Modification de la sensibilité au lindane d'Asellus aquaticus L. en fonction de la variation de facteurs biotiques (poids et métabolisme) et abiotiques (concentration de l'insecticide et température) Sensitivity of Asellus aquaticus L. (Crustacea, Isopoda) to lindane in relation to biotic (size and metabolism) and abiotic factors (concentration of insecticide and temperature)

Résumé

La sensibilité d'Asellus aquaticus L. (Crustacea, Isopada) à un insecticide, le lindane, est étudiée. Pour chaque concentration de lindane (1, 2, 4 et 8 mg.L^-1) la mortalité est appréciée en fonction du poids des individus ou de leur métabolisme. La sensibilité à 4 mg.L^-1 de lindane à des températures différentes (10 et 20 °C) a été également envisagée. La sensibilité des aselles s'accroit avec la concentration de lindane, la température et le métabolisme. Il en est de même aux concentrations sublétales quand le poids augmente.

Mots-clés:

• Asellus aquaticus,
• lindane,
• sensibilité,
• écophase

Abstract

The sensitivity of Asellus aquaticus L. (Crustacea, Isoposa) to the insecticide lindane was studied in relation to its developmental stage (size) and metabolism. After tests of acute toxicity (48 h) with 1, 2, 4 or 8 mg.L^-1 of lindane, the percentage of mortality increased with the concentration. In further tests using sublethal concentrations, 1 or 2 mg.L^-1, the sensitivity increased with the weight of the organisms. A linear regression of mortality (probit of %) of Asellus was correlated with the mean concentration (M) of lindane and the weight (W) of Asellus for these two concentrations. It is possible to relate the percentage of mortality to the metaboilc rate observed at the beginning of the experiment. The larger Asellus and/or those with a higher metabolic rate were the most sensitive. An increase in temperature which modified the metabolism, increased the sensitivity of this invertebrate. The percentage of mortality were respectively 1.35 and 26.64 at 10 and 20 °C. The interest of these results lies in the evaluation of the risks of pollution. In this type of study, it is very important to consider the biotic factors (size, metabolism) because the concentration of insecticide is generally close to a sublethal concentrations. Indeed biotic factors that modify the sensitivity are the main elements responsible for the intensity of the harm caused. The abiotic factor (temperature) that changes the physiology of invertebrate is also a significant factor.

Keywords:

• Asellus aquaticus,
• lindane,
• sensitivity,
• developmental stage