Interstitial fauna of the Galapagos: Duplacrorhynchinae, Macrorhynchinae, Polycystidinae, Gyratricinae (Platyhelminthes Polycystididae)

Abstract

Seven species from the Galapagos of different subfamilies of the Polycystididae are described and discussed. Four of them are new to science, three of which belong to the subfamily Duplacrorhynchinae Schockaert & Karling 1970: Dieziraia incana n. sp. differs from the other species of the genus by its long, thin stylet; Phonorhynchoides haegheni n. sp. is unique within the genus, as the prostate stylet is much shorter than the accessory stylet; Parachrorhynchus jondelii n. sp. is characterised by the presence of a bundle of atrial glands, paired seminal vesicles, a very large sphincter at the distal end of the female duct, and a ring of hard plates at the distal end of each ovary. Of the Macrorhynchinae Evdonin 1977, Macrorhynchus manusferrea n, sp. differs from the other species of the genus by the shape of the stylet and the presence of a female bursa. The subfamily Polycystidinae Schockaert & Karling 1970 is represented by Polycystis ali Schockaert 1982 and Paulodora felis (Marcus 1954). The Galapagos population of the latter species is considered a separate subspecies, P. felis asymmetrica n. subsp., based on differences in the female system. Finally, Gyratrix hermaphroditus Ehrenberg 1831 is discussed. Three colour variants of this species complex are found in the Galapagos, which represent three more species in the complex. For all new taxa, a diagnosis is given. At the end, we provide a species list of the polycystidid fauna of the Galapagos Isles.