Comportamento predatório do caranguejo Menippe nodifrons Stimpson, 1859 (Decapoda: Brachyura: Menippidae) sobre moluscos gastrópodes em laboratório

Abstract

Laboratory experiments were used to study the effect of the predation of the crab Menippe nodifrons on the gastropods Stramonita haemastoma, Tegula viridula and Neritina virginea. Aspects studied were prey preference, handling time, predation techniques, prey critical size and chelal biomechanic analysis of the crabs. The crabs and the clams were collected in Pacheco beach, located in the city of Caucaia-Ce. Menippe nodifrons preferred Neritina virginea over both Stramonita haemastoma and Tegula viridula, and Stramonita haemastoma was strongly preferred over Tegula viridula, possibly because of differences in shell characteristics among the three species. The male crabs preyed more heavily upon Neritina virginea than on both gastropods Stramonita haemastoma and Tegula viridula, while the females had eaten indistinctly the three clams. There were differences in hadling times between Neritina virginea, Stramonita haemastoma and Tegula viridula (handling times: N. virginea < S. haemastoma < T. viridula). Crabs attacked snails using crushing and peeling techniques, the last was used only upon S. haemastoma and T. viridula. The mean critical size for Neritina virginea was significantly smaller than that for Stramonita haemastoma, which in turn was smaller than that for Tegula viridula. The claws of the crab Menippe nodifrons are well designed for breaking shells. Menipppe nodifrons is heterochelous, having one larger crusher claw and one smaller less robust cutter claw. Due to their greater mechanical advantage, crusher claws are able to generate considerably greater forces than cutters. Differences in the morphological and mechanical features of crab claws reflect their function and account for many of the observed differences in prey handling techniques and foraging behavior. Menippe nodifrons seems to be specialised for attacking hardshelled molluscan prey. The predatory behavior of the crab Menippe nodifrons is directly related to the level of specialization of its claws, of the morphological characteristics and vulnerability of its prey items.