Interstitial fauna of the Galapagos: Porrocystidinae (Platyhelminthes Polycystididae)

Abstract

Three new species, from the Galapagos Isles, of the ill-defined taxon Porrocystidinae Evdonin 1977 are described. Austrorhynchus galapagoensis n. sp. is mainly characterized by the shape of the male accessory organ. The other two species represent new genera: Galapagorhynchus hoxholdi n. gen. n, sp. and Pygmorhynchus pygmaeus n. gen. n. sp. The main characteristics of Galapagorhynchus n. gen. are the presence of hard teeth in the male atrium, the lack of an accessory stylet, the long spermatic duels and the very elongated common genital atrium. Pygmorhynchus n. gen. lacks an accessory stylet, has short but strongly muscular spermatic ducts and has nuclei near the junction of the epithelia of the proboscis sheath and cone. The systematic positions of the three new taxa are discussed, and a brief phylogenetic analysis of the Porrocystidinae is given. Diagnoses of the new taxa are given, and the diagnosis of the subfamily Porrocystidinae is emended.