抄録
Monodonta labio (Linné) is a common species on intertidal rocky shores along the Pacific coast of the Boso Peninsula, Honshu, Japan. The study area for this research consisted of bed-rock and cobble-field habitats. Seasonal changes in size distribution in these two habitats, including juveniles, were investigated from April, 1989 to April, 1991. These results showed that small snails concentrated in the cobble-fields, and larger individuals on the bed-rock. To determine the cause of this difference in size distribution, mark-recapture experiments were conducted from April, 1990 to April, 1991. Juvenile snails were shown to recruit only in the cobble-fields, and larger snails more than about 5 mm to migrate from the cobble-fields to bed-rock, mainly during late autumn to winter. This growth-related migration may be an adaptive strategy for utilizing a rocky shore with a variety of microhabitats.
