Reproduction and genetic parentage in a pair-living hermaphrodite, the intertidal limpet Siphonaria gigas

Abstract

Pair-living is a common social system found across animal taxa, and the relationship between pair-living and reproduction varies greatly among species. Siphonaria gigas, a hermaphroditic pulmonate gastropod, often live in pairs in the rocky intertidal. Combining genetic parentage analysis using four polymorphic microsatellite loci with behavioral observations from a 10-week field study, I provide the first description of the mating system of a Siphonaria species incorporating genetic data. S. gigas mated both within-pair and extra-pair and three out of four paired S. gigas individuals produced egg masses with extra-pair paternity. Multiple paternity was detected, but at a relatively low frequency (19% of egg masses) compared to other marine gastropods. Behavioral data indicate one potential advantage of pair-living: paired S. gigas produced almost twice as many egg masses as their solitary counterparts over four reproductive cycles. These observations, together with constraints on the movement of S. gigas, suggest that pairing may be a strategy to ensure mate access.