Mating behaviour of Macrophthalmus hirtipes (Brachyura : Ocypodidae)

We examined the mating behaviour of the New Zealand ocypodid crab Macrophth almus hirtipes in the laboratory between February and June 1998. This speci es has a discrete breeding season. Mating and moulting were not linked and only intermoult females with mobile gonopore opercula were attractive to ma les. Allometry and compatibility of gonopods and gonopores of different-siz ed crabs was investigated. Under laboratory conditions, the opercula of int ermoult females remained mobile on average for 11.4 d, but the duration of receptivity did not appear to be under female control. The operational sex ratio in the laboratory fluctuated greatly, but was always male-dominated. During the period of opercular mobility, females mated many times with seve ral different males. Matings in the absence of burrows were relatively shor t (mean duration = 23 min, max. = 122 min) and the mating behaviour of M. h irtipes lacked courtship and mate-guarding. Males used a search-intercept m ethod to acquire mates, with very low levels of intrasexual competition. Th ere was no evidence of mate preference in M. hirtipes, and males spent just as long mating with ovigerous females as with non-ovigerous ones. Although M. hirtipes has ventral-type spermathecae, as do several other ocypodid cr abs, it is unclear whether this promotes last-male sperm precedence. The ro le of burrows in modifying the mating behaviour of M. hirtipes in the field remains to be established.