The description of wandering behavior and its occurrence varying in different tidal areas in MacrophthalmusJaponicus (De Haan) (Crustacea : Ocypodidae)

Abstract

Some characteristics of wandering Macrophthalmus japonicus (De Haan) and the mechanism of wandering were studied at two sites, Station A (St.A) where crabs did not wander and Station B (St.B) where wandering occurred. From mid-June to mid-September, many wanderers were observed along the water's edge at St.B. The number of wanderers clearly followed a semi-lunar cycle with a peak near spring tide. Most wanderers were large crabs and the percent of ovigerous females was low. In the wandering season, feeding activity of burrow owners at St.B. declined during the time of low tide, but at St.A. feeding activity of burrow owners was more pronounced and almost equal to that of wanderers at St.B. The water content of the substratum during low tide in the burrow area at St.B. (St.B-b) was significantly lower than that at St.A and the wandering area of St.B. Nitrogen content of the substratum in St.A was not significantly higher than that in St.B-b. Crab density at St.B. was not significantly higher than at St.A. It was concluded that the wandering was due to poor water supply in the burrow area, since water is indispensable for feeding and respiration during low tide.