Mucus trail following as a mate-searching strategy in mangrove littorinid snails

Mate searching often involves chemical cues and is a key process in determining fitness in most sexually reproducing animals. Effective mate-searching strategies are, therefore, essential for individuals to avoid wasting resources as a result of misrecognition of mating partners. Marine snails in the genus Littoraria are among the most successful molluscan groups that live closely associated with mangroves. Their population densities are often low, and finding a mate within the complex three-dimensional habitat of tree leaves, branches and trunks requires an effective searching strategy. We tested whether males of L. ardouiniana and L. melanostoma located females by following their mucus trails. In the laboratory, male tracker snails followed mucus trails laid by conspecific female marker snails at a higher intensity compared with other marker–tracker sex combinations in the mating season, but not in the nonmating season, and this was more pronounced in L. ardouiniana. Male trackers did not move faster when following the trails of conspecific female markers compared with other sex combinations; however, tracker snails moved faster in the mating than in the nonmating season, although this might be related to temperature. In both species, males tracked females regardless of trail complexity, and the majority of male trackers were able to detect the direction (polarity) of the trails of conspecific females. Together with previous studies on rocky shore Littorina species, these findings suggest that sex pheromones are incorporated into mucus trails to facilitate the reproductive success of these snails. Mucus trail following is, therefore, an adaptive mate-searching strategy in intertidal gastropod molluscs, and potentially in other gastropod groups in which trail-following behaviour is prevalent.