Global diversity of gastrotrichs (Gastrotricha) in fresh waters

Abstract

The global diversity of inland water Gastrotricha is poorly known, and information is extremely heterogeneous. Gastrotricha have been studied most widely in Europe and America, whereas data from the other continents are scattered or not even available. This scanty information is related to several reasons, first of which is the technical difficulty in collecting and studying microscopic and soft-bodied species. In addition, the research has been limited mostly to the epibenthos and periphyton in lentic waters, and the gastrotrich taxonomy is still under discussion mainly because of the great intraspecific variability. Three of the five freshwater families are widespread or cosmopolitan, and most genera have been reported from at least two continents. There is strong evidence of a high diversity in genera and species in tropical areas. Nearly a half of the freshwater species are known from only one country or even only from one site, but the insufficient faunistic knowledge does not allow defining them as endemic. The phylogenetic relation-ships and possible evolutionary trends of inland water species of Gastrotricha are outlined

A phylogenetic approach to species delimitation in freshwater Gastrotricha from Sweden

“…At the species level 30% of the European and 50% of the South American gastrotrich, freshwater fauna appear to be cosmopolitan (Balsamo et al, 2008). Kisielewski (1991) studied the inland water gastrotrichs of Brazil and compared his findings with earlier findings in Europe.…”

Integrative taxonomy of a new Redudasys species (Gastrotricha: Macrodasyida) sheds light on the invasion of fresh water habitats by macrodasyids

“…nov., as well as the geographic origin of these specimens, we consider the specimens found in both studies as belonging to the new species. Furthermore, the putative assignment of these specimens to the genus Marinellina 10 cannot be supported with certainty due to several reasons: (a) insufficiency of the original description of the genus Marinellina 1,6,7 , (b) uncertainty about the exact position of TbA in Marinellina specimens 2 (c) absence of pharyngeal pores in Marinellina specimens, (d) geographic distance between the sampling sites of european individuals and of the specimens found by Araújo et al . 10 , respectively.…”

“…Gastrotricha is a group of aquatic, free-living microinvertebrates (80 µm to 3,000 µm in body length) divided into two orders: Macrodasyida and Chaetonotida 1–4 . The taxon Macrodasyida comprises over 350 worm-like species 5 , all interstitial in marine and estuarine habitats, except Marinellina flagellata Ruttner-Kolisko, 1955 collected from Austria, Redudasys fornerise Kisielewski, 1987 from Brazil and R. neotemperatus Kånneby & Kirk, 2017 from the U.S.A. 6–9 .…”

A synopsis of knowledge, zoogeography and an online interactive map of Brazilian marine gastrotrichs

“…The majority of macrodasyids are marine species; only four species have been reported in freshwater from the Swiss Alps, Brazilian streams and a reservoir and aquifer from the USA (Ruttner-Kolisko, 1955; Kisielewski, 1987; Garraffoni et al, 2010, 2019a; Todaro et al, 2012; Araújo, Alcantara & Garraffoni, 2013; Kånneby & Wicksten, 2014; Kånneby & Kirk, 2017). Within Chaetonotida, eight families, 32 genera with nearly 483 species (Todaro, 2019b) are interstitial or epibenthic in marine and brackish water, and 2/3 of the species live in freshwater habitats (Balsamo et al, 2008, 2014). They are tenpin-shaped and have one pair (rarely two or any) of adhesive tubes, limited to the posterior end (Balsamo et al, 2008; Kånneby & Hochberg, 2015).…”