Distribution of Two Rare Species of Brackish-water Crabs, Deiratonotus kaoriae and D. cristatus (Camptandriidae), in the Kushida River Estuary, Mie Prefecture, Japan

Abstract

The distributions of two closely related camptandriid crabs, Deiratonotus kaoriae and D. cristatus, were investigated in the Kushida River Estuary (Mie Prefecture, Japan) in October, 2008. The two species were distributed differently, with D. kaoriae in the lower reaches and D. cristatus in the upper reaches of the estuary. The physico-chemical environmental conditions of these areas differed in that the areas inhabited by D. kaoriae had a higher water temperature, higher salinity, and higher elevation than those inhabited by D. cristatus. The substrata of the two crabs’ habitats were also different, being dominated by sand in the case of D. kaoriae, but by mud in the case of D. cristatus. The presence of percolating ground water in the substratum was common to the habitat of both species.