Gastrotricha are an important component of the benthos and periphyton of freshwater habitats, where they can reach densities of up to 100 ind/10 cm-2. However, due to their small size and the difficulties met in their study, gastrotrichs, and especially aspects of their reproduction and ecology, are still poorly known.Gastrotricha are aschelminthes closely related to acoelomates and comprise a phylum divided into two orders: Macrodasyida and Chaetonotida. The Macrodasyida number about 240 species, all but two of which are marine or estuarine. Chaetonotida count 450 species, mainly reported in freshwater. The about 300 gastrotrich species commonly found in inland waters inhabit the water-sediment interface and the aquatic vegetation, especially in eutrophic biotopes, but can occur in the interstitial environment.Some 70 species have been reported from psammic habitats both in lentic and lotic sediments, although less than half of these have been found in running waters. All but two freshwater gastrotrich species belong to the order Chaetonotida, which includes five families and twenty genera Sixteen of these are known exclusively from inland waters, whereas the others include both marine and freshwater species. The most numerous genus is Chaetonotus with 150 freshwater species, for which several taxonomical subdivisions have been. The considerable morphological variability of most freshwater chaetonotids often makes specific identification difficult, and consequently the taxonomy is currently unstable. Recently, a freshwater species belonging to the marine Macrodasyida order (Redudasys fornerisae) was reported by J. Kisielewski in a lentic, interstitial habitat in Brazil. In the same paper, Kisielewski reaffiliates Marinellina flagellata, a rare macrodasyid-like species found only once in running waters in Austria to Macrodasyida.A taxonomic key to worldwide freshwater gastrotrich genera, modified and simplified from those available in the literature is given below.
|Data di pubblicazione:||2002|
|Autori:||BALSAMO M.; TODARO M.A.|
|Titolo del libro:||Freshwater Meiofauna: Biology and Ecology|
|Nome editore:||Bachhuys Publishers|
|Appare nelle tipologie:||Capitolo/Saggio|
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