A comparative study of mating and copulatory mechanics in Hippeutis complanatus and Segmentina oelandica (Gastropoda: Pulmonata)

Abstract

Recent studies on mating and copulation in pulmonates have provided a better understanding of a functional relationship between various aspects of their biology and have greatly advanced our knowledge of their reproductive behaviour. Here we describe the mating behaviour, copulatory mechanics and genital anatomy of Hippeutis complanatus (Linnaeus, 1758), a Palaearctic freshwater pulmonates, and compare these results with those from Segmentina oelandica (Westerlund, 1885). In H. complanatus, the individual that initiates mating mounts the shell of the partner and crawls over its basal side to position itself at the shell aperture for intromission. The copulatory connection is achieved by the preputium and its musculo-glandular appendage (preputial organ) that attaches to the shell of the partner. Hippeutis complanatus and S. oelandica share a number of common traits in genital morphology and mating behaviour, most notably the unilateral copulation and the use of the preputial organ as a holdfast. These species also show some significant differences: the opposite orientation of the partners, chemical stimulation in S. oelandica and a significantly longer mating duration in H. complanatus. Overall, the mating behaviour of the two species shows a combination of shared and divergent traits that have potential of being useful as taxonomically informative characters.