Copulation of the Japanese potamid crab Geothelphusa dehaani in their natural habitat

Abstract

Mating pairs of the potamid crab Geothelphusa dehaani were observed in a mountain stream of Fukuoka Prefecture, Japan, during the survey of over ca. 3-year period. Five mating pairs in copulatory posture were found in the afternoon in October and November. Mating pairs remained immobile for at least several minutes. No guarding behavior was observed after the release of copulation. They were all found on the bottom substrate under the water in pools. Females were either in the soft-shell or hard-shell condition, and even included one juvenile among the adults.