SPAWNING ACTIVITY IN NODILITTORINA EXIGUA AND PEASIELLA ROEPSTORFFIANA (LITTORINIDAE, GASTROPODA)

Abstract

Periodicity in spawning was studied for the two species of Littorinidae, Nodilittorina exigua and Peasiella roepstorffiana at Shirahama, Wakayama Pref. Breeding season of N. exigua is summer, active spawning being associated with strong waves and not with spring tides. Egg release is active at around high tides in the field and this habit is preserved for some time in the laboratory. Peasiella roepstorffiana also spawns in summer and its active spawning is related to both lunar phase and daily tidal cycle. The difference in spawning habit is related to the difference in the distribution height of these species under the influence of the tidal regime in upper littoral zone.