Face Your Fears: Cleaning Gobies Inspect Predators despite Being Stressed by Them

Abstract

Social stressors typically elicit two distinct behavioural responses in vertebrates: an active response (i.e., “fight or flight”) or behavioural inhibition (i.e., freezing). Here, we report an interesting exception to this dichotomy in a Caribbean cleaner fish, which interacts with a wide variety of reef fish clients, including predatory species. Cleaning gobies appraise predatory clients as potential threat and become stressed in their presence, as evidenced by their higher cortisol levels when exposed to predatory rather than to non-predatory clients. Nevertheless, cleaning gobies neither flee nor freeze in response to dangerous clients but instead approach predators faster (both in captivity and in the wild), and interact longer with these clients than with non-predatory clients (in the wild). We hypothesise that cleaners interrupt the potentially harmful physiological consequences elicited by predatory clients by becoming increasingly proactive and by reducing the time elapsed between client approach and the start of the interaction process. The activation of a stress response may therefore also be responsible for the longer cleaning service provided by these cleaners to predatory clients in the wild. Future experimental studies may reveal similar patterns in other social vertebrate species when, for instance, individuals approach an opponent for reconciliation after a conflict.

The Integration of Sociality, Monoamines, and Stress Neuroendocrinology in Fish Models: Applications in the Neurosciences

“…This raised questions regarding cleaners' appraisal of fear, or if these fish could be suffering from a kind of "heterospecific boldness syndrome (HBS)" which would enable them to happily deal with dangerous clients. This hypothesis (HBS) was later refuted, as cleaners were found to respond with higher cortisol levels when exposed (visually) to piscivores compared to other harmless clients (Soares et al, 2012b). The authors interpreted cleaners' proactivity towards these clients, that rapidly approached predators and reduced the time elapsed between client approach and the start of the interaction process, as a way to interrupt the potentially harm of the physiological consequences elicited by predatory clients and to secure a safe outcome to these interactions (Soares et al, 2012b).…”

“…We decided to extend the tests done by Soares et al (2012b) to E. prochilos, wondering if cortisol response mechanisms could be related to the increase in socio-ecological challenges seen in this species (for methodology, please see Soares et al (2012)). Thus, specimens from both species were collected in similar habitats (coral heads) and all were identified as cleaners (aka, none of the gobies were collected in sponges).…”

“…evelynae individuals, cortisol immunoreactivity in holding water varied significantly over time and in interaction between treatment and time (for methods and results Soares et al (2012b) but also the caption of Figure 2). On the other hand, E. prochilos individuals had a significantly wider physiological range regarding cortisol secretion (Figure 2).…”

The Integration of Sociality, Monoamines, and Stress Neuroendocrinology in Fish Models: Applications in the Neurosciences

“…This hypothesis was later refuted, as cleaners were found to respond with higher cortisol levels when exposed (visually) to piscivorous compared to other harmless clients (Soares et al, 2012b). Furthermore, authors interpreted cleaners' proactivity towards these clients, by rapidly approaching predators, both in captivity and in the wild, and by reducing the time elapsed between client approach and the start of the interaction process, as a way would interrupt the potentially harm of the physiological consequences elicited by predatory clients, securing a safe outcome to these interactions (Soares et al, 2012b) that interactions following those involving predators, are increasingly more cooperative Gingins et al, 2013), which pointed for a deeper role of stress mechanisms into the shortterm modulation of cleaners' cooperative levels. These mechanisms were further investigated in natural conditions, when the exogenous effects of cortisol were found to propitiate cleaners behavioural switch from cooperation to cheating (Soares et al, 2014).…”

Erratum to: When good advertisement backfires: cleaners get eaten too

“…This methodology has been extensively applied before, without a similar occurrence ever being reported (Soares et al 2012(Soares et al , 2014Paula et al 2015).…”