Egg production of the Arctic copepod Calanus glacialis: laboratory experiments

Abstract

Egg production of single female Calanus glacialis Jaschnov fed with Thalassiosira antarctica at super-abundant concentrations (>300 μg C l^-1) was determined over several weeks. Experiments were performed directly after collection from the East Greeland Current in June 1987 and 1988, and during resumed feeding after long-term starvation over 4 (October 1988), 4.5 (October 1987) and 6.5 (January 1988) mo. In addition, in June 1987, short-term starvation experiments of 5 and 15 d were conducted. Egg production was closely related to feeding in all experiments. While directly after collection eggs were produced within a few days, it took 2 wk (October 1987 and 1988) and 10 d (January 1988), respectively, to resume egg production after long-term starvation. During long-term starvation periods eggs were not laid. The decrease in total egg production with duration of starvation was due to decreasing clutch size and increasing spawning interval. In contrast, short-term starvation experiments only affected spawning interval. Interannual variability in egg production was high, with much higher clutch sizes in 1988. Average production rates in June 1988 correponded to 5% body C female^-1 d^-1, the maximum was 7.4% (1 274 eggs in 23 d). Carbon content of eggs was 0.40 μg egg^-1. C. glacialis is well adapted to pulsed food events in the Arctic by its longevity; its ability to preserve its reproductive potential over several months; its rapid mobilization of ovaries; and by its high egg production rates. The implication of prolonged spawning capacity on life cycle studies is discussed.