Life History of Sand-Burrowing Amphipod

The amphipod Haustorioides japonicus KAMmmA is the dominant crustacean on the sandy beaches around southern Hokkaido. The present paper deals with the materials obtained at Omori beach, Hakodate, for 5 years from 1971 to 1976. This amphipod is found exculsively in the littoral zone from June to November, and disappears from the beach for the rest of the year by burrowing in the infralittoral zone. The reproductive season begins in early June and lasts until early August with five notable spawning periods. The generation seems to be completed within a year. The sex ratio is 1:1 during in the first half of the breeding season, but it becomes 1:2 in the latter half of the season, due to a sudden increase in deaths among male members. The regression equation of body length (L)-dry weight (W) relationship for H. japonicu8 can be expressed as W =0.0189 L2.808. Numbers of eggs per brood are 77.6±20A, with a range from 13 to 142, depending upon the body length