SEASONAL COMPARISON OF CALANOIDES-ACUTUS AND CALANUS-PROPINQUUS (COPEPODA, CALANOIDA) IN THE SOUTHEASTERN WEDDELL SEA, ANTARCTICA

The herbivorous Antarctic copepods Calanoides acutus and Calanus propinquus were studied for seasonal differences in life cycles in the southeastern Weddell Sea in January/February 1985 and in October/November 1986. During late winter/early spring older stages of C. acutus were concentrated below 500 m. Males had reduced mouthparts and were only found in October/November in deep waters where mating occurred. Females with semiripe and ripe gonads migrated to the surface in November to spawn. Their ascent coincided with an increase in swimming and respiration activity. In summer the majority of C. acutus occurred above 200 m and the density increased dramatically as the new cohort hatched. Copepodite stage CV and females in the surface layers had large lipid depots by the end of January, mainly wax esters. They seem to start their descent by mid February. C. propinquus also occurred in deeper waters in late winter/early spring, but above 500 m. Males had well-developed mouthparts and were found in small numbers throughout both investigated periods. No great changes in activity were observed from late winter to summer. The summer population was concentrated in the upper 100 m. As for C. acutus there was a dramatic increase in abundance of C. propinquus from January to February. The lipid content of CV stages and females doubled from January to February and reached similar maximum values at least 3 wk later in the season than C. acutus. The lipids of C. propinquus consisted mainly of triacylglycerol, a very unusual storage lipid class in polar calanoid copepods. C. acutus and C. propinquus seem to represent different life histories: the wax-ester-accumulating C. acutus overwinters in a resting stage in deeper waters while the triacylglycerol-storing C. propinquus may feed and reproduce over a more extended period than C. acutus.