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Animals living in complex social environments are often able to flexibly adjust their behaviour to different social contexts. Yet, flexible responses require time and energy and can be constrained by a variety of mechanisms. Here we asked whether the socio ecological environment experienced by the facultative cleaning goby Elacatinus prochilos influenced their interest in cleaning interactions. Elacatinus prochilos can be found in two socio ecological contexts: inhabiting cleaning stations, where they live in pairs and feed by removing ectoparasites from larger marine organisms (cleaners), or barrel sponges, where they live in dominance hierarchies and rarely engage in cleaning interactions (sponge-dwellers). We tested individuals used in a previous experiment with controlled social structures (small groups with dominance hierarchies) and feeding conditions (better access to food to dominants) to better understand which factors influence cleaning activity in facultative species. We found that dominance significantly decreased cleaning activity in male (and potentially female) sponge-dwellers. We hypothesize that long-term hormone-mediated or time allocation constraints may explain reduced cleaning activity in dominant male sponge-dwellers. While previous studies showed that E. prochilos can be socially flexible, here we showed that feeding flexibility might be restricted for dominant sponge-dwellers. This highlights the importance of testing the flexibility of individuals in different social contexts to better understand the evolutionary importance of adaptive behavioural flexibility. • Facultative cleaning gobies can live in different social and ecological conditions. • We investigated how these differences influenced cleaning interactions. • Dominant individuals from barrel sponges rarely interacted with clients. • This indicates a potential trade-off between dominance and cleaning behaviours. [ABSTRACT FROM AUTHOR]

Cleaning behavior is a well-known example of trophic specialization that is widespread in marine organisms from both tropical and temperate ecosystems. Cleaner species can be more or less specialized in different aspects of cleaning interactions, and it is often assumed that the more specialized cleaners are, the more they rely on clients for food. However, cleaners can consume different items in different sites, and the factors influencing such variation are still poorly understood. Here, we investigated the diet and distribution of the barber goby Elacatinus figaro across marginal reefs of the Brazilian coast. We evaluated E. figaro's reliance on cleaning interactions for food and asked whether its diet and abundance corresponded to the availability of ectoparasites and/or clients. The diet of E. figaro varied across sites, but ectoparasite reliance was similar and did not correspond to client's infestation loads. Moreover, the density of E. figaro did not correlate with the density or richness of potential clients. These support the hypothesis that E. figaro is less reliant on cleaning interactions for food than other cleaning goby species and suggest a high feeding and behavioral plasticity in marginal reefs. This study also highlights that the current dichotomous classification scheme of dedicated versus facultative cleaners fails to capture the subtle nuances of cleaning behavior and should therefore be used with caution in future comparative studies. [ABSTRACT FROM AUTHOR]

Social species often show intraspecific variation in the size and composition of their social units, i.e. the social organization. This variation represents a challenge for comparative studies trying to understand evolutionary transitions in social organization complexity. Most studies on intraspecific variation in social organization (IVSO) have focused on the environmental factors selecting for variation in social organization but the mechanisms underlying such variation remain relatively unexplored. Here we investigated the potential mechanisms giving rise to IVSO in the Caribbean cleaning goby Elacatinus prochilos. This small reef fish typically exhibits two types of social organization, pair living or group living, which not only differ in group size but also in feeding strategy and social behaviour. Pair-living gobies cooperatively feed on ectoparasites removed from larger visiting fish, while group-living gobies feed on microinvertebrates living inside sponges and aggressively defend the best feeding spots against each other. We tested how flexible the social organization, social structure and competition over a food source of E. prochilos are by experimentally manipulating group composition, habitat structure and feeding condition of pair-living and group-living wild adult gobies in laboratory. Despite having different original social organizations in the wild, both pair-living and group-living gobies formed dominance hierarchies and exhibited affiliative behaviours in our group manipulations. This indicates that IVSO in this species is not driven by pre-determined or early-developed mechanisms, but rather a consequence of flexibility in social organization, also known as social flexibility. • We investigated the mechanisms of social organization variation in E. prochilos. • We used a controlled group manipulation to test the behavioural flexibility of individuals. • Individuals exhibiting different social organizations in the wild converged in social behaviour. • This indicates that variable social organization is driven by social flexibility. [ABSTRACT FROM AUTHOR]

The ecological approach to comparative cognition emphasizes that the ecological and social environment are important predictors of cognitive performance. We used this approach to test whether differences in habitat use and social behavior in the facultative Caribbean cleaning goby Elacatinus prochilos predict differences in learning performance in two discriminatory two-choice tasks. This species has two behavioral ecotypes: one that frequently engages in cleaning interactions and inhabits corals in male–female pairs (cleaning gobies) and another that rarely engages in cleaning interactions and inhabits barrel sponges in large groups (sponge-dwellers). We predicted that cleaning gobies would outperform sponge-dwellers in a pattern-cued task, which consisted of identifying the pattern on a plate that consistently provided food, while sponge-dwellers would outperform cleaning gobies in a spatial task, which consisted of identifying the location of the plate. Contrary to our predictions, there was no difference in performance between the two ecotypes. Most of the gobies performed poorly in the pattern-cued task and well in the spatial task. A possible explanation for these results is that the association of a pattern with positive and negative reinforcement may not be a pre-requisite for engaging in cleaning interactions, while spatial skills might be equally required in both ecotypes. Alternatively, the two ecotypes can flexibly adjust to new feeding conditions, which would explain their similar performance in the spatial task. Further research should investigate which aspects of E. prochilos' social and ecological environment might impose challenges that require spatial cognition and whether individuals can flexibly adjust to new habitats and feeding conditions. [ABSTRACT FROM AUTHOR]

The broadstripe cleaning goby Elacatinus prochilos has two alternative ecotypes: sponge-dwellers, which live in large groups and feed mainly upon nematode parasites; and coral-dwellers, that live in small groups or in solitude and behave as cleaners. Recent studies focusing on the skin and gut microbiomes of tropical fish showed that microbial communities are influenced mainly by diet and host species. Here, we compare the skin and gut microbiomes of the Caribbean broadstripe cleaning goby E. prochilos alternative ecotypes (cleaners and non-cleaners) from Barbados and predict that different habitat use and behavior (cleaning vs. non-cleaning) will translate in different bacterial profiles between the two ecotypes. We found significant differences in both alpha- and beta-diversity of skin and gut microbiomes belonging to different ecotypes. Importantly, the skin microbiome of obligate cleaners showed greater intra-sample diversity and harbored a significantly higher prevalence of potential fish pathogens. Likewise, potential pathogens were also more prevalent in the gut of obligate cleaners. We suggest that habitat use, diet, but also direct contact with potential diseased clientele during cleaning, could be the cause for these patterns. [ABSTRACT FROM AUTHOR]

It is proposed herein that the juvenile parrotfish Scarus zelindae is a mimic of the barber goby Elacatinus figaro. Juvenile S. zelindae not only resemble E. figaro but also present changes in behaviour that helps establish the existence of a mimic–model system. When approached by divers juvenile S. zelindae remained stationary at the bottom adopting a site-attached behaviour similar to E. figaro. Because of S. zelindae's colour similarity and behaviour changes, we propose that juvenile S. zelindae may be acting as a mimic to the model E. figaro gaining advantage due to the low rate of predation upon cleaner fish. [ABSTRACT FROM AUTHOR]