Activity Rhythms, Homing and Reproductive Behavior of the Intertidal Pulmonate Mollusc Peronia verruculata (Cuvier, 1830) on Sesoko Island, Okinawa

Abstract

Activity rhythms, homing and reproductive behaviors of the hermaphroditic pulmonate mollusc Peronia verruculata (Cuvier, 1830) were investigated on a rocky intertidal zone on Sesoko Island (26°38′N, 127°54′E), Okinawa. The molluscs stayed in holes in the rock while the habitat was submerged or washed with seawater. Animals emerged and were active only when their habitats were completely exposed. All individuals showed homing behavior. The number of emerged individuals, the distance moved and the duration of excursions were inversely related to the lowest tidal level at ebb tide. Animals that emerged were fewer and less active at night than during daytime. Initial courtship of individuals as males was seen 21 times, and in 5 cases copulation occurred. Peronia verruculata (Cuvier, 1830) played a positive role as males but a passive role as females in courtship behavior and copulation.