Rhabdocoela (Platyhelminthes) from the Weddell Sea (Antarctica) with the description of eight new species

Abstract

In this contribution we present eleven species of Rhabdocoela (Platyhelminthes) collected during the Antarktis VII/4 (Epos leg. 3) expedition. Six of them belong to the family Trigonostomidae (Typhloplanoida). Five of these are new to science: Trigonostomum messoplanoides n. sp., Proxenetes trispinosus n. sp., Messoplana globulifera n. sp., M. minuta n. sp. and M. spiralis n. sp. All the species can be recognised from congeneric species by the shapes of their stylets. Ceratopera axi (Riedl, 1953) Den Hartog, 1964 also was found and is discussed briefly. The other five species belong to the family Polycystididae (Eukalyptorhynchia). Three of them are new to science and belong to the genus Austrorhynchus Karling, 1952: A. magnificoides n. sp., A. antarcticus n. sp. and A. biserratus n. sp. They differ from other Austrorhynchus species in having a triangular share of the accessory organ of the male system. Particular differences in shape of the stylet and accessory organ clearly distinguish each of the new species. Unlike the other two species, A. antarcticus lacks a hook on the stylet. The genus Austrorhynchus is briefly discussed. The collected material of Gyratrix hermaphroditus Ehrenberg, 1831 and Porrocystis assimilis (Levinsen, 1879) Karling, 1952 is also briefly discussed.