THE BEHAVIOR OF NEPHTYS CECA INSIDE SEDIM ENT UNDER EXPERIMENTAL CONDITIONS

The spontaneous displacement inside sediment was clearly demonstrated in Nephtys caeca Fabricius (Polychaeta: Nephtyidae). The burrowing spe ed varies from 0.18 to 0.75 cm.s(-1) and an individual covers, in aver age, between 12.1 and 27.1 cm.d(-1) in the surface sediment layer (dep th < 10cm). Daily mean horizontal distance increases as a function to sea water temperature. Daily minimal distance increases while maximal distance decreases when a reduction of sea water temperature is observ ed. The Nephtys caeca's behaviour in the sediment appears to be differ ent than Nereis virens and probably contributes to maintain of coexist ence between these main infaunal predators. Moreover, our results show , for the first time, a predatory behaviour that confirms the carnivor ous feeding trends of N. caeca species.