Cortisol mediates cleaner wrasse switch from cooperation to cheating and tactical deception

Abstract

Recent empirical research, mostly done on humans, recognizes that individuals" physiological state affects levels of cooperation. An individual"s internal state may affect the payoffs of behavioural alternatives, which in turn could influence the decision to either cooperate or to defect. However, little is known about the physiology underlying condition dependent cooperation. Here, we demonstrate that shifts in cortisol levels affect levels of cooperation in wild cleaner wrasse Labroides dimidiatus. These cleaners cooperate by removing ectoparasites from visiting "client" reef fishes but prefer to eat client mucus, which constitutes cheating. We exogenously administrated one of three different compounds to adults: a) cortisol, b) glucocorticoid receptor antagonist mifepristone RU486 or c) sham (saline); and observed their cleaning behaviour during the following 45 min. The effects of cortisol match an earlier observational study that first described the existence of "cheating" cleaners: such cleaners provide small clients with more tactile stimulation with their pectoral and pelvic fins, a behaviour that attracts larger clients that are then bitten to obtain mucus. Blocking glucocorticoid receptors led to more tactile stimulation to large clients. As energy demands and associated cortisol concentration level shifts affect cleaner wrasse behavioural patterns, cortisol potentially offers a general mechanism for condition dependent cooperation in vertebrates.

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

“…In the obligate cleaner L dimidiatus, an increase in AVT levels, induced with exogenous peripheral infusions, caused them to cease all mutualistic activities, but not conspecific behaviour (Soares et al, 2012a(Soares et al, , 2012c. These results contrast with those found with cortisol treatments, with cleaners altering strategic tactics towards their clientele (see section 5.1 above, and Soares et al (2014) and Binning et al (2017)). Thus, different stress response magnitudes, appear to produce significant behavioural responses.…”

“…These mechanisms have been further to propitiate cleaners behavioural switch from cooperation to cheating (Soares et al, 2014). Specifically, cleaners behavioural change occurs under influence of rising cortisol levels, with these providing more tactile stimulation to smaller clients as to gain access to bigger ones, that are then bitten (Soares et al, 2014).…”

“…These mechanisms have been further to propitiate cleaners behavioural switch from cooperation to cheating (Soares et al, 2014). Specifically, cleaners behavioural change occurs under influence of rising cortisol levels, with these providing more tactile stimulation to smaller clients as to gain access to bigger ones, that are then bitten (Soares et al, 2014). And also, mediated by the antagonism of the glucocorticoid receptors, which produced a positive improvement of cleaning service (more tactile stimulation to bigger clients, those that have more ectoparasites and more mucus), and thus contributing to a reinforcement of current and future relationships (Soares et al, 2014).…”

Associations between glucocorticoids and sociality across a continuum of vertebrate social behavior

“…Thus, when cooperation has only long‐term rewards, such as an increased chance of reproduction in the distant future, we predict that increased GCs are likely to reduce cooperative motivation and impair cooperative coordination. For example, after being experimentally stressed, female cleaner wrasses ( Labroides dimidiatus ) switched to a more selfish and less cooperative behavior where they bite nutritious mucus from their interspecific client fish partner (Soares, Cardoso, Grutter, Oliveira, & Bshary, 2014). This may be costly in terms of jeopardizing future partnerships with their clients, but provides more proximate benefits.…”

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).…”