Observations of hard-shell mating in the portunid crab Charybdis japonica (A. Milne-Edwards, 1861) (Decapoda: Brachyura)

Abstract

Portunid crabs characteristically undertake soft-shell-female mating, with extensive pre- and post-copulatory guarding of the female. We herein record hard-shell-female mating in the portunid Charybdis japonica (A. Milne-Edwards, 1861) in New Zealand. Mating pairs were recorded in 2014 and 2015 between August and December inclusive, with peak mating in late winter/early spring. Copulation in C. japonica was prolonged, lasting between 180 to 270 min, with no pre- or post-copulatory guarding being observed. Among members of the family Portunidae, hard-shell-female mating has only been documented in the subfamily Thalamitinae, with C. japonica the fifth species documented to utilise this mating strategy. Further investigations are warranted to determine the extent of hard-shell-female mating within other subfamilies of Portunidae.