Food availability and diel feeding rhythms in the marine copepods Acartia grani and Centropages typicus

The effects of food availability on the daily feeding pattern of planktonic copepods was studied for two species: Acartia grani (cultured and wild spe cimens) and Centropages typicus (wild specimens). Both species showed clear diel feeding rhythms at high food concentrations, with significantly highe r clearance rates during night hours. However, at limiting food conditions, while C.typicus maintained its daily feeding pattern, A.grani fed continuo usly, with similar day and night clearance rates. These results could be ex plained in relation to differences in predation risks and probability of ex periencing starvation episodes in their respective habitats, as well as the ir capacity for dampening food fluctuations. On the other hand, the mainten ance (although with less intensity) of the diel feeding rhythm in A.grani, when cultured in the laboratory for long periods of time (>10 generations) and in the absence of predators, suggests the importance of the endogenous control of copepod feeding patterns.