MOLT IN RELATION TO SOME ASPECTS OF REPRODUCTION AND GROWTH IN SWARMSOF ANTARCTIC KRILL, EUPHAUSIA-SUPERBA

In a 14-d period 38 swarms of Antarctic krill, Euphausia superba Dana, were sampled in an area 55.5 x 55.5 km to the southwest of Elephant I sland, at the north of the South Shetland Islands. Moult stage, maturi ty stage, and size of ca. 100 krill from each swarm were measured. Eac h of the characteristics varied greatly between swarms. Moulting krill were found in most swarms, but in one swarm all of the krill were jus t about to moult. Ways in which moulting may act as a possible sorting mechanism are discussed. Data for all the analysed krill (ca. 3000 sp ecimens) were used to investigate the interdependence of moult rate, s exual maturation and growth. While all immature krill moulted at appro ximately the same rate in the study, there were significant difference s in the moulting rates of mature male and female krill. Gravid female krill continued to moult, although less frequently than mature males. As a con sequence males had to attach spermatophores to females after each moult. It is likely that variation in moult rate of females and males was related to the energy expenditure required for ovary develop ment in females and spermatophore production and searching behaviour i n males. Spawning and moulting were only partly coupled in gravid fema les. Spawning appeared to take place predominantly during Moult Stage D-2. There was no evidence of intermoult growth by intersegmental dila tion.