Dopamine disruption increases negotiation for cooperative interactions in a fish.

João P M Messias,Redouan Bshary,José R Paula,Alexandra S Grutter,Marta C Soares

doi:10.1038/srep20817

Abstract

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. We show, in the Indo-Pacific bluestreak cleaner wrasse Labroides dimidiatus, that blocking dopamine receptors in the wild induces cleaners to initiate more interactions with and to provide greater amounts of physical contact to their client fish partners. This costly form of tactile stimulation using their fins is typically used to prolong interactions and to reconcile with clients after cheating. Interestingly, client jolt rate, a correlate of cheating by cleaners, remained unaffected. Thus, in low effective dopaminergic transmission conditions cleaners may renegotiate the occurrence and duration of the interaction with a costly offer. Our results provide first evidence for a prominent role of the dopaminergic system in decision-making in the context of cooperation in fish.

Highlights

Anticipation is crucial is cooperation between unrelated individuals that is based on investments
The five compounds administered consisted of a D1 receptor agonist SKF38393 (D1a) and antagonist SCH23390 (D1an), a D2 receptor agonist Quinpirole (D2a) and antagonist Metoclopramide (D2an), and a saline solution as a control
Cleaner wrasses treated with D1an inspected a significantly higher proportion of clients when compared with the control group (Kruskal-Wallis ANOVA, H (4, N = 50) = 17.4435, p = 0.0016; Dunn’s Post-Hoc test: D1an vs Saline, p = 0.0001, Fig. 1A), whereas other treatments did not differ from the control group (Dunn’s Post-Hoc test: D1a vs Saline, p = 0.4000; D2a vs Saline, p = 0.1451; D2an vs Saline, p = 0.2764, Fig. 1A)

Summary

Introduction

Anticipation is crucial is cooperation between unrelated individuals that is based on investments. As in these previous studies, we exogenously administered a D1 receptor agonist (D1a - SKF38393), an antagonist (D1an SCH23390), a D2 receptor agonist (D2a - Quinpirole) and an antagonist (D2an - Metoclopramide), as well as a control (saline) to female cleaner wrasses in situ As this mutualistic system occurs in a biological market[27,47], efficient dopaminergic transmission could play a role in the modulation of cleaners’ willingness to negotiate with clients over the occurrence and duration of interactions as well as cleaners’ willingness to cooperate rather than cheating[27]. A perceived reduction in the probability of expected outcomes would mean a reduced ability to maintain the interaction with clients and a lower likelihood to obtain food Such perception may, either lead to an extension of negotiation, where high rates of tactile stimulation lead to a reduction of cheating, or to just abandoning negotiation – with cleaners foraging as much and as quickly possible, which would mean immediate cheating by feeding on clients’ mucus[53]

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