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Freshwater fishes exhibit a wide range of auditory adaptations and capabilities, which are assumed to help them navigate their environment, avoid predators, and find potential mates. Yet, we know very little about how freshwater environments sound to fish, or how fish with different auditory adaptations respond to different soundscapes. We first compiled data on fish hearing acuity and adaptations and provided a portrait of how anthropogenic sounds compare to natural sounds in different freshwater soundscapes. We then conducted a sound‐enrichment field experiment at Lake Saint Pierre, a large fluvial lake in Canada, to evaluate the effect of motorboat sound exposure on the fish community by looking at the extent to which changes in species abundances were linked to auditory adaptations. Data compilation showed that the hearing acuity of most species overlaps with a wide range of ambient and anthropogenic underwater sounds while the field experiment showed that species with more specialized auditory structures were captured less often in sound‐enriched traps, indicating avoidance behavior. Our findings highlight the importance of considering species' sensorial adaptations when evaluating the community‐scale effects of anthropogenic sounds on the fish community, especially at low levels of anthropogenic activity. [ABSTRACT FROM AUTHOR]

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]

Individual decisions about whether or not to disperse shape the kin structure of social groups, promoting or disrupting the evolution of sociality via kin selection. It is often assumed that the great dispersal potential of marine larvae driven by ocean currents disrupts kin association and, as a consequence, reduces the chances that social groups in the sea form via kin selection. Yet, accumulating evidence indicates that the larval dispersal process is not as random as previously assumed and that different mechanisms can promote kin associations in marine species. Here, we review recent findings in the marine larval ecology literature, emphasizing key aspects of larval development that may limit or promote dispersal and the evolution of sociality in the sea. We find ample evidence that marine larvae settle closer to home than has been previously assumed. A variety of different mechanisms, including lack of planktonic dispersal, limited larval duration, larvae traveling together, variability in reproductive success, and behavioral and physical processes, can generate kin association in marine species and potentially lead to the formation of social groups via kin selection. Uncovering post‐settlement dispersal patterns is also important for understanding how groups of unrelated individuals are formed. By integrating different larval dispersal strategies into the dual benefit framework for the evolution of sociality, we provide examples of alternative pathways for the evolution of sociality in marine species. Finally, we discuss how the increased use of parentage analysis in marine species will provide an opportunity for investigating whether kin selection is indeed much rarer in marine than terrestrial species. Ultimately, determining the role that dispersal and kin selection play in the evolution of sociality in marine species will require an increased effort to gather both behavioral and genetic data for the same species. [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]

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]

Mathematical modelling regarding evolutionary theory typically assumes that optimal strategies are not constrained through mechanistic processes. In contrast, recent studies on brain anatomy and neurobiology suggest that flexibility in social behaviour is rather constrained by the physiological state of the social decision-making network. Changing its state may yield selective advantages in some social contexts but neutral or even detrimental effects in others. Here we provide field evidence for such physiological trade-offs. We subjected wild female cleaner wrasse to injections of testosterone or of saline solution (control) and then observed both intraspecific interactions and interspecific cleaning behaviour with other reef fish, referred to as clients. Testosterone-treated females intensified intraspecific social interactions, showing more aggression towards smaller females and tendencies of increased aggressive and affiliative contacts with dominant males. Such testosterone-mediated changes fit the hypothesis that an increase in testosterone mediates female's focus on status in this protogynous hermaphrodite species, where females eventually change sex to become males. Moreover, we also identified other effects on interspecific social interactions: testosterone-treated females interacted less with client reef fishes and hence obtained less food. Most importantly, they selectively reduced service quality for species that were less likely to punish after being cheated. Overall, our findings suggest that testosterone causes pleiotropic effects on intra and interspecific social behaviour by broadly influencing female cleaners' decision-making. [ABSTRACT FROM AUTHOR]

Aim: Several drivers explain the global distribution of all reef fish. However, whether these drivers also explain the distribution and traits of a functional subgroup involving cleaner fishes remain unclear. Here we examine the variation in traits of cleaner fishes and test whether historical, environmental, ecological and geographical drivers are correlated with cleaner species richness and abundance at global reefs. Location: Tropical and subtropical reefs. Taxon: Actinopterygii. Methods: We tested whether species traits and trait space vary between facultative (i.e. species that clean only during the juvenile stages or sporadically) and dedicated (i.e. species that clean during their whole lives) cleaner types. We compiled data from local checklists (relative richness) and belt transects (standardized richness and abundance). We built four models to test whether past and current isolation (i.e. distance from Quaternary refugia and biodiversity centres), sea temperature, primary productivity, local species pool and abundance of potential clients influenced the relative richness and abundance of cleaners. Results: Facultative cleaners had high trait variability that contributed disproportionally to the trait space, whereas dedicated cleaners exhibited low trait variability. Cleaner species richness was higher in the Indo‐Pacific and Caribbean provinces, but the relative richness and standardized abundance of cleaners were higher in the Atlantic (i.e. North Eastern and Southwestern) and Eastern Pacific. Isolation influenced the relative richness of facultative cleaners, whereas the distance to Quaternary refugia, sea temperature and isolation influenced the relative richness of dedicated cleaners. Local species richness and standardized abundance of cleaner fish exhibited a strong relationship with regional diversity. The standardized abundance of both facultative and dedicated cleaners was influenced by the abundance of potential clients and the local species pool. Main conclusions: The small trait space occupied by cleaner fishes may reflect their restricted origin among lineages of reef fishes. Differences in the relative richness and standardized abundance of cleaner fishes across marine realms suggest a strong influence on biogeographical history. Our results also indicate that cleaner fishes originated mostly in peripheral areas in high latitudes due to the absence of dedicated cleaners. Our results imply that cleaner fishes do not follow the pattern of main centres of origin described for reef fishes due to opportunistic cleaning behaviour that originated with higher frequency at locations with low species richness. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]