Anxiety-like behaviour increases safety from fish predation in an amphipod crustacea

Anxiety is an emotional state generally expressed as sustained apprehension of the environment and elevated vigilance. It has been widely reported in vertebrates, and, more recently, in a few invertebrate species. However, its fitness value remains elusive. We investigated anxiety-like behaviour and its consequences in an amphipod crustacean, using electric-shock as an aversive stimuli, and pharmacological assays. Anxiety-like state induced by electric shocks in Gammarus fossarum was expressed through increased sheltering behaviour in absence of predation risk, thereby showing the pervasive nature of such behavioural response. Increasing the number of electric shocks both increased refuge use and delayed behavioural recovery. The behavioural effect of electric shock was mitigated by pre-treatment with LY354740, a metabotropic glutamate receptor group II/III agonist. Importantly, we found that this modulation of decision making under anxiety-like state resulted in an increased survival t...