Mating behaviour and copulatory mechanics in six species of Planorbidae (Gastropoda: Pulmonata)

Abstract

Although Planorbidae are one the most common and diverse families of pulmonates, their mating behaviour is known only for a few species. This paper describes mating behaviour and copulatory mechanics in four species of the Planorbidae: Anisus vortex (Linnaeus, 1758), Bathyomphalus ontortus (Linnaeus, 1758), Choanomphalus riparius (Westerlund, 1865) and Planorbis planorbis (Linnaeus, 1758), and supplements previously published observations on two other species: Segmentina oelandica (Westerlund, 1885) and Planorbella (Seminolina) duryi (Wetherby, 1879). Patterns of musculature of the penial complex [in all species except P. (S.) duryi] were studied using fluorescent phalloidin dye specific for actin filaments. Choanomphalus riparius, P. planorbis and S. oelandica were shown to mate by shell mounting and display an elaborate courtship behaviour accompanied by shell-circling. Planorbella (S.) duryi mates in a face-to-face position; in this species, courtship is accompanied by mechanical stimulation of the partners plicae. Anisus vortex and B. contortus do not exhibit any distinct precopulatory behaviour and mate face-to-face. It is argued that Planorbidae show a relationship between gender expression (functional protandry vs simultaneous hermaphroditism) and mating behaviour (unilateral vs reciprocal mating). The taxonomic utility of the copulatory behaviour and penial musculature is discussed. © 2012 The Author.