The neglected operculum: a revision of the opercular characters in river snails (Caenogastropoda: Viviparidae)

Abstract

The morphological identification of many groups of gastropods is mostly based on shell morphology and genital structures. The value of opercular characters as taxonomic characters has so far been barely studied and evaluated. Here, the opercular characters of river snails (Viviparidae) have been revised systematically for the first time. Based on a morphological study of the opercula of 38 species of 25 viviparid genera, 16 newly defined opercular characters are shown to be useful for genus and species identification. A detailed diagnosis and description of opercular characters for each genus/species is given. One new generic assignment of a viviparid species is proposed based on this study, namely Cipangopaludina nagaensis n. comb.

Rediscovery and systematics of the enigmatic genus Helicostoa reveals a new species of sessile freshwater snail with remarkable sexual dimorphism

“…The snail bodies, male genitals and egg capsules were taken out during dissection and photographed under a stereomicroscope (Leica MDG34 or Nikon SMZ18). The operculum has been described according to Zhang & von Rintelen [17].…”