Behavioural and physiological responses of Gammarus fossarum (Crustacea Amphipoda) exposed to silver

Abstract

The study aims at investigating the effects of silver (Ag), a re-emerging contaminant, on physiological and behavioural responses in Gammarus fossarum. In a first experiment, G. fossarum Ag LC50s were evaluated during 96h under semi-static mode of exposure. Juveniles appeared to be more sensitive to Ag (LC5096h: 1.01μgL−1) than ovigerous females (LC5096h: 1.9μgL−1) and adult males (LC5096h: 2.2μgL−1). In a second experiment, the physiological (osmo-/ionoregulation; antioxidant enzymes; lipid peroxidation (LPO)) and behavioural (locomotor activity and ventilation) responses of male G. fossarum exposed to Ag (0, 0.5, 1, 2, and 4μgL−1) were investigated. The mortality and Ag bioconcentration of gammarids exposed to Ag were significantly higher than controls. Concerning physiological responses, a 48h-exposure to Ag had no impact on catalase activity but led to a significant decrease of haemolymph osmolality and [Na+]. On the contrary, LPO, Se-GPx and Na+/K+-ATPase activity were significantly increased. Behavioural responses, such as locomotor and ventilatory activities, were also significantly reduced in Ag exposed gammarids. After 96h-exposure, especially to 0.5μg AgL−1, most responses (ventilation, locomotor activity, haemolymph osmolality and [Na+]) were even more pronounced and haemolymph [Cl−] was significantly decreased but, contrary to observations after 48h-exposure, Na+/K+-ATPase activity was significantly reduced. Our results demonstrate the drastic effects of realistic [Ag] concentration (0.5μgAgL−1) on an ubiquitous and functionally important freshwater invertebrate (implied in detritus breakdown), but also strongly suggest an energetic reallocation to the detriment of locomotor activity and in favour of maintenance functions (i.e., osmoregulation and detoxification). These results highlight the risk represented by Ag and the need to perform integrated studies (at different scales, from individual to ecosystem).