Region specific changes in nonapeptide levels during client fish interactions with allopatric and sympatric cleaner fish

Abstract

Social relationships are crucially dependent on individual ability to learn and remember ecologically relevant cues. However, the way animals recognize cues before engaging in any social interaction and how their response is regulated by brain neuromodulators remains unclear. We examined the putative involvement of arginine vasotocin (AVT) and isotocin (IT), acting at different brain regions, during fish decision-making in the context of cooperation, by trying to identify how fish distinguish and recognize the value of other social partners or species. We hypothesized that the behavioural responses of cleaner fish clients to different social contexts would be underlain by changes in brain AVT and IT levels. We have found that changes in AVT at the level of forebrain and optic tectum are linked with a response to allopatric cleaners (novel or unfamiliar stimuli) while those at cerebellum are associated with the willingness to be cleaned (in response to sympatric cleaners). On the other hand, higher brain IT levels that were solely found in the diencephalon, also in response to allopatric cleaners. Our results are the first to implicate these nonapeptides, AVT in particular, in the assessment of social cues which enable fish to engage in mutualistic activities.

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

“…Indeed, the teleost cerebellum and associated brainstem circuitry is strongly implicated in cognitive and emotional functions, namely in those linked to associative learning and memory processes ( Rodriguez-Ortiz, 2005 ). It is through associative learning that animals learn to anticipate the occurrence of important behavioural outcomes, and perhaps how most of cleaners’ behavioural tactics are acquired ( Soares et al, 2017a ). Brain DA’ neurotransmission is crucial to potentiate the learning process in cleaners (see Messias et al, 2016 ), particularly in situations of novelty ( Soares et al, 2017b ).…”

“…On each experimental day, one of the following treatments was randomly allocated to each subject cleaner wrasses’ aquarium: (a) group A (conspecific, L. dimidiatus , n = 10), (b) group B (client, N. elegans, n = 11), (c) group C (conspecific inside another smaller aquarium, n = 12), (d) group D (client inside another smaller aquarium, n = 10) and (e) group E (white ball, about 5 cm in diameter, which stayed at the bottom, completely sessile; Soares et al, 2017a , n = 10) (see schematic drawing at the Supplemental Information ). Experimental aquaria were divided by opaque partitions that prevented subject client fish from observing other individuals (inside other aquaria) during experiments.…”

Neurobiological and behavioural responses of cleaning mutualisms to ocean warming and acidification

“…We used cleaner wrasses Labroides dimidiatus (n = 32; size 5.4 ± 0.6 cm) and surgeon fish Naso elegans (n = 32, size 6.9 ± 1.1 cm), a frequent client of cleaner wrasses known to be easily adapted to laboratory conditions 43 . These species have been used in behavioural and neurobiological studies and exhibit fully their cooperative cleaning interactions in aquaria even without the presence of parasites.…”

Female reproductive state is associated with changes in distinct arginine vasotocin cell types in the preoptic area of Astatotilapia burtoni

“…These studies also corroborate the restricted distribution of AVT neurons in the POA and hypothalamus characteristic of most teleosts. In addition, HPLC was used to quantify AVT peptide abundance in brain regions and in circulation (Soares et al, 2017). With the rapid expansion and ever‐improving techniques available, more studies are needed that compare methods and visualization techniques to gain a more complete and accurate understanding of biological significance.…”