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

7 pages, 2 figuresThe effects of food availability on the daily feeding pattern of planktonic copepods was studied for two species: Acartia grani (cultured and wild specimens) and Centropages typicus (wild specimens). Both species showed clear diel feeding rhythms at high food concentrations, with significantly higher clearance rates during night hours. However, at limiting food conditions, while C. typicus maintained its daily feeding pattern, A.grani fed continuously, with similar day and night clearance rates. These results could be explained in relation to differences in predation risks and probability of experiencing starvation episodes in their respective habitats, as well as their capacity for dampening food fluctuations. On the other hand, the maintenance (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 patternsThis work was supported by a grant from the Spanish Ministry of Research and Universities to A.C. (PN92-46651369 and EX96-46651369), a post-doctoralfellowship from the Basque Country Government to X.I., CICYT grant AMB94-0746, AMB94-0853 and the UE MAST-II grant MAS2 CT93-0063Peer Reviewe