Egg production ofCalanus finmarchicus at low temperature

Abstract

Reproduction ofCalanus finmarchicus Gunnerus collected in June 1988 in Polar water and in April 1989 in Atlantic water was studied. Single females were kept at 0°C in the laboratory for 22 d (Polar) and 77 d (Atlantic) with superabundant food concentration (> 400µg Cl⁻¹) of the diatomThalassiosira antarctica. There was no significant difference between the two populations, although more spent females were found in Polar water, probably due to the different dates of collection. The hypothesis of low temperature determining the geographic range ofC. finmarchicus via reproductive failure is not supported. Mean daily egg production rate of all females from Atlantic water over a 60 d period was 24.4, corresponding to 5.5% body C female⁻¹ d⁻¹, when an egg carbon content of 0.23µg is assumed. Coefficient of variation was 25%. Maximum values were 53.2 eggs female⁻¹ d⁻¹, corresponding to 12.1% body C d⁻¹. The highest number of eggs spawned by a single female was 3101, corresponding to a seven-fold turnover of body C during the investigation period; >20% of females produced > 2000 eggs. Body carbon content did not change significantly during the experiment; the C:N ratio increased slightly, indicating lipid accumulation. Delay of response to starvation periods of 2, 4 and 7 d duration was always 2 d: egg production ceased 2 d after the onset of starvation and continued 2 d after onset of feeding.