Two new genera and species of Gastrotricha are described from the psammon of a freshwater body in Brazil: Redudasys fornerise and Arenotus strixinoi. The former is the first undoubted member of the order Macrodasyida recorded from a freshwater environment. It is characterized by the reduction in number of adhesive tubes, the absence of male sexual organs and the presence of a well-developed protonephridial system. The latter belongs to the order Chaetonotida (family Chaetonotidae) and is characterized by the uniform body covering with a thick layer of soft homogeneous cuticle. A possible mode of colonization of fresh waters by marine Macrodasyida, involving colonization of freshwater areas underlying marine beaches, is discussed.

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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

Gastrotricha is a cosmopolitan phylum of aquatic and semi-terrestrial invertebrates that comprises ~820 described species. To date, freshwater gastrotrichs have not been the subject of faunistic or taxonomic research in the polar regions. In this paper, we present the first species-level description of a freshwater gastrotrich from the Arctic (Svalbard Archipelago). Evidence from morphology, morphometry and molecular analyses reveals that the species represents a new genus in Chaetonotidae: Bifidochaetus arcticus, gen. et sp. nov. Taking into consideration many morphological similarities to Chaetonotus (Primochaetus) veronicae Kånneby, 2013 we propose to include C. (P.) veronicae in the newly established genus under the new combination Bifidochaetus veronicae (Kånneby, 2013), comb. nov. In the phylogenetic analysis based on nuclear 18S rRNA, 28S rRNA and mitochondrial cytochrome c oxidase subunit I sequence data, B. arcticus, gen. et sp. nov. is nested within the family Chaetonotidae, as the sister group to the genus Lepidochaetus Kisielewski, 1991. In this paper we also present new taxonomic characters useful for gastrotrich taxonomy: the pharynx-to-intestine length ratio (I) and the spine bifurcation ratio (B).

INSTTTUT ZOOLOGII FRAGMENTA FAUNISTICA Tom 30 W arszaw a, 1086.11.15 Mr 16 Jacek K i s i e l e w s k i Freshwater G astrotricha of Poland. VII. G astrotricha of extremely eutrophicated water bodies [W ith 1 figure and 3 tables] A bstract. In extrem ely eutropliicated Avaters of Poland 71 species of Gastrotricha were found, including 50 identified ones. Eight species occurred only in this environm ent, whereas other 14 found optim um conditions there. Higher taxa as a whole are connected wdth this environ m ent: genus Polymerurus and fam ilies D asydytidae and Neogosseidae. The fauna Ava s m ost abundant in Avater bodies with the association Hydrocharitetuvi morsus-ranae. All available data on freslnvater Gastrotricha from Poland are recapitulated. The present paper is the last in a series of seven publications on Gastrotricha fauna of various environm ents of Polish inland waters. The first paper (K i s i e l e w s k i and K i s i e l e w s k a 1986-cited fu rth er in the te x t as "I ") discussed th e Gastrotricha of m ountain w aters, both oligotrophic lakes, sources and stre ams and eutrophic w ater bodies. A ltogether 32 identified species were found th e re. The second paper (K i s i e l e w s k a and K i s i e l e w s k i 1986a-cited fu rth er on as "I I ") concerns Gastrotricha of young shallow lakes of marine origin on th e B altic coast-26 species. The th ird paper (K i s i e l e w s k a and K i s i e l e w s k i 1986b-cited further on as "I I I ") deals w ith Gastrotricha of a v ast complex of prim ary forests of the Białowieża F orest and eutrophic w ater bodies of the B ia łowieża Glade-48 identified species. In th e fourth paper N e s t e r u k (1986)-ci ted further on as "IV "-describes th e Gastrotricha fauna from fish ponds near Siedlce-39 species. K i s i e l e w s k a and K i s i e l e w s k i (1986c-cited further on as "V ") present the results of investigations on Gastrotricha of alder woods-41 species. The paper before th e last (S z k u t n i k 1986-cited further on as "V I") deals with Gastrotricha of astatic w ater environm ents overgrown with rush vegatation-43 species. Altogether, in all papers, 72 identified species and forms of http://rcin.org.pl 26S J. K isielew ski Gastrotricha were found, of which 07 belong to the family Chaetonotidae and 5 to Dasydytidae. The present paper deals with the gastrotrichan fauna of highly eutrophicated water bodies. Gastrotricha of these environm ents have been already inve stigated in Poland. B o s z o z a k (1935, 1968), when investigating w ater bodies in central G reat Poland, has given a num ber of species from waters of a high degree of fertility. D ata on Gastrotricha of eutrophic w aters are given in two of m y taxonomic papers (K i s i e l e w s k i 1974, 1979); full faunistic data, p artly used in papers mentioned, have been included here. K i s i e l e w s k a (1982) lias exam ined Gastrotricha of two complexes of highly eutrophicated peat-hags near Siedlce. Finally, in some papers of th e series (III, IV and VI) d ata on Gastrotricha of this...