Melatonin and polar lighting effects on an arctic living fossil (Lepidurus arcticus) RIS-ID 10011

The overall aim of this project is to characterise circadian organisation in a polar invertebrate Lepidurus arcticus. Although the existience of circadian clocks is accepted as ubiquitous feature of life, and their physiological mechanisms are becoming well understood, the role of circadian clocks in extreme environments has received very little attention. Circadian clocks may be weakened as part of the adaption to exploit continuous illumination in the polar summer, but studie sin birds and ground squirrels suggest that depending on ecological context circadian rhythms may be maintained. No data on this topic have been gathered from a high arctic invertebrate. Lepidurus is the ideal model in which to develop this aspect because of its presence in melt-water pools in Svalbard, and because conspecifics can also be found at altitude in mainland sites around Tromsø. Hence it will possible to develop a latitudinal comparison of both behaviour and genetic aspects, and crossing experiments to assess heritability of circadian traits can also be envisaged. Our first objective is to retrun to Svalbard in order to explore rhythmicity in Lepidurus and to compare this rhythmiciy under a field-laboratory imposed light dark cycle. This will allow us to determine whether bahaviour is under circadian control, and if so whether this continues under constant illumination. Our second objective is to determine whether Lepidurus expresses homologues of ?clock genes? known to govern circadian biology in modern arthropods and in vertebrates. Our thrid major objective is to investigate the possible role of melatonin in seasonal and circadian biology in Lepidurus. We will therefore investigate melatonin effects in our behavioural assay, collect samples for assay of melatonin levels in Lepidurus, and explore our transcriptomic data to determine whether genes for the key enzymes controlling melatonin synthesis may be present in this ancient lineage.