Reproduction of Epigrapsus notatus (Brachyura: Gecarcinidae) in Taiwan

Abstract

The population dynamics and reproduction of the land crab Epigrapsus notatus were studied at Hengchun Peninsula, Taiwan. Epigrapsus is the most poorly known genus of the land crab family Gecarcinidae, and differs from other gecarcinids in its much smaller size. Epigrapsus notatus leads a cryptic life and is seldom observed outside its burrow in the coastal forest. The only time it is commonly observed is when ovigerous females migrate to the shore to release larvae. The reproductive season of E. notatus is limited to two lunar months in September and October, a relative short time in comparison with other gecarcinid crabs. Ovigerous females begin releasing larvae 3-4 d after the full moon, for 3-7 d. Larval releases occur for about a 3-h period during and immediately after high tide. Ovigerous females shake their entire body to release larvae, a unique behavior not previously documented in brachyurans. Ovigerous females prefer to release larvae inside surge channels rather than on the exposed shore. The unusual larval release behavior and choice of surge channels as release sites are suggested as adaptations to life on land, to reduce the chances of being swept away by waves.