Egg-production dynamics, biochemical composition and hatching success of the subantarctic copepod Paraeuchaeta antarctica:: laboratory studies

The reproductive time scale, protein, and lipid contents of eggs and egg hatching success of the predatory calanoid copepod Paraeuchaeta antarctica from the Kerguelen Archipelago was investigated during the winter peak of reproduction, using females in captivity. The mean time taken by females to produce egg sacs was 21.5 d after the appearance of developing eggs in the oviducts. On average, eggs hatched 23.7 d after deposition of the sac, at 2 degreesC. After hatching, females took an average of 9.6 d to produce a second egg sac. These periods did not vary as a function of collection date (August and September) or time in captivity. Egg mortality within the sac averaged 8%, but strongly increased with increased time in captivity. Captivity also induced a strong decrease in maternal lipid and protein contents and in the number of eggs per sac. However, the lipid content of eggs remained constant and the protein content decreased with increasing brood size. This indicated that P. antarctica were limited by available protein rather than lipid. The biochemical composition of the eggs did not change in relation to development, although egg diameter varied from 381 mum at egg deposition to 448 pm after 15 d development. Some females were fed with small copepods. Prey clearance and effect of concentration of prey on the female protein content indicated that predatory feeding occurs during winter in P. antarctica from Kerguelen. The estimation of the fecundity of P. antarctica females led to a production of 175.2 eggs female(-1) yr(-1), 91% of which took place between July and December. From June to October, winter production of eggs relied equally on maternal reserves accumulated during the summer and on carnivorous feeding at low prey concentrations.