EFFECT OF TOTAL ORGANIC CONTENT OF EGGS ON HATCHING SUCCESS AND NAUPLIAR SURVIVAL IN THE COPEPOD CALANUS-HELGOLANDICUS

We collected female Calanus helgolandicus weekly from 12 July to 16 August 1993 at a station southwest of Plymouth, England. We estimated the amount of food available by analyzing surface-water samples for total particulate protein, carbohydrate, and lipid in three size fractions: 0.6-100, 5-100, and 10-100 mu m. Size and the protein, carbohydrate, and lipid content of the eggs laid by these females varied with time and were positively correlated with the amount of food available. An experiment with adult female C. helgolandicus kept at six different food concentrations confirmed the field results. Hatching success and naupliar survival under starvation increased with egg size. Thus, variation in egg size is important to the population dynamics of this species.