Moult cycle and growth of Antarctic krill Euphausia superba in the laboratory

Abstract

The first moult always showed the greatest growth increment. High laboratory growth rates agreed with previous field investigations. Moulting was partly synchronous, and moult frequency was temperature dependent. Krill was very sensitive to experimental variation in feeding regime: 1) moult frequency (14-29 d) and 2) growth increment at moult (-15 to 21%) varied together. Ecdysis and the staging and timing of the moult cycle were studied. The apparent plasticity of growth parameters indicates that, in the wild, krill is able to adapt to strong regional and seasonal changes in feeding conditions, typical for Antarctic waters. Attaining a large size enables fast swimming which facilitates location of rich food sources. Favourable feeding conditions immediately initiate growth. Essentially unhindered motility during actual moult and extremely fast ecdysis were interpreted as an adaptation to a pelagic way of life. -from Author