We investigated the potential variability of enzymatic antioxidant activities in blue mussels Mytilus edulis from a single intertidal population but living at different tidal heights. Activity levels of antioxidant enzymes (Cu/Zn superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione transferase) were measured in the gills and digestive gland of mussels sampled at high shore (HS, air-exposure>6h/12h) and low shore (LS, air-exposure<2h/12h) of an intertidal zone (Yport, Normandie, France) for two consecutive autumns. In both tissues, levels of each enzymatic activity (except GST) were clearly higher in HS mussels than in LS for the two years. These results suggest an ability to acclimate the enzymatic antioxidant defences to the degree of undergone stress, confirming the importance of environmental conditions in the antioxidant responses. Therefore, the location of organisms on the shore should be taken into account in sampling for ecotoxicological studies.

The extent of damage to crop plants from pest insects depends on the foraging behaviour of the insect's feeding stage. Little is known, however, about the genetic and molecular bases of foraging behaviour in phytophagous pest insects. The foraging gene (for), a candidate gene encoding a PKG-I, has an evolutionarily conserved function in feeding strategies. Until now, for had never been studied in Lepidoptera, which includes major pest species. The cereal stem borer Sesamia nonagrioides is therefore a relevant species within this order with which to study conservation of and polymorphism in the for gene, and its role in foraging -a behavioural trait that is directly associated with plant injuries. Full sequencing of for cDNA in S. nonagrioides revealed a high degree of conservation with other insect taxa. Activation of PKG by a cGMP analogue increased larval foraging activity, measured by how frequently larvae moved between food patches in an actimeter. We found one non-synonymous allelic variation in a natural population that defined two allelic variants. These variants presented significantly different levels of foraging activity, and the behaviour was positively correlated to gene expression levels. Our results show that for gene function is conserved in this species of Lepidoptera, and describe an original case of a single nucleotide polymorphism associated with foraging behaviour variation in a pest insect. By illustrating how variation in this single gene can predict phenotype, this work opens new perspectives into the evolutionary context of insect adaptation to plants, as well as pest management.

The molecular characterization of post-receptor actors involved in insect olfactory transduction has yet to be understood. We have investigated the presence of a Transient Receptor Potential (TRP) channel in the peripheral olfactory system of the moth Spodoptera littoralis. A cDNA encoding a Lepidopteran TRP channel (TRPgamma) was identified by analysis of a male-antennal EST database and subsequently cloned by RACE PCR. In adult males, the TRPgamma transcript was detected in antennae, at the base of olfactory sensilla. Moreover, TRPgamma was observed in antennae in both pupal and adult stages. This work is the first step in understanding the involvement of TRPgamma in signalling pathways involved in the development and function of the insect olfactory system.