Abstract
Light regime is an important zeitgeber for Antarctic krill (Euphausia superba Dana, 1850), 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 responses 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 2-year laboratory experiment simulating the latitudinal light regimes at 52°S and 66°S and constant darkness under constant food level. Our results showed that light regime affected seasonal cycles of growth, feeding, lipid metabolism, and maturity in Antarctic krill. Seasonal patterns of growth, feeding, and maturity persisted under constant darkness, indicating the presence of an endogenous timing system. The maturity cycle showed differences in critical photoperiods according to the simulated latitudinal light regime. This suggests a flexible endogenous timing mechanism in Antarctic krill, which may determine its response to future environmental changes.
Highlights
Concerns are growing about the impact of global warming on the Antarctic marine ecosystem
This study aims to investigate the effect of different light regimes on growth, feeding, lipid metabolism, and maturity in Antarctic krill, as well as the involvement of an endogenous timing system in the modulation of seasonal rhythms
The generalized additive mixed model (GAMM) revealed significant seasonal and interannual patterns in growth, which were similar across all treatments (Figs. 3a, 3b)
Summary
Concerns are growing about the impact of global warming on the Antarctic marine ecosystem. To be able to predict future changes, we need to better understand the adaptive potential of polar key organisms such as the Antarctic krill (Euphausia superba Dana, 1850) (Meyer 2010). Antarctic krill’s success in the Southern Ocean likely originates from its ability to synchronize its life cycle to local photoperiod and food supply. It has evolved seasonal patterns of growth, lipid turnover, metabolic activity (Meyer et al 2010), and maturation (Kawaguchi et al 2007) that bring an evolutionary advantage to Received 13 December 2017.
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