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Species of Diptera (larval Culicidae, Chironomidae and Simuliidae) and Crustacea (cladoceran adults) that are representative of the fauna of aquatic alpine ecosystems are routinely treated with Bacillus thuringiensis var. israelensis (Bti) for mosquito control. The toxicity of Bti on these organisms was investigated. Bioassays indicated that Bti used at the concentration for operational field application is deleterious to all dipteran species, but not to Cladocera. Histopathological observations reveal that, in all cases, the midgut epithelium is affected by Bti treatment. However, the vulnerability of epithelial cells to the microbial insecticide is different from one cell‐type to another, clear cells being more vulnerable than dark cells. Because of the concentration of clear cells within the anterior midgut of dipteran larvae, this region appears to be the first to show symptoms of intoxication through enhancing a natural process of cell turnover. The relative importance of such a vulnerable region in the midgut of dipteran larvae may account for the general efficacy of Bti to these species. Its harmlessness to Cladocera may be correlated to the relative scarcity of clear cells and their patchy distribution along the whole midgut together with important cellular renewal capacity of the epithelium.

As an example of the relative impact of a specific ambient parameter on intraspecific phenotypic differentiation, the contribution of environmental sources of calcium on the geographic variation between alpine populations of the freshwater crustacean Gammarus fossarum was investigated through a comparative analysis of six different populations in the torrents of the Grenoble region of France.Major differences in water calcium levels were observed in correlation with lithological differences (average 13.6 mg/L in the crystalline massif of the Belledonne and 83.4 mg/L in the limestone areas of the Chartreuse and Vercors). The comparative analysis of the populations was performed through field and laboratory experimentation at morphometrical and ecophysiological levels. Uniform samples of male adult specimens from six different sites (two sites in the Belledonne, two sites in the Chartreuse, and two sites in the Vercors) were compared using three easily measurable parameters: maximum dry mass, duration of the molt cycle, and calcium balance during the molt cycle.Animals from waters that flow over limestone show a larger maximum size and a longer molt cycle than those from waters that flow over crystalline rocks. Spectrophotometrical analysis of their calcium balance during the molt cycle reveals that, whereas all animals are equally calcified during the intermolt, the decalcification during the premolt and the recalcification during the postmolt are more rapid in animals from limestone areas than in those from crystalline sites. Translocation experiments in both natural and artificially calcium-enriched waters confirm these differences. A significant increase in the duration of the molt cycle was observed in animals translocated to water of lower calcium concentration and vice versa, whereas no significant difference was observed between controls and animals translocated into water of comparable calcium concentration. Current results, supported by such a new synthetic experimental approach, indicate that variations in water calcium levels may generate important ecophysiological differentiation between populations, which may suggest a possible influence of environmental calcium on the geographic distribution of Gammarus fossarum.

In order to examine the usefulness of detoxifying genes as molecular markers in different chemical environments, isolation of cytochrome P450 genes (CYPs) belonging to the CYP4 family was performed in different samples from two subalpine populations of Daphnia pulex. The use of degenerate primers allowed us to isolate seven cDNAs. Four of them were assigned to the CYP4C subfamily, and were closely related to previously isolated crustacean CYP4s while the others were assigned to new CYP4AN and CYP4AP subfamilies. Expression studies, using semiquantitative polymerase chain reaction (PCR) followed by Southern blot hybridization with specific probes revealed differences in CYP4C32 and CYP4AP1 expressions between the two populations, which differ in the polyphenol richness of the vegetation surrounding their aquatic habitat. Further exposure to toxic dietary polyphenols showed different CYP induction patterns. Taken together, these preliminary results suggest a possible involvement of CYP4s in the ecological differentiation of subalpine D. pulex populations related to the polyphenol richness of the environmental vegetation. CYP4s may thus be considered as possible molecular markers in aquatic environmental bioreporting.