Photoperiodic time measurement in Antarctic krill: - The effect of photoperiod on the seasonal development and the role of clock-genes -

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Antarctic krill Euphausia superba plays a central role in the Southern Ocean ecosystem, being the major trophic link between primary producers and several vertebrate top predators. Consequently, it is of vital importance to understand krill life history and biology as a key for developing self-sustaining management programmes for the krill fishery and to provide for the health of the entire Antarctic marine ecosystem. That requires knowledge of its seasonal development in general, and the behavioural and physiological mechanisms that enable krill to adapt to the Antarctic environmental conditions in particular. The habitat of krill is dominated by extreme seasonal changes in food availability, sea ice extent, day length, and light intensity. However, up to now the mechanisms in regard to synchronization between the seasonal development of krill and the seasonal cycles of food, ice and light are still poorly known. Laboratory studies have shown the influence of different simulated light regimes on physiological function of krill such as feeding activity, metabolic rates and maturity for the first time. The results suggest that photoperiod and light intensity are environmental triggers controlling seasonal behavioural and physiological characteristics of krill. The major aim of the proposed project is to study the potential effect of photoperiod on the seasonal development of life-cycle parameters of Antarctic krill. For this purpose, live krill will be exposed to a laboratory simulation of an annual course of Antarctic photoperiod. In addition, molecular analyses will identify circadian clock genes in krill that may be involved in daily and/or seasonal rhythms exhibited by krill. Whether the laboratory observations can be verified in the natural environment will be proved by analysing krill from different seasons and different latitudes in the wild.