Cost of reproduction. Changes in metabolism and endosulfan lethality caused by reproductive behavior in Hyalella curvispina (Crustacea: Amphipoda)

Abstract

Biocides are periodically applied in agricultural activities, reaching aquatic systems and acting upon the biota. Amphipods are widely used in toxicity tests because of their sensitivity to a wide range of pollutants. In this work, we report the differential lethality of a widely used pesticide, endosulfan, on the amphipod Hyalella curvispina at two life stages and in three different adult groups, males and females separated by sex and both sexes grouped together. In addition, oxygen consumption of adult groups was determined as a way to estimate the role of behavioral activities and exposure to toxic agents in metabolism shift. Juveniles were as resistant as adults separated by sex. When grouped without sexual differentiation, adults were more sensitive to toxic agents. The oxygen consumption rate was higher when adults were grouped without sexual differentiation in the control group. The exposure to low concentrations causes an increase in oxygen consumption in all the treatments. Sexual behavior could have increased metabolism and sensitivity to endosulfan. Using only juveniles or adults separated by sex in toxicity tests may inaccurately estimate the lethality of biocides, especially in species with constant reproductive activities.