Abstract

The present paper deals with the breeding ecology of two dogielinotid amhipods on the five sandy-beaches in southern Hokkaido. Japan. Haustorioides japonicus and H. munsterhjelmi are semelparity species. The peaks of egg-laying in H. japonicus population on the Omori-beach. Hakodate were observed four or five times in a breeding season, and these peaks synchronized with the semi-lunar cycle. In the first half of breeding season, the large size females occupied the majority in the latter half. The number of eggs per brood in both species is positively, correlated to the female body length. Mean fecundity ranges from 70 to 87 eggs in the first generation of H. japonicus, and the ranges from 84 to 106 eggs in H. munsterhjelmi. Dogielinotid amhipods seems to be productive comparing with other gammarid families.