Difference between revisions of "Gastrotricha" - New World Encyclopedia
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==Description== | ==Description== | ||
− | '''Gastrotrichs''' (from [[Greek language|Greek]] ''gaster'' "stomach" and ''thrix'' "hair") are microscopic in size, ranging from 0.06 millimeters to 3 or 4 millimeters in length (Todaro 2006; Ramel 2008). | + | '''Gastrotrichs''' (from [[Greek language|Greek]] ''gaster'' "stomach" and ''thrix'' "hair") are microscopic in size, ranging from 0.06 millimeters to 3 or 4 millimeters in length (Todaro 2006; Ramel 2008). Their body is veriform (worm-like in appearance), with [[symmetry (biology)#Bilateral symmetry|bilaterally symmetry]] and a complete [[gut]]. The body is covered with [[cilia]], especially about the mouth and on the ventral surface. There are terminal projections with cement glands that serve in adhesion. This is a double-gland system where one gland secretes the glue and another secretes a de-adhesive to sever the connection. They do not have a circulatory system, but do have a nervous system with ganglia (Ramel 2008). Like many microscopic animals, their locomotion is primarily powered by hydrostatics. |
+ | Gastrotrichs are acoelomate—that is, they have no true [[coelom]] (body cavity). Originally they were thought to have a [[body cavity]] (pseudocoel), but this was an artifact created by preservation methods, and they are now known to be acoelomate. | ||
− | + | Gastrotrichs demonstrate [[eutely]], with a fixed number of [[cell (biology) cells]] within a species. That is, development proceeds to a particular number of cells, and further growth comes only from an increase in cell size. | |
− | + | ===Habitat== | |
+ | All species of Gastrotricha live in aquatic environments, both freshwater and saline ecosystems. Most fresh water species are part of the [[periphyton]] (mixture of algae, cyanobacteria, heterotrophic microbes, and [[detritus]] that is attached to submerged surfaces) and [[benthos]] (organisms which live on or in the bottom of water bodies), with presence to a lesser extent in the [[plankton]] (organisms that drift in bodies of water) (Todaro 2006). Marine species are found mostly interstitially in between sediment particles. | ||
− | + | There can be very high concentrations of gastrotrichs in aquatic [[ecosystem]]s. In freshwater, the population density may attain 158 individuals per ten square centimeters, ranking this [[taxon]] among the five most abundant taxa (Todaro 2006). In marine sediments, the density of gastrotrichs may reach 364 individuals per ten square centimeters, placing them third in abundance after the nematodes (Nematoda) and the harpacticoid copepods (Harpacticoida) (Todaro 2006). | |
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+ | and they reproduce entirely by [[parthenogenesis]]. Their relationship to other phyla is unclear. Morphology suggests that they are close to the [[Gnathostomulid]]a, the [[Rotifer]]a, or the [[Nematode|Nematoda]]. On the other hand genetic studies place them as close relatives of the [[flatworm|Platyhelminthes]], the [[Ecdysozoa]] or the [[Lophotrochozoa]]. About 700 species have been described. The average life span of a gastrotrich is very short - about three days. | ||
==Classification== | ==Classification== |
Revision as of 23:36, 5 June 2008
Gastrotrichs | ||||||||||
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Darkfield photograph of a gastrotrich.
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Scientific classification | ||||||||||
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Gastrotricha is a phylum of microscopic, free-living, aquatic worms, characterized by bilateral symmetry and an acoelomate body plan. These animals, which are mostly less than 3 millimeters in length, are found in both freshwater and marine ecosystems. They often have very high population densities. In marine sediments, they rank third in abundance and in freshwater ecosystems (as part of periphyton, benthos, and plankton), they rank among the top five most abundant groups (Todaro 2006). There are about 750 species, arranged into two orders, Chaetonotida and Macrodasyida (Todaro 2006).
Description
Gastrotrichs (from Greek gaster "stomach" and thrix "hair") are microscopic in size, ranging from 0.06 millimeters to 3 or 4 millimeters in length (Todaro 2006; Ramel 2008). Their body is veriform (worm-like in appearance), with bilaterally symmetry and a complete gut. The body is covered with cilia, especially about the mouth and on the ventral surface. There are terminal projections with cement glands that serve in adhesion. This is a double-gland system where one gland secretes the glue and another secretes a de-adhesive to sever the connection. They do not have a circulatory system, but do have a nervous system with ganglia (Ramel 2008). Like many microscopic animals, their locomotion is primarily powered by hydrostatics.
Gastrotrichs are acoelomate—that is, they have no true coelom (body cavity). Originally they were thought to have a body cavity (pseudocoel), but this was an artifact created by preservation methods, and they are now known to be acoelomate.
Gastrotrichs demonstrate eutely, with a fixed number of cell (biology) cells within a species. That is, development proceeds to a particular number of cells, and further growth comes only from an increase in cell size.
=Habitat
All species of Gastrotricha live in aquatic environments, both freshwater and saline ecosystems. Most fresh water species are part of the periphyton (mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces) and benthos (organisms which live on or in the bottom of water bodies), with presence to a lesser extent in the plankton (organisms that drift in bodies of water) (Todaro 2006). Marine species are found mostly interstitially in between sediment particles.
There can be very high concentrations of gastrotrichs in aquatic ecosystems. In freshwater, the population density may attain 158 individuals per ten square centimeters, ranking this taxon among the five most abundant taxa (Todaro 2006). In marine sediments, the density of gastrotrichs may reach 364 individuals per ten square centimeters, placing them third in abundance after the nematodes (Nematoda) and the harpacticoid copepods (Harpacticoida) (Todaro 2006).
and they reproduce entirely by parthenogenesis. Their relationship to other phyla is unclear. Morphology suggests that they are close to the Gnathostomulida, the Rotifera, or the Nematoda. On the other hand genetic studies place them as close relatives of the Platyhelminthes, the Ecdysozoa or the Lophotrochozoa. About 700 species have been described. The average life span of a gastrotrich is very short - about three days.
Classification
See 88 for suborders, subfamilies, and subgenera
- Order Chaetonotida Remane, 1925
- Family Chaetonotidae Gosse, 1864
- Genus Arenotus Kisielewski, 1987
- Genus Aspidiophorus Voigt, 1903
- Genus Caudichthydium Schwank, 1990
- Genus Chaetonotus Ehrenberg, 1830
- Genus Diuronotus Todaro, Balsamo & Kristensen, 2005
- Genus Fluxiderma d'Hondt, 1974
- Genus Ichthydium Ehrenberg, 1830
- Genus Halichaetonotus Remane, 1936
- Genus Heterolepidoderma Remane, 1926
- Genus Lepidochaetus Kisielewski 1991
- Genus Lepidodermella Blake, 1933
- Genus Musellifer Hummon, 1969
- Genus Polymerurus Remane, 1926
- Genus Rhomballichthys Schwank, 1990
- Genus Undula Kisielewski 1991
- Family Dasydytidae Daday,1905
- Genus Anacanthoderma Marcolongo, 1910
- Genus Chitonodytes Remane, 1936
- Genus Dasydytes Gosse, 1851
- Genus Haltidytes Remane 1936
- Genus Ornamentula Kisielewski 1991
- Genus Setopus Grünspan, 1908
- Genus Stylochaeta Hlava, 1905
- Family Dichaeturidae Remane, 1927
- Genus Dichaetura Lauterborn, 1913
- Family Neodasyidae Remane, 1929
- Genus Neodasys Remane, 1927
- Family Neogosseidae Remane, 1927
- Genus Neogossea Remane, 1927
- Genus Kijanebalola Beauchamp, 1932
- Family Proichthydidae Remane, 1927
- Genus Proichthydium Cordero, 1918
- Genus Proichthydioides Sudzuki, 1971
- Family Xenotrichulidae Remane, 1927
- Genus Draculiciteria Hummon, 1974
- Genus Heteroxenotrichula Wilke, 1954
- Genus Xenotrichula Remane, 1927
- Family Chaetonotidae Gosse, 1864
- Order Macrodasyida Remane, 1925
- Family Dactylopdolidae Strand, 1929
- Genus Dactylopodola Strand, 1929
- Genus Dendrodasys Wilke, 1954
- Genus Dendropodola Hummon, Todaro & Tongiorgi, 1992
- Family Lepidodasyidae Remane, 1927
- Genus Cephalodasys Remane, 1926
- Genus Dolichodasys Gagne, 1977
- Genus Lepidodasys Remane, 1926
- Genus Megadasys Schmidt, 1974
- Genus Mesodasys Remane, 1951
- Genus Paradasys Remane, 1934
- Genus Pleurodasys Remane, 1927
- Family Macrodasyidae Remane, 1926
- Genus Macrodasys Remane, 1924
- Genus Urodasys Remane, 1926
- Family Planodasyidae Rao & Clausen, 1970
- Genus Crasiella Clausen, 1968
- Genus Planodasys Rao & Clausen, 1970
- Family Thaumastodermatidae Remane, 1927
- Genus Acanthodasys Remane, 1927
- Genus Diplodasys Remane, 1927
- Genus Hemidasys Claparède, 1867
- Genus Platydasys Remane, 1927
- Genus Pseudostomella Swedmark, 1956
- Genus Ptychostomella Remane, 1926
- Genus Tetranchyroderma Remane, 1926
- Genus Thaumastoderma Remane, 1926
- Family Turbanellidae Remane, 1927
- Genus Desmodasys Clausen, 1965
- Genus Dinodasys Remane, 1927
- Genus Paraturbanella Remane, 1927
- Genus Prostobuccantia Evans & Hummon, 1991
- Genus Pseudoturbanella d'Hondt, 1968
- Genus Turbanella Schultze, 1853
- Family Xenodasyidae Todaro, Guidi, Leasi & Tongiorgi, 2006
- Genus Chordodasiopsis Todaro, Guidi, Leasi & Tongiorgi, 2006
- Genus Xenodasys Swedmark, 1967
- Incertae Sedis
- Genus Marinellina Ruttner-Kolisko, 1955
- Genus Redudasys Kisielewski, 1987
- Family Dactylopdolidae Strand, 1929
ReferencesISBN links support NWE through referral fees
- Integrated Taxonomic Information System (ITIS). 2006a. Gastrotricha Metschnikoff, 1865 ITIS Taxonomic Serial No.: 57597. Retrieved June 5, 2008.
- Integrated Taxonomic Information System (ITIS). 2006b. Chaetonotida Remane, 1924 ITIS Taxonomic Serial No.: 57822. Retrieved June 5, 2008.
- Integrated Taxonomic Information System (ITIS). 2006c. Macrodasyida Remane, 1924 ITIS Taxonomic Serial No.: 57598. Retrieved June 5, 2008.
- Ramel, G. 2008. The Phylum Gastrotricha. Earth-Life Web Productions. Retrieved June 5, 2008.
- Todaro, M. A. 2006. Gastrotricha: Overview]. University of Modena and Reggio Emilia. Retrieved June 5, 2008.
- Todaro, M. A. 2008. Gastrotricha: Systematics. University of Modena and Reggio Emilia. Retrieved June 5, 2008.
External links
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