Multi-generation cultivation of the copepod Calanus helgolandicus in a re-circulating system

We tested the amenability of the calanoid copepod Calanus helgolandicus to be mass cultivated in a large volume system. The copepod was reared on two different occasions (during 2009 and 2010), for at least four generations and six months with a mixed flagellate diet of Isochlysis galbana, Rhodomonas baltica and Prorocentrum minimum, or a mixed diet of I. galbana, R. baltica and the diatom Thalassiosira weissflogii. The generation time of C. helgolandicus from nauplius to adult was 21 days, with relative duration of naupliar and copepodid phases of 7 and 14 days, respectively. Population growth rates when the second generation of adults developed and reproduced in the tank, were similar to 2-times higher (0.067 d(-1) vs. 0.038 d(-1)) and abundances increased 6-times more (40-fold vs. 6.7-fold) during 2010 than 2009. This higher production was related to the addition of T. weissflogii to the mixed R. baltica +I. galbana diet at low concentrations (0.17 mg Cl-1) and for short periods (<2 months), which induced higher egg production rate and percentage of spawning females and lower copepodid mortality in the population. However, supplementation of T. weissflogii at higher concentrations (0.40 mg Cl-1) or longer feeding times (>3 months), reduced copepod egg hatching success, and hence population growth of C. helgolandicus. In conclusion, our study shows that by using an appropriate mixed diatom assemblage for short periods, it is possible to obtain healthy individuals of all larval stages of C. helgolandicus for biological, toxicological and gene expression studies year-round. (C) 2012 Elsevier B.V. All rights reserved.