effect of eyestalk ablation on oxygen-consumption of callinectes-similis exposed to salinity changes

Abstract

1. The effect of eyestalk ablation on preadults of Callinectes similis exposed to a constant salinity (30 parts per thousand) and to simulated tidal changes in salinity (30-11 to 30 parts per thousand) were measured. 2. In constant salinity, crabs showed a persistent respiratory rhythm, with a maximum oxygen consumption during the day. Under these conditions, ablation significantly increased the respiratory rate but not the rhythm. 3. In variable salinities, the highest respiratory rates occurred in salinities of 11 and 16 parts per thousand during the night. In these crabs, ablation of eyestalks and subsequent injection of eyestalk extracts did not alter the respiration rate rhythm. 4. The circadian rhythm is controlled by the periodicity of environmental changes instead of the influence of eyestalk hormones. 5. Regulation of metabolism in C. similis associated with osmoregulation involves other neurosecretory organs.