Combined effects of abamectin and temperature on the physiology and behavior of male lizards (Eremias argus): Clarifying adaptation and maladaptation.

Abstract

Chemical pollution and global warming are two major threats to organisms, which can interact to affect the normal activities of living beings. In this study, to explore the effects of abamectin and high temperature on adaptability of lizard, male adult Eremias argus (a native Chinese lizard) were exposed to environmentally relevant concentrations of abamectin (0.02 mg·L-1 and 2 mg·L-1) and different temperature (26 °C and 32 °C) for 30 days. The fitness-related behaviors (locomotion, predation, and thermoregulation) of lizards were evaluated. Physiological effects were addressed using biochemical biomarkers related to oxidative stress, detoxification, and neurotransmitter content. The results showed that abamectin could affect the neurotransmitter systems, cause oxidative stress, and alters lizard locomotion and predation-related behaviors of lizards, but lizards up-regulating detoxification metabolic enzymes, exhibiting higher body temperature preference to alleviate the toxicity of abamectin, and compensate the increased energy demand for detoxification and repair damage by increasing food intake. After exposure to high temperature, lizards showed adaptation to high temperature (higher body temperature preference), the thermal compensation mechanisms may involve elevated Hsp70 levels and increased food intake. At the combined effects of abamectin and high temperature, more obvious behavioral disorders and more severe oxidative stress were observed, although lizards avoided the negative effects of overheating and pollutants by seeking thermal shelter and reducing energy expenditure, this may subsequently reduce foraging opportunities and the ability to obtain energy needed for vital physiological functions (i.e., growth, maintenance, and reproduction). From a long-term perspective, these short-term adaptive strategies will be detrimental to individual long-term survival and population sustainability, and may transformed into maladaptation.