in the center of this core are sometimes considered to be pith, in which case the vascular arrangement would actually be a siphonostele. Surrounding the vascular tissue is a layer called the endodermis, which has specially packed cells to regulate flow of water and nutrients.

Tmesipteris has similar reproductive structures and life history to that of Psilotum, but by contrast it has broad leaf-like extensions of its stem, each with a single vascular bundle. These extensions may lie to either side of the stem, forming a flat growth, or they may be radially arranged. In any case, they are not considered leaves by most botanists, though this interpretation has been challenged by some workers.

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There is a nice collection of Psilotum images at the University of Wisconsin; the image of the Psilotum gametophyte on this page was made available through them.

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The Devonian

2007-08-16T01:48:00.000-07:00

The Devonian

417 to 354 Million Years Ago
The Rhynie Chert in Scotland is a Devonian age deposit containing fossils of both Zosterophyllophytes and Trimerophytes, the two major lines of vascular plants. This indicates that prior to the start of the Devonian, the first major radiations of the plants had already happened. The oldest known vascular plants in the Northern Hemisphere are Devonian.

The vegetation of the early Devonian consisted primarily of small plants, the tallest being only a meter tall. By the end of the Devonian, ferns, horsetails and seed plants had also appeared, producing the first trees and the first forests. Archaeopteris, shown below left, is one of these first trees.

Also during the Devonian, two major animal groups colonized the land. The first tetrapods, or land-living vertebrates, appeared during the Devonian, as did the first terrestrial arthropods, including wingless insects and the earliest arachnids. In the oceans, brachiopods flourished, like the beautifully pyritized brachiopod Paraspirifer bownockeri from Ohio, pictured above and to the right. Crinoids and other echinoderms, tabulate and rugose corals, and ammonites were also common. Many new kinds of fish appeared.

During the Devonian, there were three major continental masses: North America and Europe sat together near the equator, much of their current land underneath seas. To the north lay a portion of modern Siberia. A composite continent of South America, Africa, Antarctica, India, and Australia dominated the southern hemisphere.

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Click on the buttons below to learn more about the Devonian.

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Subdivisions of the
Devonian:
The chart at left shows the major subdivisions of the Devonian Period. This image is mapped to take you back to the Silurian, or forward in time to the Carboniferous Period.

The Devonian Period is part of the Paleozoic Era.

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One of the best places to learn more about the Devonian is the Devonian Times site.

Tour Devonian Fossil Gorge near Iowa City.

Visit Karl Wilson's site on New York Paleontology, which includes a nice section on New York in the Devonian.

Find out more about the Devonian paleontology and geology of North America at the Paleontology Portal.

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Introduction to the Pteridopsida

2007-08-16T01:47:00.000-07:00

Introduction to the Pteridopsida
the ferns

The ferns are an ancient lineage of plants, dating back to at least the Devonian. They include three living groups -- Marattiales, Ophioglossales, and leptosporangiate ferns -- as well as a couple of extinct groups. An additional group, the Psilotales, is tentatively included in the ferns, though the group is so vastly different from living ferns that no one is really certain of its relationships.

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Click on the buttons below to find out more about the Pteridopsida.

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For more about ferns, visit the American Fern Society. The AFS maintains a nice list of fern-related links.

For more information on fern relationships and fern biology, visit the Filicopsida page on the Tree of Life.

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Introduction to the Dinoflagellata

2007-08-16T01:46:00.001-07:00

Introduction to the Dinoflagellata

Dinoflagellates are unicellular protists which exhibit a great diversity of form. The largest, Noctiluca, may be as large as 2 mm in diameter! Though not large by human standards, these creatures often have a big impact on the environment around them. Many are photosynthetic, manufacturing their own food using the energy from sunlight, and providing a food source for other organisms. Some species are capable of producing their own light through bioluminescence, which also makes fireflies glow. There are some dinoflagellates which are parasites on fish or on other protists.

The most dramatic effect of dinoflagellates on life around them comes from the coastal marine species which "bloom" during the warm months of summer. These species reproduce in such great numbers that the water may appear golden or red, producing a "red tide". When this happens many kinds of marine life suffer, for the dinoflagellates produce a neurotoxin which affects muscle function in susceptible organisms. Humans may also be affected by eating fish or shellfish containing the toxins. The resulting diseases include ciguatera (from eating affected fish) and paralytic shellfish poisoning, or PSP (from eating affected shellfish, such as clams, mussels, and oysters); they can be serious but are not usually fatal.

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Click on the buttons below to find out more about the Dinoflagellata.

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For additional information:
For an excellent summary of modern dinoflagellates, click here for Andrew MacRae's Dinoflagellates page at the University of Calgary. You can also try the Protist Image Data Base for information about the dinoflagellate genus Peridinium. Or read Jeff Shield's page on Parasitic dinoflagellates of crustaceans.

For a fuller listing of on-line phycological collections resources, try our Phycological Collections Catalogs Listings.

You can get information about ciguatera fish poisoning and shellfish poisoning from the Food and Drug Administration's on-line handbook of foodborne pathogenic microbes and natural toxins.

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Sources:
Introduction to the Algae by H. C. Bold and M. J. Wynne, 1985 Prentice-Hall.
Handbook of Protoctista by L. Margulis et al., 1990 Jones and Bartlett, chapter on Dinoflagellata by F. J. R. Taylor

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Introduction to the Apicomplexa

2007-08-16T01:45:00.001-07:00

Introduction to the Apicomplexa

Parasitic, pathogenic protists
In traditional protist taxonomy, most parasitic protists were placed in the class Sporozoa. This group has since been found to include protists from a number of unrelated lineages, and has been dropped from current usage. However, many of the protists in the old Sporozoa share certain structural features, in particular an apical complex of microtubules within the cell. These protists have now been grouped in the Apicomplexa, probably the largest and best-known taxon of parasitic protists. There are about 4,000 known species, but this is almost certainly a gross underestimate of the actual number.

There are no known fossil apicomplexans. However, the group is a very important part of the living biota. Apicomplexans infect both invertebrates and vertebrates; they may be relatively benign or may cause serious illnesses. Species in the genus Plasmodium cause malaria in humans and other animals; an estimated 300 million people in over 90 countries are infected with malaria, and over 1 million die from it each year. Other apicomplexans cause serious illnesses, such as coccidiosis and toxoplasmosis, in humans and domestic animals. On the other hand, apicomplexans that infect insects have been used experimentally to control populations of insect pests.

Apicomplexans have complex life cycles, and there is much variation among different apicomplexan groups. Both asexual and sexual reproduction are involved, although some apicomplexans skip one or the other stage. The basic life cycle may be said to start when an infective stage, or sporozoite, enters a host cell, and then divides repeatedly to form numerous merozoites. Some of the merozoites transform into sexually reproductive cells, or gamonts. Gamonts join together in pairs and form a gamontocyst (pictured above). Within the gamontocyst, the gamonts divide to form numerous gametes. Pairs of gametes then fuse to form zygotes, which give rise by meiosis to new sporozoites, and the cycle begins again. Apicomplexans are transmitted to new hosts in various ways; some, like the malaria parasite, are transmitted by infected mosquitos, while others may be transmitted in the feces of an infected host, or when a predator eats infected prey.

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For additional information:
Biomedical information about Plasmodium and malaria is available from the Malaria Database maintained at Monash University, Australia. A good epidemiological overview of human malaria is presented by the World Health Organization.

Information on apicomplexans that infect domestic animals is available from Oklahoma State University College of Veterinary Medicine or from the Cryptosporidium Research lab at Kansas State University. General information on various pathogenic apicomplexans is available through MicroWeb.

Life stages of gregarine apicomplexans are portrayed in this 19th-century zoological chart preparted by the great zoologist and parasitologist Rudolph Leuckart.

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Source:
Levine, N. D. 1985. Phylum II. Apicomplexa. In: Lee, J.J., Hutner, S.H., and Bovee, E.C. (eds.) An Illustrated Guide to the Protozoa. Society of Protozoologists, Lawrence, Kansas.
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Introduction to the Ciliata

2007-08-16T01:44:00.000-07:00

Introduction to the Ciliata

The Ciliata, or Ciliophora, includes about 7000 known species of some of the most complex single-celled organisms ever. They derive their name from the Latin word for "eyelash," which describes the appearance of many ciliates quite well: some or all of the surface of a ciliate is covered with relatively short, dense hairlike structures, the cilia, which beat to propel the ciliate through the water and/or to draw in food particles.

Ciliates include some of the largest free-living protists; a few genera may reach two millimeters in length. They are abundant in almost every environment with liquid water: ocean waters, marine sediments, lakes, ponds, and rivers, and even soils. Because individual ciliate species vary greatly in their tolerance of pollution, the ciliates found in a body of water can be used to gauge the degree of pollution quickly.

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Click on the buttons below to learn more about the Ciliata.

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For more information, visit the Ciliate Homepage.

The electron micrograph of Paramecium on this page was provided by BIODIDAC.

The 19th-century zoologist Rudolph Leuckart created a classic series of wall charts, now available on-line from the Marine Biological Laboratory at Woods Hole, Massachusetts. Several of his images of ciliates are available; look under "Infusoria," an older name for the Ciliata.

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Introduction to the Foraminifera

2007-08-16T01:43:00.000-07:00

Introduction to the Foraminifera
Foraminifera (forams for short) are single-celled protists with shells. Their shells are also referred to as tests because in some forms the protoplasm covers the exterior of the shell. The shells are commonly divided into chambers which are added during growth, though the simplest forms are open tubes or hollow spheres. Depending on the species, the shell may be made of organic compounds, sand grains and other particles cemented together, or crystalline calcite.

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A typical foram : In the picture about, the dark brown structure is the test, or shell, inside which the foram lives. Radiating from the opening are fine hairlike reticulopodia, which the foram uses to find and capture food.
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Fully grown individuals range in size from about 100 micrometers to almost 20 centimeters long. A single individual may have one or many nuclei within its cell. The largest living species have a symbiotic relationship with algae, which they "farm" inside their shells. Other species eat foods ranging from dissolved organic molecules, bacteria, diatoms and other single celled phytoplankton, to small animals such as copepods. They move and catch their food with a network of thin extensions of the cytoplasm called reticulopodia, similar to the pseudopodia of an amoeba, although much more numerous and thinner.

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Click on the buttons below to learn more about Foraminifera.

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For more information about foraminifera :
Try the Gulf of St. Lawrence Database, including images and information on Late Quaternary microfossils.

Click here to see images of some type specimens from the UCMP microfossil collections.

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Introduction to the "Green Algae"

2007-08-16T01:42:00.000-07:00

Introduction to the "Green Algae"

The "green algae" is the most diverse group of algae, with more than 7000 species growing in a variety of habitats. The "green algae" is a paraphyletic group because it excludes the Plantae. Like the plants, the green algae contain two forms of chlorophyll, which they use to capture light energy to fuel the manufacture of sugars, but unlike plants they are primarily aquatic. Because they are aquatic and manufacture their own food, these organisms are called "algae," along with certain members of the Chromista, the Rhodophyta, and photosynthetic bacteria, even though they do not share a close relationship with any of these groups.

The above picture shows a dense growth of sea lettuce (Ulva), growing in a tide pool at the Berkeley Marina. This is a marine species of "green algae" often found attached to rocks, and exposed at low tide.

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Click on the buttons below to find out more about the "Green Algae".

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Visit Wisconsin for pictures of various green algae, or try the Protist Image Data Base for information about Chlamydomonas, Tetraselmis, Halosphaera, and Pyramimonas, which are all "green algae". Additional images of green algae are available from Tavole di Botanica sistematica.

Algae: The Forgotten Treasure of Tidepools is an exhibit at Sonoma State, with images and information on California tidepool algae, including green algae.

Duke Univeristy maintains the Chlamydomonas Genetics Center, which includes databases and educational material. A more general offering is the Seaweed Information Server at University College Galway.

For a fuller listing of on-line phycological collections resources, try our Phycological Collection Catalogs Listings.

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Introduction to the Chromista

2007-08-16T01:41:00.000-07:00

From microbes to giants. . .
It may seem hard to believe that microscopic diatoms, with their delicate silica skeletons only forty millionths of a meter long, can be related to the giant kelps, which may grow as long as fifty meters, or that either one is related to the downy mildew that nearly destroyed the French wine industry. But they are related -- placed together in the great kingdom-level taxon Chromista.

The name Chromista means "colored", and although some chromists, like mildews, are colorless, most are photosynthetic. Even though they are photosynthetic, chromists are not at all closely related to plants, or even to other algae. Unlike plants, the Chromista have chlorophyll c, and do not store their energy in the form of starch. Also, photosynthetic chromists often carry various pigments in addition to chlorophyll, which are not found in plants. It is these pigments which give them their characteristic brown or golden color.

Photosynthetic chromists are some of the most important organisms in aquatic ecosystems. The cool and temperate coasts of continents are lined with kelp forests, where many commercially important fish and shellfish feed and reproduce, and diatoms are frequently the primary source of food for both marine and fresh-water organisms.

In additional to their roles as producers for marine animals, chromists provide many products for industry. Alginates are viscous chemicals extracted from kelp; these are used in paper production, toothpaste, and in ice cream, where the alginate helps to improve texture and ensure uniform freezing and melting. Ancient chromists, like coccolithophorids, are responsible for deposits of limestone and other rock formations. The skeletons of dead chromists accumulate on the floor of lakes and oceans, where they may become thick deposits of silica or calcium carbonate. These deposits are useful for interpreting ancient climate, and in searching for oil.

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Click on the buttons below to learn more about the Chromista.

You can navigate deeper into the Chromista groups by selecting Systematics!

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Visit the Tree of Life for a current cladogram showing the relationships among the chromists, also known as stramenopiles.

More pictures of diatoms are available at the Algal Microscopy and Image Digitization server at Bowling Green State University.

For a fuller listing of on-line phycological collections resources, try our Phycological Collections Catalogs Listings.

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Images of kelp and Saprolegnia courtesy Wisconsin; coccolith image courtesy Dr. William Ruddiman and the US National Geophysical Data Center; picture of Odontella taken by Karen Wettmore.
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Introduction to the Testaceafilosea

2007-08-16T01:40:00.000-07:00

Introduction to the Testaceafilosea
the testate amoebae
There are a number of protists that are amoeboid; that is, they are more or less shapeless and move by means of extensions known as pseudopodia ("false feet"). This has been achieved many times in various eukaryote lineages; amoebas are a highly polyphyletic group. A number of amoebas are referred to as testate: they are partially enclosed in a shell, or test, that may be made of organic material, agglutinated particles, calcium carbonate, or silica. The testate amoebae probably make up a polyphyletic group, but one group of testate amoebae, the Testaceafilosea, is probably monophyletic, united by the synapomorphies of having long, thread-like pseudopodia and a test that is often made of silica plates.

The test of Trinema is shown here; Trinema is very common in the water films on mosses, in leaf litter, in moist soils, and on aquatic vegetation. (This specimen in particular was found on moss just outside of McCone Hall on the UC-Berkeley campus.) In life, the amoeboid cell would partialy fill the hollow test and extend pseudopodia from the aperture seen at the upper left.

Although these testate amoebae are non-photosynthetic and lack flagellated stages, their coating of siliceous scales is similar to that seen in some chromists. For this reason, some have placed the Testaceafilosea near the Chromista. A recent molecular study (Bhattacharya et al. 1995) rejects this position but suggests that these amoebae may actually be closely related to another algal group, the Chlorarachniophyta. Certainly more work will be required to pinpoint the relationships of these organisms.

The oldest filose testacean fossils may be late Precambrian, but because tests rapidly disintegrate into individual scales after the death of the amoeba, fossil Testaceafilosea are not well-known. However, tests of these and other amoebae may be common in Cenozoic and Quaternary lake deposits and peats, where they may provide information on paleoclimate and paleoecology.

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UCMP Research Report: "Bacteria and protozoa from middle Cretaceous amber of Ellsworth County, Kansas." Find out more about fossil testate amoebas from Cretaceous amber, a unique mode of preservation. Originally published in PaleoBios 17(1): 20-26.

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Source:
Bhattacharya, D., Helmchen, T., and Melkonian, M. 1995. Molecular evolutionary analyses of nuclear-encoded small subunit ribosomal RNA identify an independent rhizopod lineage containing the Euglyphina and the Chlorarachniophyta. Journal of Eukaryotic Microbiology 42(1): 65-75.
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Introduction to the Radiolaria

2007-08-16T01:39:00.000-07:00

Introduction to the Radiolaria
With their glassy skeletons of often perfect geometric form and symmetry, radiolarians are among the most beautiful of all protists. They are also an ancient group, going back all the way to the early Cambrian Period. Their abundance in many rocks, their long geologic history, and their diversity through time make them important sources of information on the geologic age and structure of many deposits.

Radiolaria can range anywhere from 30 microns to 2 mm in diameter. Their skeletons tend to have arm-like extensions that resemble spikes, which are used both to increase surface area for buoyancy and to capture prey. Most radiolarians are planktonic, and get around by coasting along ocean currents. Most are somewhat spherical, but there exist a wide variety of shapes, including cone-like and tetrahedral forms (see the image above). Besides their diversity of form, radiolarians also exhibit a wide variety of behaviors. They can reproduce sexually or asexually; they may be filter feders or predators; and may even participate in symbiotic relations with unicellular algae.

Though their silica skeletons have allowed us to find numerous fossils, scientists still have not been able to successfully develop a complete classification scheme for them. The evolution of the Radiolaria can be easily traced on the broad scale, with major transitions in the global fauna, but a concise taxomony reflecting the evolutionary relationships of major groups is still elusive. Until comparatively recently, radiolarians were primarily studied by micropaleontologists, and only at the end of the 20th century have scientists from other fields begun to study these fascinating protists as well.

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Click on the buttons below to learn more about the Radiolaria.

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Great Internet resources for radiolarians include:
A Guide to Modern Radiolaria
Radiolarian Database, Nagoya University
Radiolaria Home Page, Oregon State University
The Rad Page, by Fabrice Cordey

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Introduction to the Eukaryota

2007-08-16T01:38:00.000-07:00

Introduction to the Eukaryota
Fungi, Protists, Plants, Animals...

The Eukaryota include the organisms that most people are most familiar with - all animals, plants, fungi, and protists. They also include the vast majority of the organisms that paleontologists work with. Although they show unbelievable diversity in form, they share fundamental characteristics of cellular organization, biochemistry, and molecular biology. Shown here, clockwise from upper left: a dinoflagellate, a single-celled photosynthetic protist; a palm tree representing the plants; a spider, one of the animals; and a cluster of mushrooms representing the fungi.

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Click on the buttons below to learn more about the eukaryotes.

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Computer Model of the DNA Helix

2007-08-16T01:37:00.001-07:00

Computer Model of the DNA Helix
Despite what you may have seen in some textbooks, DNA is not built like a twisted ladder. The helix, or spiral, is an inherent feature of the DNA molecule. Notice, for instance, that in the picture below, that the groove on the left side of the picture is much larger than the right side. This is because the paired bases in the center meet each other at an angle.

DNA is a very large molecule; the image here shows only a tiny fraction of the typical molecule. If an entire molecule of DNA from the virus "bacteriophage lambda" were shown at this scale, the image would be 970 meters high. For the bacterium Escherichia coli, the image would be 80 kilometers long. And for a typical piece of DNA from a eukaryote cell, the image would stretch for 1600 kilometers, about as far as it is from Dallas to Washington, D. C.! Obviously such a large molecule is not fully stretched out inside the cell, but is wound around proteins called histones which protect the DNA.

You might also notice in the image that the two halves do not quite come in contact. In fact they are held together by hydrogen bonds, a sort of electrical attraction between partially negative atoms on the base of one side with the partially positive atoms on the other. Both sides have positive and negative charges. A single such pairing would not hold the molecule together well, but several million such bonds are quite effective. This also has the advantage that little effort is required to pull the two halves apart for replication, when the DNA is copied, and for transcription, when the DNA message is read. The message of DNA is the information from which the cell and its components are built.

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This model of DNA appears courtesy of the Image Library of Biological Macromolecules based in Jena, Germany, which maintains a large archive of spectacular computer graphics of DNA, RNA, and proteins. The background for this page was made by Jim Angus at the Los Angeles County Museum.
For more information about gene function, try The Natural History of Genes, which includes on-line activities.

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Introduction to the Viruses

2007-08-16T01:36:00.000-07:00

Introduction to the Viruses
In 1898, Friedrich Loeffler and Paul Frosch found evidence that the cause of foot-and-mouth disease in livestock was an infectious particle smaller than any bacteria. This was the first clue to the nature of viruses, genetic entities that lie somewhere in the grey area between living and non-living states.

Viruses depend on the host cells that they infect to reproduce. When found outside of host cells, viruses exist as a protein coat or capsid, sometimes enclosed within a membrane. The capsid encloses either DNA or RNA which codes for the virus elements. While in this form outside the cell, the virus is metabollically inert; examples of such forms are pictured below.

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Viral micrographs : To the left is an electron micrograph of a cluster of influenza viruses, each about 100 nanometers (billionths of a meter) long; both membrane and protein coat are visible. On the right is a micrograph of the virus that causes tobacco mosaic disease in tobacco plants.

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When it comes into contact with a host cell, a virus can insert its genetic material into its host, literally taking over the host's functions. An infected cell produces more viral protein and genetic material instead of its usual products. Some viruses may remain dormant inside host cells for long periods, causing no obvious change in their host cells (a stage known as the lysogenic phase). But when a dormant virus is stimulated, it enters the lytic phase: new viruses are formed, self-assemble, and burst out of the host cell, killing the cell and going on to infect other cells. The diagram below at right shows a virus that attacks bacteria, known as the lambda bacteriophage, which measures roughly 200 nanometers.

Viruses cause a number of diseases in eukaryotes. In humans, smallpox, the common cold, chickenpox, influenza, shingles, herpes, polio, rabies, Ebola, hanta fever, and AIDS are examples of viral diseases. Even some types of cancer -- though definitely not all -- have been linked to viruses.

Viruses themselves have no fossil record, but it is quite possible that they have left traces in the history of life. It has been hypothesized that viruses may be responsible for some of the extinctions seen in the fossil record (Emiliani, 1993). It was once thought by some that outbreaks of viral disease might have been responsible for mass extinctions, such as the extinction of the dinosaurs and other life forms. This theory is hard to test but seems unlikely, since a given virus can typically cause disease only in one species or in a group of related species. Even a hypothetical virus that could infect and kill all dinosaurs, 65 million years ago, could not have infected the ammonites or foraminifera that also went extinct at the same time.

On the other hand, because viruses can transfer genetic material between different species of host, they are extensively used in genetic engineering. Viruses also carry out natural "genetic engineering": a virus may incorporate some genetic material from its host as it is replicating, and transfer this genetic information to a new host, even to a host unrelated to the previous host. This is known as transduction, and in some cases it may serve as a means of evolutionary change -- although it is not clear how important an evolutionary mechanism transduction actually is.

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The image of influenza virus was provided by the Department of Veterinary Sciences of the Queen's University of Belfast. The tobacco mosaic virus picture was provided by the Rothamstead Experimental Station. Both servers have extensive archives of virus images.

The Institute for Molecular Virology of the University of Wisconsin has a lot of excellent information on viruses, including news, course notes, and some magnificent computer images and animations of viruses.

The Cells Alive! website includes information on the sizes of viral particles and an article on the mechanisms of HIV infection.

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Source: Emiliani, C. 1993. Extinction and viruses. BioSystems 31: 155-159.
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Introduction to the Metazoa

2007-08-16T01:35:00.000-07:00

Introduction to the Metazoa
Animals, Animals, Animals!

This collage of animals reveals just a tiny fraction of the fascinating world of zoology. Our exhibits on animals will help you make sense of the complex and beautiful story of their history. For each group of organisms (each taxon), we present information on the group's fossil record, life history, ecology, systematics and morphology. The Web pages on systematics (for instance . . .) show the various subgroups of each taxon, and are thus your connection to other exhibits in our UCMP Virtual Museum of Paleontology. If you do not want to follow phylogeny, you can always select our Web Lift to Taxa, at the bottom of most pages, to get to any of our exhibits on organisms.

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Click on the buttons below to learn more about Metazoa
Navigate deeper into the diverse animal groups by selecting Systematics!

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The Electronic Zoo offers links to all sorts of information on all sorts of animals.
For additional images of mostly invertebrate animals and protists, created in the 19th century by the great zoologist Rudolph Leuckart, click here to visit the Marine Biological Laboratory at Woods Hole, Massachusetts.

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Introduction to the Platyhelminthes

2007-08-16T01:34:00.000-07:00

Introduction to the Platyhelminthes
Life in two dimensions. . .
The simplest animals that are bilaterally symmetrical and triploblastic (composed of three fundamental cell layers) are the Platyhelminthes, the flatworms. Flatworms have no body cavity other than the gut (and the smallest free-living forms may even lack that!) and lack an anus; the same pharyngeal opening both takes in food and expels waste. Because of the lack of any other body cavity, in larger flatworms the gut is often very highly branched in order to transport food to all parts of the body. The lack of a cavity also constrains flatworms to be flat; they must respire by diffusion, and no cell can be too far from the outside, making a flattened shape necessary.

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Life without a coelom : The image at left is a fluke (possibly a species of Probolitrema). Flukes, like other parasitic flatworms, have complex life cycles often involving two or more host organisms. At right, a planarian (Dugesia). Planarians are free-living flatworms, and have a much simpler life history. They inhabit freshwater, and are carnivores (even without teeth) or scavengers. Most are less than a centimeter long. (Click on either of the pictures above for a larger image).

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Flatworms were once divided into three groups. The mostly free-living Turbellaria include the planarian, Dugesia, shown above; these are found in the oceans, in fresh water, and in moist terrestrial habitats, and a few are parasitic. The Trematoda, or flukes, are all parasitic, and have complex life cycles specialized for parasitism in animal tissues. Members of one major taxon of flukes, the Digenea -- which includes the human lung fluke depicted at right -- pass through a number of juvenile stages that are parasitic in one, two, or more intermediate hosts before reaching adulthood, at which time they parasitize a definitive host. The Cestoda, or tapeworms, are intestinal parasites in vertebrates, and they also show anatomical and life history modifications for parasitism.

It now seems likely that the first two of these groups are paraphyletic; that is, they contain some but not all descendants of a common ancestor. Recent molecular studies suggest that the Platyhelminthes as a whole may even be polyphyletic, having arisen as two independent groups from different ancestral groups. If this latter view is correct, then most of the flatworms may belong to the Lophotrochozoa, a large group within the animal kingdom that includes molluscs and earthworms, while the rest belong near the base of animal diversity.

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Marine flatworms : The marine flatworms (polycladids) are the largest of the free-living flatworms, sometimes reaching lengths of 15 centimeters. Polycladids get their name from their highly branched digestive cavity. These individuals were photographed on a reef near the island of Guam. (Click on either of the pictures above for a larger image).

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Platyhelminths have practically no fossil record. A few trace fossils have been reported that were probably made by platyhelminths (Alessandrello et al., 1988), and fossil trematode eggs have been found in Egyptian mummies and in the dried dung of Pleistocene ground sloth. Trematode larvae that parasitize molluscs may leave pits or thin spots on the inside of the shell, and these pits may be recognized on fossil shells. If the mollusc is irritated by the presence of trematode larvae, it may be able to surround them with layers of shelly material - and thus do parasites become natural pearls.

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Images of a number of free-living and parasitic flatworms, from Rudolph Leuckart's 19th century zoological wall charts, are available (look for "Platodes" in the index). More detailed classification of platyhelminths is available from the Tree of Life at the University of Arizona.

To find out more about tapeworms and flukes that cause human disease, read this handbook published by the U.S. Food and Drug Administration, view these pages produced by the World Health Organization. The disease schistosomiasis, or bilharzia, is a serious health problem in many parts of the world; you can learn more about it from the World Health Organization.

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Liver fluke photo provided by BIODIDAC, and used under conditions. Image of Dugesia taken by B. M. Waggoner & B. R. Speer. Images of polycladid marine flatworms taken by Allen G. Collins.
Sources:

Alessandrello, A., Pinna, G., and Teruzzi, G. 1988. Land planarian locomotion trail from the Lower Permian of Lombardian pre-Alps. Atti della Societa Italiana di Scienze Naturale e Storia Naturale, Milano, 129(2-3): 139-145.
R. Buchsbaum, M. Buchsbaum, J. Pearse, & V. Pearse, 1987. Animals Without Backbones. Chicago: University of Chicago Press.
Ruiz-Trillo, Iñaki, Marta Riutort, D. Timothy J. Littlewood, Elisabeth A. Herniou, & Jaume Baguñà, 1999. Acoel flatworms: Earliest extant bilaterian metazoans, not members of Platyhelminthes. Science 283: 1919-1923.
Winnepenninckx, B., T. Backeljau, L. Y. Mackey, J. M. Brooks, R. de Wachter, S. Kumar, & J. R. Garey. 1995. 18S rRNA data indicate that Aschelminthes are polyphyletic in origin and consist of at least three distinct clades. Molecular Biology & Evolution 12(6): 1132-1137.

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Introduction to the Lophotrochozoa

2007-08-16T01:31:00.000-07:00

Introduction to the Lophotrochozoa
Of molluscs, worms, and lophophores. . .
The Lophotrochozoa comprise one of the major groups within the animal kingdom, In turn, the Lophotrochozoa belongs to a larger group within the Animalia called the Bilateria, because they are bilaterally symmetrical with a left and a right side to their bodies.

The cladogram above shows the major groups in the Lophotrochozoa. Click on any box containing a picture to learn about that particular group. The phylogeny above is based on a combination of morphology and 18S RNA. It is not the final word on the relationships between these groups, and there are many competing hypotheses. For now, we prefer this grouping based on the available evidence, but as data continues to accumulate our picture of the relationships may change.

The name Lophotrochozoa comes from the names of the two major animal groups included: the Lophophorata and the Trochozoa. In the cladogram above, you can see this division. Those animals to the left side of the cladogram are the Lophophorata, while the groups along the top and right side (Nemertini through Annelida) belong to the Trochozoa.

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Trochozoa: These animals are all protostomes -- the mouth develops before the anus in the young embryo -- and they have long been recognized as belonging together as a group. Many of the members are worm-like, though not all of them are familiar or common. The two largest groups of trochozoans are the Mollusca (molluscs) and the Annelida (segmented worms).

It might seem strange at first to group earthworms and squid together. They certainly don't look much alike, but that is only true when looking at the adult form; there is a fundamental feature of their life history that they share. Many annelids and molluscs share patterns of development in early embryonic stages. When these larvae hatch, each is a microscopic swimmer known as a trochophore larva, shown at right. The larva has two bands of cilia around the middle that are used for swimming and for gathering food, and at the "top" is a cluster of longer flagellae. So the larvae of these groups is nearly identical, even though they mature into very different adult forms. Until very recently, the Arthropoda (insects & crustaceans) were considered possible close relatives of the Annelida, based on the fact that both groups are segmented, but no arthropod has a trochophore larva and no molecular studies support a close relationship.

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Lophophorata: This group includes the Phoronida and Entoprocta (both small groups) as well as the Bryozoa ("moss" animals) and Brachiopoda (brachiopods), both of which have an extensive fossil record. The feature shared by this group is the lophophore, an unusual feeding appendage bearing hollow tentacles.

While the Lophophorata are a well-recognized group, phylogenetic studies do not yet agree on the identity of their closest relatives. These animals were once included in the Pseudocoelomata, because they do not have a distinct internal body cavity like the Trochozoa, but this grouping does not hold together in modern studies. We have placed the Lophophorata in the Lophotrochozoa as the most popular of the current choices in the literature, but there are studies that suggest they may belong with the deuterostomes, or may even be paraphyletic.

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Trochophore larva diagram acquired through BIODIDAC, and used according to conditions.
Sources:

Eernisse, Douglas J., James S. Albert, & Frank E. Anderson, 1992. Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralean metazoan morphology. Systematic Biology 41(3):305-330.
Garey, James R. & Andreas Schmidt-Rhaesa, 1998. The essential role of "minor" phyla in molecular studies of animal evolution. American Zoology 38(6): 907-917.
Halanych, K. M., J. D. Bacheller, A. M. A. Aguinaldo, S. M. Liva, D. M. Hillis, & J. A. Lake. 1995. Evidence from 18S ribosomal DNA that the lophophorates are protostome animals. Science 267: 1641-1643.
Ruiz-Trillo, Iñaki, Marta Riutort, D. Timothy J. Littlewood, Elisabeth A. Herniou, & Jaume Baguñà, 1999. Acoel flatworms: Earliest extant bilaterian metazoans, not members of Platyhelminthes. Science 283: 1919-1923.
Valentine, James W., David Jablonski, & Douglas H. Erwin, 1999. Fossils, molecules and embryos: New perspectives on the Cambrian explosion. Development 126(5): 851-859.
Wallace, Robert Lee, Claudia Ricci, & Giulio Melone, 1996. A cladistic analysis of pseudocoelomate (aschelminth) morphology. Invertebrate Biology 115(2): 104-112.
Winnepenninckx, Birgitta, Thierry Backeljau, & Rupert de Wachter. 1995. Phylogeny of protostome worms derived from 18S rRNA sequences. Molecular Biology & Evolution 12(6): 641-649.
Winnepenninckx, B., T. Backeljau, L. Y. Mackey, J. M. Brooks, R. de Wachter, S. Kumar, & J. R. Garey. 1995. 18S rRNA data indicate that Aschelminthes are polyphyletic in origin and consist of at least three distinct clades. Molecular Biology & Evolution 12(6): 1132-1137.
Zrzavy, Jan, Stanislav Mihulka, Pavel Kepka, Ales Bezdek, & David Tietz, 1998. Phylogeny of the Metazoa based on morphological and 18S ribosomal DNA evidence. Cladistics 14(3): 249-285.

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Introduction to the Polychaeta

2007-08-16T01:30:00.000-07:00

Introduction to the Polychaeta
the bristleworms

Of the approximately 9000 species of annelids, more than 8000 are polychaetes. These segmented worms are among the most common marine organisms, and can be found living in the depths of the ocean, floating free near the surface, or burrowing in the mud and sand of the beach. Some, such as Eunice gigantea, may reach three meters long.

Polychaetes are known by many names: lugworms, clam worms, bristleworms, fire worms, palolo worms, sea mice, featherduster worms, etc., but all possess an array of bristles on their many leg-like parapodia -- the name polychaete, in fact, means "many bristles". The many common names reflect the wide array of body forms found in this group, unlike the earthworms and leeches which all have the same general appearance.

The delicate beauty of many polychaetes make them a favored subject for photography, and several are named after nymphs and goddesses of Greek myth, such as Nereis (the common "clam worm") and Aphrodite (the "sea mouse").

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Click on the buttons below to learn more about Polychaetes.

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Chaetozone is a newsletter dedicated to polychaete annelids; it is distributed electronically through the Biodiversity and Biological Collections Web Server at Cornell University.

The Wormlab Home Page has several excellent pictures of polychaetes, and a list of additional sites

You might also look at Chapter 9: Annelida of the Keys to the Invertebrates of Woods Hole for more information about the structure and kinds of polychaetes.

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Source:
Buchsbaum, R. 1987. Animals Without Backbones, 3rd ed. Univ. of Chicago Press, Chicago.

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Introduction to the Echiura

2007-08-16T01:29:00.000-07:00

Introduction to the Echiura

Spoon Worms and Innkeepers

Echiurans were included in the Annelida until recently, and they are still considered close relatives of the annelids. The body of an echiuran lacks annelid-type segmentation, but the distinctive free-swimming trochophore larval stages of echiurans and polychaetes are very similar. Both echiurans and annelids are classified together within a larger group, the Trochozoa. Echiurans have an extensible proboscis and a set of small hooks at the posterior end; hence the Latin name of the phylum, "spine-tails." In English, echiurans are referred to as "spoon worms" (when referred to at all).
Although there are only about 150 species of echiurans known today, they are quite common in some marine environments. Urechis caupo, the "innkeeper worm" pictured here, is common in some mudflats of the Pacific coast of California. Normally it inhabits a U-shaped burrow; it is shown here in a glass tube, in a laboratory experiment on feeding. The mucus net which it creates with its proboscis is just visible; the worm filters water through its burrow and traps planktonic organisms in this net. This is an unusual mode of feeding for echiurans, and most use their proboscises to move sedimentary detritus to their mouths. Urechis is known as the "innkeeper worm" because a number of marine organisms, including small crabs, polychaete worms, and fish, live as commensals inside the echiuran's burrow.

U-shaped burrows are known in the fossil record from Cambrian times. Some of these trace fossils may have been made by echiurans, but a number of other organisms make very similar burrows. Body fossils of echiurans are much rarer, since echiurans have no hard parts. The oldest plausible echiuran fossil is Pennsylvanian.

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For more information, visit V. Murina's page on the biology of Echiura, including a lengthy checklist of species.

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This photograph appears courtesy of Jeff Judd, a man who knows his mud. Here's a little more information from his Master's research on Urechis caupo.
Rudolph Leuckart, the great 19th century zoologist, created a classic set of wall charts in zoology. Click here for his illustration of echiurans and sipunculans (another phylum, probably related to the annelids).

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Introduction to the Pogonophora

2007-08-16T01:27:00.002-07:00

Introduction to the Pogonophora

Weird tube worms of the deepest seas

In 1900, a strange tube-dwelling worm was dredged from deep waters around Indonesia. While somewhat resembling tube-dwelling annelids, it lacked obvious segmentation; even more strangely, it also lacked a mouth, gut, or anus. This was the first discovery of the Pogonophora, an animal phylum restricted to the deep sea and remarkably common in certain habitats there.
About 80 pogonophoran species are known today, with new species still being discovered. One of the most spectacular zoological discoveries of recent years was the finding in 1977 of giant pogonophoran worms, 1.5 meters long, growing in heated, sulfur-rich water around warm-water vents in the Pacific Ocean, 2600 meters below the surface (pictured at right). These worms are sometimes placed in their own phylum, the Vestimentifera, but they are similar to pogonophorans in most respects, and the current tendency is to group these rift-dwelling worms together with the rest of the Pogonophora into one phylum.

The name Pogonophora is Greek for "beard-bearers," and comes from the fact that many species have from one to many tentacles at the anterior end. These tentacles somewhat resemble the lophophore found in animals like brachiopods and bryozoans, as well as the feeding tentacles of certain chordates. The incompletely known anatomy of pogonophorans was interpreted to show that pogonophorans were chordate relatives. Because pogonophorans live with their lower ends buried in mud, and were broken during the dredging process, it was not until 1964 that a complete pogonophoran was recovered. It turned out that pogonophorans have a segmented posterior end of the body -- the opisthosoma -- that bears setae and resembles an annelid body. The forward part of the body, or prosoma, is unsegmented. Because of the segmented opisthosoma, and because pogonophoran larvae have been found to look very much like annelid larvae, pogonophorans are now considered to be close relatives of the annelids, and are classified with them in a larger group, the Trochozoa.

How do pogonophorans feed with no mouth or gut? Some nutrition is provided by absorbing nutrients directly from the water with the tentacles. But most of a pogonophoran's nutrition is provided by symbiotic bacteria living inside the worm, in a specialized organ known as the trophosome that develops from the embryonic gut. Inside the trophosome, these bacteria oxidize sulfur-containing compounds such as hydrogen sulfide, which pogonophorans absorb through their tentacles -- the bright red color of rift-dwelling pogonophoran tentacles is due to hemoglobin, which absorbs both sulfides and oxygen for the use of the bacteria. The bacteria derive energy from sulfur oxidation, which they use to fix carbon into larger organic molecules, on which the pogonophoran feeds.

The fossil record of pogonophorans may extend back to the Vendian Period; long thin tubes known as sabelliditids have been found in rocks of that age, and somewhat resemble pogonophoran tubes. However, studies on sabelliditid structure have proved inconclusive in determining exactly what these fossils were. A few fossil pogonophoran-like tubes have turned up in later deposits (e.g. Adegoke 1967), but pogonophorans are generally quite rare as fossils.

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Visit this Dutch site on the Five Kingdoms for more info on the Pogonophora.

Keep in touch with the Tree of Life for information about the phylogeny and classification of pogonophorans.

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Our thanks go to Dr. Alyssa Arp, of San Francisco State University, who generously provided us with these images.
Sources:
Adegoke, O.S. 1967. A probable pogonophoran from the early Oligocene of Oregon. Journal of Paleontology 41(5): 1090-1094.

Ruppert, E.E. and Barnes, R.D. 1994. Invertebrate Zoology. 6th edition. Saunders College Publishing, Fort Worth.

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Annelida: More on Morphology

2007-08-16T01:27:00.001-07:00

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Annelida: More on Morphology
Annelids are coelomate animals; they have a fluid-filled body cavity in which the gut and other organs are suspended. Oligochaetes and polychaetes typically have spacious coeloms; in leeches, the coelom is reduced to a system of narrow canals, and archiannelids may lose the coelom entirely. The coelom is divided into separate compartments by partitions called septa, which give the "segmented worms" their segmented appearance.

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Annelida: Systematics

2007-08-16T01:26:00.001-07:00

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Annelida: Systematics

Annelids with a clitellum (a swelling towards the head of the animal, where the gonads are located) are classified in the Clitellata, which is further divided into Hirudinea (leeches) and Oligochaeta (including the earthworms). The Polychaeta lack a clitellum and have parapodia, paddle-like appendages with numerous bristles or chaetae. One aberrant group, the Myzostomaria, parasitizes echinoderms and is sometimes considered a separate class of annelids.

The "Archiannelida" consists of microscopic annelids that have reduced or lost many annelid features, such as chaetae, segments, and even the coelom. They are a still a poorly known group; some of them may be close to the ancestors of all annelids, but others are probably secondarily derived from polychaete ancestors. Hence they may not form a monophyletic clade, and are grouped here largely for the sake of convenience. Most are members of the meiofauna, the assemblage of microscopic animals and protists found living among sediment grains. They have no fossil record.

Two phyla that are probably close relatives of the Annelida, the Pogonophora (beardworms) and Echiura (spoon worms) are very rare as fossils, but all three groups belong to the larger group Trochozoa.

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Source: Willmer, P. 1990. Invertebrate Relationships: Patterns in Animal Evolution. Cambridge University Press, Cambridge.
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For more information on systematics of living annelids, try the pages on the Tree of Life project.
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Annelida: Life History and Ecology

2007-08-16T01:25:00.000-07:00

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Annelida: Life History and Ecology

Annelids have radiated into a number of niches. Some are parasitic, notably the leeches and myzostomarians; others filter-feed or prey on other invertebrates. However, probably the most significant ecological role played by annelids is reworking of soil and sediments. Many polychaetes and oligochaetes, and even a few leeches, are burrowers that constantly rework the sediment through which they burrow; in addition, they may ingest and excrete large quantities of sediments or soils. Robison (1987) notes that some sandy beaches may harbor 32,000 burrowing annelids per square meter, which collectively may ingest and excrete 3 metric tons of sand per year. The tubes sticking up from the sand in this picture, taken on a beach at Bahia de las Animas, Baja California, give some idea of how common polychaetes can be in such environments.

Soils may harbor 50 to 500 earthworms per square meter; they keep soils aerated, and their castings fertilize the soil.

Most earthworms and leeches are hermaphroditic with both male and female gonads. Polychaetes usually have separate sexes; many polychaetes hatch into a particular type of planktonic larva, the trochophore, which later metamorphoses into a juvenile annelid. Some polychaetes, however, can reproduce asexually, by budding.

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Source: Robison, R.A. 1987. Phylum Annelida. pp. 194-204. IN: Boardman, R.S., Cheetham, A.H., and Rowell, A.J. (eds.) Fossil Invertebrates. Blackwell Scientific, Palo Alto.
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Annelida: Fossil Record

2007-08-16T01:24:00.000-07:00

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Annelida: Fossil Record

Annelids probably originated in the Precambrian. Indeed, a few Vendian fossils, such as Spriggina, were once assigned to the Annelida; however, this identification is now doubted. Definite annelids appeared in the Cambrian. Pictured above is Canadia, from the Middle Cambrian Burgess Shale of British Columbia.

Canadia and other Cambrian polychaetes had no jaws, but some later polychaetes developed hard jaws, which are sometimes mineralized with iron oxide. Such polychaete jaws are fairly common in the fossil record, and are known as scolecodonts.

Body fossils of polychaetes are rarer, being generally restricted to Lagerstatten - localities with unusually good preservation of fossils. Mazon Creek, near downtown Chicago, is one of these localities where polychaetes have been found. Fossil oligochaetes are much rarer, and there are almost no fossil hirudineans (leeches) known.

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Introduction to the Annelida

2007-08-16T01:23:00.000-07:00

Introduction to the Annelida
Everybody's favorite, worms. . .

Segmented worms make up the Phylum Annelida. The phylum includes earthworms and their relatives, leeches, and a large number of mostly marine worms known as polychaetes. Various species of polychaete are known as lugworms, clam worms, bristleworms, fire worms, sea mice, and "EWWW! I stepped on that THING!"

Annelids can be told by their segmented bodies. Polychaetes (meaning "many bristles") have, predictably, many bristles on the body, while earthworms and leeches have fewer bristles. There are about 9000 species of annelid known today.

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Click on the buttons below to learn more about the Annelida.

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An Annelid Worm Biodiversity List is available, with links to a large number of annelid-related resources of all sorts. It also includes subscription information on the ANNELIDA e-mailing list.
Serious annelid connoisseurs should not miss the Biodiversity and Biological Collections Web Server. Those interested in vermiculture might prefer The Burrow, a remarkably designed Website with abundant information on earthworm farming. And not to forget the third main class of annelids, Mark Siddal's Hirudinea pages present original work on the evolution of leeches.

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Annelids: Worms and Leeches

2007-08-16T01:21:00.001-07:00

Annelids: Worms and Leeches
Annelids have bodies that are divided into segments. Annelids have very well-developed internal organs.

Some may have long bristles. Others have shorter bristles and seem smooth, like the earthworm shown here.

There are about 9,000 species of Annelids known today, including worms and leeches.

See Also:
Invertebrate Animals

Vertebrate Animals

The Animal Kingdom

Web Links

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Science Main Index

Web Sites about Annelids (worms):
Worm World

Museum of Paleontology at UC Berkeley

University of Michigan Animal Diversity Web

Copyright © 1998-2004 Kidport

Protozoa

2007-08-16T01:20:00.000-07:00

Protozoa
Protozoa are simple, single-celled animals. Most protozoa are microscopic in size.

There are several types of protozoa. The amoebas are clear, shapeless cells. Flagellates have a body shape looking like a hair.

Web Links:
"Protozoa" from the Department of Environmental and Evolutionary Biology at the University of Glasgow
See Also:
Invertebrate Animals

Vertebrate Animals

The Animal Kingdom

Web Links

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Science Main Index

Copyright © 1998-2004 Kidport

Animal Index - Invertebrates

2007-08-16T01:19:00.000-07:00

Animal Index - Invertebrates
Of the million or more animal species in the world, more than 98% are invertebrates. Invertebrates don't have an internal skeleton made of bone. Many invertebrates have a fluid-filled, hydrostatic skeleton, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans. There are many types of invertebrates. The most common invertebrates include the protozoa, annelids, echinoderms, mollusks and arthropods. Arthropods include insects, crustaceans and arachnids.

Click on the picture or name of the animals below for more information.
About Animals:
Index of Animals

Vertebrate Animals

Web Links

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Science Main Index

Protozoa Annelids Mollusks Echinoderms

Crustaceans Arachnids Insects
Web Links about Invertebrates:
Ask the Curator of Harvard's Museum of Comparative Zoology, Department of Invertebrate Zoology, your question.

Find information about the Invertebrates at the Waikiki Aquarium

Copyright © 1998-2004 Kidport