Stress responses to conspecific visual cues of predation risk in zebrafish

Abstract

Chemical communication relating to predation risk is a trait common among fish species. Prey fish under threat of predation can signal risk to conspecific fish, which then exhibit defensive responses. Fish also assess predation risk by visual cues and change their behavior accordingly. Here, we explored whether these behavioral changes act as visual alarm signals to conspecific fish that are not initially under risk. We show that shoals of zebrafish (Danio rerio) visually exposed to a predator display antipredator behaviors. In addition, these defensive maneuvers trigger antipredator reactions in conspecifics and, concomitantly, stimulate the hypothalamus-pituitary-interrenal axis, leading to cortisol increase. Thus, we conclude that zebrafish defensive behaviors act as visual alarm cues that induce antipredator and stress response in conspecific fish.

Odours of non‐predatory species help prey moderate their risk assessment

“…Indeed, most of these studies found no difference in prey responses to the ambient and no‐predatory species controls (Brooker & Dixson, ; Caine & Weldon, ; Epp & Gabor, ; Grostal & Dicke, ; Marko & Palmer, ). The studies that did find elevated defensive responses towards the non‐predator cues interpreted the results as inaccurate predator recognition, or overgeneralization of risk (Dixson, Munday, & Jones, ; Oliveira et al, ). Here too, the design seems to reflect the asymmetric presumption that cues of non‐predatory species cannot moderate fear.…”

Sensory ecology of ostariophysan alarm substances

“…These results suggest the existence of chemical cues that are released in the water by non‐injured fish (disturbance signals) to warn conspecifics of the presence of predators. Another interesting finding is that D. rerio visually exposed to a predator display antipredator behaviours, including tighter shoaling, that in turn trigger defensive behaviour in conspecifics which did not originally see the predator (Oliveira et al ., ). The relationship between cortisol and behavioural responses, however, has not yet been determined, opening an interesting avenue of investigation.…”

“…The activation of the POA that is observed after CAS exposure is possibly related to the neuroendocrine profile that is observed in CAS‐exposed animals. Increases in cortisol levels were observed after CAS (Abreu et al ., ; Mathuru et al ., ; Schirmer et al ., ; Silva et al ., ) and disturbance signals (Barcellos et al ., , ; Oliveira et al ., , ; §9) in different species. Moreover, in D. rerio CAS elevates plasma levels of norepinephrine, epinephrine and glucose (Maximino et al ., ), strongly implicating the sympathetic system in these vegetative adjustments.…”

“…CASMathuru et al, 2012;Schirmer et al, 2013;Silva et al, 2015) and disturbance signals(Barcellos et al, 2011(Barcellos et al, , 2014Oliveira et al, 2013Oliveira et al, , 2017; §9) in different species. Moreover, in D. rerio CAS elevates plasma levels of norepinephrine, epinephrine and glucose(Maximino et al, 2014), strongly implicating the sympathetic system in these vegetative adjustments.…”

Size‐dependent stress response in juvenile Arctic charr (Salvelinus alpinus) under prolonged predator conditioning

“…Previous studies demonstrate that young Arctic charr respond strongly and innately to the chemical cues of pikeperch by reducing their swimming activity and by freezing (Vilhunen & Hirvonen, 2003). As a direct measure of stress response, we measured the whole-body levels of cortisol, a key stress glucocorticoid hormone (Oliveira et al, 2017;Sapolsky, Romero, & Munck, 2006;Wendelaar Bonga, 1997). In addition, as an indirect measure of prolonged stress response and increased cortisol levels on immune defence (see Cuesta et al, 2005), we measured the relative sizes of the spleen.…”