1. Respiratory electron transport system (ETS) activity and oxygen consumption were measured at 10°C for the hypogean amphipods Niphargus stygius (from two epikarst locations) and N. krameri (from a sinking river in a cave) and the epigean amphipod Gammarus fossarum (inhabiting a spring and a river). 2. ETS activity and oxygen consumption were compared between caves and the two surface locations, and between hypogean and epigean amphipods. ETS activities were found not to differ between animals from different locations, or between epigean and hypogean amphipods. As expected, the oxygen consumption of N. krameri and N. stygius was lower than that of G. fossarum. 3. The high ratio between ETS activity and oxygen consumption (ETS/R ratio) showed that N. krameri and N. stygius possess high metabolic potential that can be exploited for energy recovery and rapid restoration of body reserves immediately following the appearance of favourable conditions (food and/or oxygen). In contrast, G. fossarum exhibited a low ETS/ R ratio, indicating exploitation of a great proportion of the metabolic potential for standard metabolism. 4. Feeding in N. stygius increased oxygen consumption but not ETS activity, and thus fed N. stygius had a much lower ETS/R ratio than starved ones. 5. A relatively high metabolic potential (i.e. high ETS/R ratio) may be an adaptation to hypogean life in amphipods, in that it improves survival under poor food and/or oxygen conditions.

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A reliable method is needed for assessing the condition of aquatic animals and their resistance to toxic pollutants. The physiological responses of two freshwater crustaceans, Asellus aquaticus and Gammarus fossarum, following in vitro exposure to two pesticides (atrazine and imidacloprid), were measured by a combination of electron transport system (ETS) activity and respiration (R). Short-term exposure concentrations were selected according to standard toxicity tests and ranged from 0.01 mg L(-1) to 10 mg L(-1). When pesticide concentration was greater than 1 mg l(- 1) (which is below the LC(50) [48 hours] determined for both species), A. aquaticus and G. fossarum responded to short-term exposure with elevated levels of R and/or lower levels of ETS activity. One hour exposure to concentrations of up to 10 mg L(-1) showed an effect in both test species. Laboratory tests confirmed that G. fossarum is more sensitive to short-term pesticide exposure than A. aquaticus. The combination of these two methods provides a useful and effective tool for assessing the general condition of aquatic animals. It also enables to determine toxic effects on freshwater biota of specific or combined pollutants. ETS/R ratio may be used as a quick predictor of effects on organisms exposed to pesticides and other stress factors such as changes in temperature, light, salinity, oxygen concentration and food.

The physiological responses of two freshwater crustaceans, Asellus aquaticus L. and Gammarus fossarum Koch., following in vitro exposure to two pesticides were measured. Both species responded to short-term exposure with elevated levels of Respiration and/or lower levels of Electron Transport System (ETS) activity. 1 h exposure to concentrations of up to 10 mg L(-1) showed an effect in both test species. Laboratory tests confirmed that G. fossarum is more sensitive to short-term pesticide exposure than A. aquaticus. ETS/R ratio may be used as a quick predictor of effects on organisms exposed to pesticides.

We investigated the effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community, together with changes in the hyporheic geomorphology, physicochemistry and biofilm activity. Hyporheic invertebrates were collected, together with environmental data, on seven sampling occasions from June 2004 to May 2005, at two river reaches-at the site of instream gravel extraction and at a site 2.5 km upstream. The hyporheic samples were taken from the river bed and from the gravel bars extending laterally from the stream channel. The invertebrate community was dominated by insect larvae (occasional hyporheos), followed by meiofauna (permanent hyporheos). Stygobionts were present at low species richness and in low densities. Gravel extraction from the stream channel led to changes in the patterns of water exchange between surface and subsurface and changes in the sediment composition at the site. Immediate reductions in density and taxonomic richness of invertebrates were observed, together with changes in their community composition. The hyporheic invertebrate community in the river recovered relatively fast (in 2.5 months) by means of density and taxonomic richness, while by means of community composition invertebrates needed 5-7 months to recover. The impact of fine sediments (\0.1 mm) on biofilm activity measured through ETS activity and hyporheic invertebrate density and taxonomic richness was strongly confirmed in this study.