Light regime is an important Zeitgeber for Antarctic krill (Euphausia superba), which seems to entrain an endogenous timing system that synchronizes its life cycle to the extreme light conditions in the Southern Ocean. To understand the flexibility of Antarctic krill's seasonal cycle, we investigated its physiological and behavioural response to different light regimes and if an endogenous timing system was involved in the regulation of these seasonal processes. We analysed growth, feeding, lipid content and maturity in a two-year lab experiment simulating the latitudinal light regimes 52°S, 66°S and constant darkness under constant food level. Our results showed that light regime affected seasonal cycles of growth, lipid metabolism and maturity in Antarctic krill. Seasonal patterns of growth and maturity persisted under constant darkness indicating the presence of an endogenous timing system. The maturity cycle showed differences in development and critical photoperiods according to the simulated light regime. This suggests a flexible endogenous timing mechanism in Antarctic krill, which may determine its response to future environmental changes.

The maturity stage of the sampled krill was assessed according to Makarov and Denys (1980) and Thomas and Ikeda (1987) analysing the pictures of the external sexual organs. A maturity score was assigned using the method by Brown et al. (2010, 2011).

Supplement to: Höring, Flavia; Teschke, Mathias; Suberg, Lavinia; Kawaguchi, So; Meyer, Bettina (2018): Light regime affects the seasonal cycle of Antarctic krill (Euphausia superba): impacts on growth, feeding, lipid metabolism, and maturity. Canadian Journal of Zoology-Revue Canadienne de Zoologie, 96(11), 1203-1213