Locomotor activity rhythms in high arctic freshwater crustacean: Lepidurus arcticus (Branchiopoda; Notostraca)

The overall aim of this project is to characterize circadian organization in a polar invertebrate the tadpole shrimp, Lepidurus arcticus. No work on the circadian biology of this fascinating group has been published, and their behavioral rhythmicity in the high arctic is of great interest from an eco-evolutionary perspective. Although the existence 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 (e.g. caves, the deep sea and the polar regions) has received very little attention. This branch of the field is of particular importance because it places the adaptive value of circadian timing in proper evolutionary perspective. Work in reindeer by K. Stokkan and coll. (Nature, 2005; Cur. Biol., 2010) suggests that circadian clocks may be weakened as part of the adaption to exploit continuous illumination in the polar summer, but studies on 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 a. 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 different latitude in Norway. Hence it will possible to develop a latitudinal comparison of both behavior and genetic aspects, and (beyond the scope of this proposal) crossing experiments to assess heritability of circadian traits can also be envisaged. A preliminary experiment has been conducted during the month of August 2014 on Svalbard in CNR Italian Arctic Statin "Dirigibile Italia". This first study on the behavioral analysis of the locomotor activity rhythms in Lepidurus a. certainly deserves further investigation. The data presented here emphasizes that L. arcticus, recorded individually and in groups in natural condition during the arctic summer, do not show circadian rhythm.