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(PM252) Influence of larval age and sex on the use of energetic biomarkers in Chironomus riparius exposed to copper.

Servia, M.J.1, 2, Heydorff, M.1, Péry, A.R.R.2, Garric, J.2, Lagadic, L.1, 1 INRA EQHC, Rennes, France2 CEMAGREF, Lyon, France

ABSTRACT- The measure of energetic reserves, mainly lipids and sugars, has been presented as a reliable indicator of the physiological condition of an individual, which may have important implications in the expression of individual performances and subsequent development of population. In fact, classical endpoints used in ecotoxicity tests such as survival, growth or reproduction have already been linked to diverse energy-related biomarkers in several species. However, few studies have considered the influence of the age and sex of the individuals on the levels of those reserves. In this work we present a methodology suitable for studying the dynamics of sugar and lipid levels in the fourth instar larvae of Chironomus riparius by using the degree of development of the imaginal discs for determining the sex and age (phase) of the larvae throughout that instar. Results point out the risk for misinterpretation of data if sex and age are not considered. As a consequence, both sex and age were take into account for investigating the effects of copper on larval development and energetic biomarkers.Copper is known to induce delays in larval development of Chironomus riparius, meaning that larvae need more time to attain a certain age. Moreover, males and females present asynchronous growth. Therefore we selected groups of larvae of the same age and sex for measuring reserves. Results will be discussed in relation to the possible existence of a link between changes in levels of reserves due to toxic instult and alterations in life cycle endpoints such as growth or reproduction.

Key words: Sugars, Energy reserve, Lipids, Larval development

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