First record of rare dasydytid gastrotrich Setopus tongiorgii (Balsamo, 1982) from central Europe with some biological data

Abstract

Members of the freshwater family Dasydytidae belong to the rarest gastrotrichs although some species like Stylochaeta scirtetica may develop high population densities (Schwank 1990). The taxon Dasydytidae is characterised by several apomorphic features correlated to a semi-planktonic lifestyle. Species of Dasydytidae have, for example, completely lost their caudal adhesive tubes, they possess a system of ciliary bands in the head region with which they swim like ciliated larvae of annelids, and most species have motile spines to perform saltatory movements in the water column. So far, our knowledge on the biology, life cycle and their distribution is very limited. This is probably due to the rareness and difficult preparation and handling of Dasydytidae.