Morphological and anatomical differentiation of three land snails of the genus Rhynchotrochus (Gastropoda: Pulmonata: Camaenidae)

摘要

Land snails of the Papua New Guinean camaenid genus Rhynchotrochus are described on the basis of shell shape, shell colour and banding pattern. We compared morphological and anatomical differentiation in three of the species, viz. R. albocarinatus, R. taylorianus and R. williamsi. The three species can be distinguished by their shell colour and banding pattern, as well as by their shell and reproductive morphology. Rhynchotrochus albocarinatus has a white, subglobose shell with up to five bands and a white to chocolate-brown outer lip. The penis is longer than the vas deferens and the length of the oviduct (LO) is approximately one-third that of the vagina. The subdepressed, trochiform shell of R. taylorianus is highly variable with respect to shell colour and banding pattern. The penis is approximately as long as the epiphallus and shorter than the vas deferens; the LO is approximately two-thirds that of the vagina. Rhynchotrochus williamsi has a white, unbanded, globose shell with a white to light pink outer lip and a dark protoconch. The penis is markedly shorter than the vas deferens or epiphallus which are approximately of the same length; the oviduct is approximately half as long as the vagina. Within R. taylorianus, there is substantial variation in shell colour, shell banding pattern and reproductive morphology that may confuse identification. We also document on one specimen of R. albocarinatus that has two interconnected penises. Since both penises were not connected to the spermoviduct, copulation as a male should have been prevented in this specimen.