The gastrotrich community of a northAdriatic Sea site, with a redescription of Musellifer profundus (Chaetonotida: Muselliferidae).

During a survey of the marine meiobenthos in a predominantly muddy area, 40 km south of Venice (northern Adriatic Sea,Italy), 11 species of gastrotrichs were recorded. Gastrotrichs were found in 11 out of the 16 investigated stations, with densities(mean + standard deviation) ranging from 0.6 + 0.5 to 97.7 + 71.2 ind./10 cm2. The community was dominated byMusellifer profundus, which made up 24.5% of the entire gastrotrich assemblage and reached in a single station the abundancepeak of 18.3 ind./10 cm2. The finding bears relevance to the biogeography and ecology of several species. The presence ofnumerous specimens of the rare M. profundus allowed new insights into the arrangement and functioning of the hermaphroditicsexual apparatus in this phylogenetically important genus, for which such data are scanty. The new information willcertainly be useful in evolutionary studies aimed at reconstructing the phylogenetic relationships within Gastrotricha, whileoffering at the same time additional morphological traits to be used in reliable species identification. Although only threespecies of Musellifer have been described so far, there are several others awaiting a formal affiliation, a task that willbenefit from this new information.