BEHAVIOR AND HEMOLYMPHATIC IONIC COMPOSITION OF THE INTERTIDAL CRAB CHASMAGNATHUS-GRANULATA DANA, 1851 (CRUSTACEA, DECAPODA) DURING EMERSION

1. Behavioural observations and haemolymphatic measurements of Na+ Kand Ca2+ were performed in Chasmagnathus granulata during emersion. 2. Activity levels were found to be higher during voluntary emersion per iods than when the animals were submerged. A LT50 of 39.45 hr was obse rved when no access to water was allowed. 3. The Na+ and K,+ and Ca2levels increased during aerial exposure. The Na+ and K+ levels were re stored prior the end of the experimental period. Mechanisms for such r egulation are therefore discussed. The Ca2+ levels, remaining high dur ing emersion, are probably a result of acid-base balance adjustments.