Sexually dimorphic claws predict courtship and mating sequence in the intertidal oribatid mite Fortuynia atlantica (Acari, Oribatida)

Abstract

Fortuynia atlantica, is a sexually dimorphic oribatid mite and although observations are lacking, direct sperm transfer is assumed. We found an additional sexual dimorphism in claw morphology, with females showing relatively smaller and more curved claws, which may point to a possible direct contact during reproduction. Males possess lateral notogastral projections and these could be used as ‘handles’ by the females in the course of some kind of mating. The claws of the females are large enough to embrace the male’s lateral projections and the females’ first legs are long enough to attach to the males’ body from behind without hampering its movement with the rest of the legs. Based on these indications, we propose a hypothetical mating scenario where the male attracts females via pheromones, the female approaches from behind and clasps with the claws of the leg I the ’handles’ of the male. This stimulates the male to deposit a stalkless spermatophore and in a final step the male leads the still attached female over the spermatophore to absorb it. Observation of living specimens is ultimately necessary to verify the existence of the proposed or any other mating behaviour.