Spontaneous and induced components of salinity preference behaviour in Carcinus maenas

Abstract

Mark and recapture experiments showed that shore crab Carcinus rnaenas in an estuary were capable of remaining there for at least 6 d and were potentially exposed to extreme changes in salinity over successive tidal cycles. Behavioural responses of C. maenas to sahnity were studled in choice-chamber experiments, in some of which locomotor activity and a crab's position in the cholce chambers were recorded continuously. In multiple-choice and 2-choice experiments, crabs responded to sal~nity differences of as little as 4 to 6%0 S over a period of 4 to 5h. C. rnaenas has a 'preferred' salinity range with a lower limit of about 27 %O avoidance behaviour in the form of sustained halolunesis, though this was exhibited most markedly when both salinities offered were below about 17 %O S avoidance of S (E 80 % SW), which is shown to be achieved partly by S. In the salinity range 17 to 27 %O the lower salinity in a pair offered appears to follow mainly from the spontaneous pattern of locomotor activity, which occurs even in controls when crabs are presented with water of 34 %O choice chamber. S in each half of a INTRODUCTION