Behavioural responses of Carcinus mediterraneus Czerniavsky, 1884 to changes in salinity

Abstract

Behavioural mechanisms were considered whereby Carcinus mediterraneus populations are maintained in the deltaic bays of the Ebro Delta, E Spain, at salinities in the range of 23-35 ppt and are absent from 38 ppt seawater in the adjacent Mediterranean Sea. When exposed experimentally to cycles of salinity change from 38 ppt to 17 ppt, C. mediterraneus responded with increased locomotor activity as salinity increased and decreased around a value of approximately 23 ppt. It is suggested that these responses permit the avoidance of freshwater and of full seawater at 38 ppt in the open Mediterranean. Carcinus mediterraneus exhibit only circadian, not circatidal, free-running locomotor rhythmicity which is uninfluenced by simulated tidal cycles of salinity change. (DBO)