抄録
Abstract: The distribution of the herbivorous gastropods Chlorostoma lischkei and Omphalius pfeifferi pfeifferi in relation to the algal community was investigated on a rocky shore of the Oshika Peninsula, north eastern Japan. Chlorostoma lischkei was distributed chiefly in a shallower cobble area all year round while O. p. pfeifferi lived always in the Eisenia bicyclis forest. Detailed microhabitat surveys showed that smaller C. lischkei individuals inhabited the undersides of cobbles and the bottom beneath cobbles, and that larger ones migrated to more exposed places. Larger O. p. pfeifferi individuals inhabited the laminae of E. bicyclis, medium-sized ones the holdfasts of E. bicyclis, and smaller ones the sea bottom under cobbles. Avoidance of predation is probably why smaller individuals of both species commonly lived beneath cobbles. With growth, O. p. pfeifferi utilized E. bicyclis not only as food but also as the main living space, but C. lischkei did not form such a relationship with algae. This indicates a fundamental difference between the two species in their relationships with algae and algal vegetation.
