Shell shape and mating behaviour in pulmonate gastropods (Mollusca)

Abstract

Previous work suggests that low-spired hermaphroditic snails mate face-to-face and have reciprocal sperm exchange, whereas high-spired snails mate by shell mounting and have unilateral sperm exchange. This dichotomy lead others to speculate on the evolution of enigmatic mating behaviours and whole-body enantiomorphy. In the present study, we review the current literature on mating behaviour in pulmonate snails and show that: (1) several pulmonate species show considerable intraspecific variation in mating behaviour; (2) mating position does not predict reciprocity of penis intromission and sperm exchange; (3) dart-shooting may be correlated with reciprocity of sperm exchange but other factors must explain the gain or loss of darts; (4) it is unlikely that the degree of reciprocity is the most important factor in explaining the relationship of whole-body enantiomorphy and shell shape; and (5) the reciprocal intromission of penises does not necessarily involve the reciprocal transfer of sperm. Hence, our survey shows that current ideas on the evolutionary relationship between shell shape and reciprocity with sexual selection (including dart-use) and whole-body enantiomorphy in hermaphroditic snails should be refined. The results obtained demonstrate that our current knowledge on gastropod mating behaviour is too limited to detect general evolutionary trajectories in gastropod mating behaviour and genital anatomy.

Sistema reproductivo, comportamiento de apareamiento y ecología básica de un caracol tropical extremadamente raro: Drymaeus tripictus (Stylommatophora: Bulimulidae)

“…Mating of D. tripictus is unilateral, by shell mounting, without role switching and with cryptic phallus intromission. This fits with what is generally expected for high-spired shell species, except for the fact that I did not observe the role switch (Jordaens et al, 2009).…”

“…It is reported as being simple externally and complicated internally, and as having a short flagellum and carrefour with multiple sperm storing tubules (Solem, 1955;Van Mol, 1971;Breure, 1974;Beese, 2007;Beese et al, 2009). Nevertheless, the mating behavior is not known and their mode of phallus intromission is unknown (Jordaens, Dillen, & Backeljau, 2009).…”

Burrowing in the Freshwater MusselElliptio complanatais Sexually Dimorphic and Feminized by Low Levels of Atrazine

“…Sexually dimorphic movement behavior is well known in other animals, from mammals (Smale et al, 1997), to insects (Martin, 2004), thus it is not terribly surprising to find the same in bivalves. Sexual dimorphisms in reproductive behavior were reported for other mollusks (Jordaens et al, 2009) and there are recent reports of sexually dimorphic shell shapes in freshwater mussels, including other Unionids (Widarto, 2009; Zieritz and Aldridge, 2011). Thus, this study of gender-specific movement behavior in E. complanata is also an extension of previous knowledge on bivalve sexual dimorphisms.…”

High gene flow despite opposite chirality in hybrid zones between enantiomorphic door snails

“…Reversals of the primary asymmetry in spiral gastropods may affect gene flow because the position of the genital orifice on different body sides in clockwise (dextral) and counterclockwise (sinistral) coiled snails can impede mating of enantiomorphs (Asami, Cowie, & Ohbayashi, 1998;Johnson, 1982;Ueshima & Asami, 2003). The restriction of gene flow associated with opposite coiling direction depends on the mating behaviour, which is associated with shell shape (Asami et al, 1998;Davison, Wade, Mordan, & Chiba, 2005;Jordaens, Dillen, & Backeljau, 2009). In snail species with flat or globular shells that usually mate reciprocally face-to-face, matings of enantiomorphs are very rare because the genitalia are exposed to different body sides and cannot be joined.…”