DESICCATION TOLERANCE OF THE BARNACLE SEMIBALANUS-BALANOIDES (L) IN RELATION TO SHORE HEIGHT (CIRRIPEDIA, THORACICA)

The desiccation tolerance of the barnacle Semibalanus balanoides was i nvestigated in the laboratory. Barnacles were collected from three lev els (approximately MLWN, MTL and MHWN) on a shore in the Isle of Man, and the median lethal time under conditions of 20 degrees C and 15% RH determined. For barnacles of the same opercular diameter the median l ethal time was significantly longer at higher shore levels. Compared w ith low-shore barnacles the median lethal time was approximately 40% l onger for mid-shore and 70% longer for high-shore barnacles. The relat ionship between water content and opercular diameter was examined, and barnacles from the three shore levels showed no differences. Therefor e it is thought probable that the difference in desiccation tolerance is due either to differences in behaviour affecting rate of water loss , or differences in tolerance of water loss.