Female preference for large waving claws in the dotillid crab Ilyoplax pusilla

Male Ilyoplax pusilla perform a waving display, a simple up-down movement of the claws during the reproductive season. Large males dedicated most of their surface activity to waving displays and gained higher mating success. On the other hand, small males infrequently performed waving displays and devoted their time exclusively to foraging. To examine female preference for the size of waving males, two female-release experiments were conducted. In the experiments, we recorded female choice between small- and large-waving claw models over short (10 cm) and long (25 cm) distances. In both the short- and long-distance choice experiments, significantly more females chose the large-claw model over the small-claw model. The following characteristics may produce obvious age-dependent sexual advertisement in I. pusilla, which grows throughout a life: (1) the strong female preference for large claws; (2) the short, 2-year lifespan that includes only two reproductive seasons; and (3) the lack of alternative mating strategies (e.g., surface mating).