Mating strategies of the endangered insular land crab Johngarthia lagostoma (H. Milne Edwards, 1837)

Abstract

Hard-shell-mating is the typical way that semi-terrestrial and terrestrial crabs copulate, when females reproduce with a hard carapace during the intermoult period and the couples have a brief or absent pre- and post-copulatory behaviour. For Gecarcinidae crabs there are few studies on reproductive behaviour, and are especially rare for isolated species, as in the genus Johngarthia. Here, we describe the mating behaviour of the endangered insular crab J. lagostoma endemic of the South Atlantic Ocean, with a focus on pre-, copulatory, and post-copulatory behaviours. Observations were made on 20 pairs in the field, with every female in intermoult. Accessory behaviours were absent, with copulation beginning after sexual recognition. After mating, there were no records of males guarding or embracing females. All couples had the female in an upper position and passive males, which do not react when other males are near the mating site. The size of the chelipeds and males were random and not determinant to mating. However, yellow crabs predominated (95%) in mating pairs and the linkage of colouration to sexual selection needs to be more elucidated because purple crabs are less frequent in the population and the lower representation in the couples can be an effect of this. Experimental studies are required to investigate sexual selection and the occurrence of the behaviour described herein at other locations.