The variable monoaminergic outcomes of cleaner fish brains when facing different social and mutualistic contexts.

The monoamines serotonin and dopamine are important neuromodulators present in the central nervous system, known to be active regulators of social behaviour in fish as in other vertebrates. Our aim was to investigate the region-specific brain monoaminergic differences arising when individual cleaners face a client (mutualistic context) compared to when they are introduced to another conspecific (conspecific context), and to understand the relevance of visual assessment compared to the impact of physical contact with any partner. We demonstrated that serotoninergic activity at the diencephalon responds mostly to the absence of physical contact with clients whereas cerebellar dopaminergic activity responds to actual cleaning engagement.

Monoaminergic levels at the forebrain and diencephalon signal for the occurrence of mutualistic and conspecific engagement in client reef fish.

Social interactions are commonly found among fish as in mammals and birds. While most animals interact socially with conspecifics some however are also frequently and repeatedly observed to interact with other species (i.e.

Estradiol shapes mutualistic behaviour of female cleaner fish (Labroides dimidiatus - Valenciennes, 1839): Potential implications of environmental disturbance.

The presence of endocrine-derived compounds in the environment occurs due to a myriad of human or industrial activity and can disrupt the endocrine system of animals, including fish. One important group of endocrine disruptors are the estrogens, such as 17-β estradiol (E, estradiol). Estrogens are gonadal steroid hormones, able to be influential even in small concentrations.

Dopamine disruption increases cleanerfish cooperative investment in novel client partners.

Social familiarization is a process of gaining knowledge that results from direct or indirect participation in social events. Cooperative exchanges are thought to be conditional upon familiarity with others. Indeed, individuals seem to prefer to engage with those that have previously interacted with them, which are more accurate predictors of reward than novel partners.

Can cleanerfish overcome temptation? A selective role for dopamine influence on cooperative-based decision making.

Evidence suggests that animals are selected to make accurate choices and prioritize goals within the constraints of a given social environment to maximize fitness. These decisions are mostly based on complex processes in which value is linked to reward and cues may carry variable incentive salience. However, the level in which the incentive elicited by a cue is able to shift individual choices should differ between individuals and neurophysiological states.

Dopamine disruption increases negotiation for cooperative interactions in a fish.

Humans and other animals use previous experiences to make behavioural decisions, balancing the probabilities of receiving rewards or punishments with alternative actions. The dopaminergic system plays a key role in this assessment: for instance, a decrease in dopamine transmission, which is signalled by the failure of an expected reward, may elicit a distinct behavioural response. Here, we tested the effect of exogenously administered dopaminergic compounds on a cooperative vertebrate's decision-making process, in a natural setting.

Stimulation of dopamine D₁ receptor improves learning capacity in cooperating cleaner fish.

Accurate contextual decision-making strategies are important in social environments. Specific areas in the brain are tasked to process these complex interactions and generate correct follow-up responses. The dorsolateral and dorsomedial parts of the telencephalon in the teleost fish brain are neural substrates modulated by the neurotransmitter dopamine (DA), and are part of an important neural circuitry that drives animal behaviour from the most basic actions such as learning to search for food, to properly choosing partners and managing decisions based on context.