The effect of food on the determination of sex ratio in Calanus spp.: evidence from experimental studies and field data

The effect of food concentration on the sex ratio in Calanus spp, has been investigated in laboratory and mesocosm experiments. The results of the exp eriments are compared with time series in the field and with physiological rates. The food concentration and quality had an effect on the sex ratio of adult Calanus, with higher percentages of males obtained with increased fo od concentration. Laboratory experiments and field time series suggest that sex can still change at stage CIII-CIV, but is determined at stage CV. The energy budget of males was very unbalanced, suggesting that the shorter li fespan often reported could be due to exhaustion of lipid stores.