Mechanisms underlying the control of responses to predator odours in aquatic prey

Abstract

In aquatic systems, chemical cues are a major source of information through which animals are able to assess the current state of their environment to gain information about local predation risk. Prey use chemicals released by predators (including cues from a predator's diet) and other prey (such as alarm cues and disturbance cues) to mediate a range of behavioural, morphological and life-history antipredator defences. Despite the wealth of knowledge on the ecology of antipredator defences, we know surprisingly little about the physiological mechanisms that control the expression of these defensive traits. Here, we summarise the current literature on the mechanisms known to specifically mediate responses to predator odours, including dietary cues. Interestingly, these studies suggest that independent pathways may control predator-specific responses, highlighting the need for greater focus on predator-derived cues when looking at the mechanistic control of responses. Thus, we urge researchers to tease apart the effects of predator-specific cues (i.e. chemicals representing a predator's identity) from those of dietmediated cues (i.e. chemicals released from a predator's diet), which are known to mediate different ecological endpoints. Finally, we suggest some key areas of research that would greatly benefit from a more mechanistic approach.

Knowing the Enemy: Inducible Defences in Freshwater Zooplankton

“…Cues generated through feeding on conspecifics seem to exert stronger responses than cues derived from feeding on other prey species, or from a Daphnia-free diet [22]. Thus, Mitchell et al [237] proposed a distinction between predator cues that are directly originating from the predator itself, dietary cues that are a result or a by-product of the digestion process of the predator, and alarm cues originating from injured prey. These different classes of cues are often difficult to separate experimentally.…”

Microplastic leachates impair behavioural vigilance and predator avoidance in a temperate intertidal gastropod

“…So far, no evidence exists on the potential effect of plastic pellet leachate on predator -prey interactions, in particular on the ability of prey to detect and avoid its predator. These species-specific behaviours are typically mediated by chemical cues [14], whose detection is compromised by chemical pollution [15]. This study assessed experimentally whether prey vigilance and…”

No trade‐offs in interspecific interference ability and predation susceptibility in newt larvae

“…Previous studies demonstrated that dragonfly larvae are important predators of newt larvae in our study population (Gvoždík & Smolinský, 2015;Smolinský & Gvoždík, 2013). To provide newt larvae with both predator odor and diet cues (Mitchell, Bairos-Novak, & Ferrari, 2017), we fed dragonfly larvae with two living newt larvae at 4-day intervals. The species composition of dragonfly prey was chosen according to species composition and density of newt larvae in a given tank, that is, only I. alpestris, only L. vulgaris, and mixed I. alpestris-L. vulgaris diet.…”