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For male vertebrates, androgens are considered physiological mediators of the trade-off between mating and parenting effort. About 30 years ago, the challenge hypothesis provided a conceptual framework to explain the variation in androgen levels among individuals and species, primarily as a function of male competition and parental care. Initially developed in—and applied to—birds, the challenge hypothesis was rapidly adopted for other vertebrate groups and even insects. Experimental evidence on birds, however, offers limited support for the challenge hypothesis in terms of explaining androgen responses to social challenges from other males. Rather than throwing the baby out with the bathwater, we advance a modified challenge hypothesis 2.0, in which male–female interactions are more important than male–male interactions in mediating rapid changes in plasma androgen concentrations. The predictions we generate are supported by current evidence from birds and can be tested in other animal taxa. [ABSTRACT FROM AUTHOR]

In social species animals should fine-tune the expression of their social behavior to social environments in order to avoid the costs of engaging in costly social interactions. Therefore, social competence, defined as the ability of an animal to optimize the expression of its social behavior as a function of the available social information, should be considered as a performance trait that impacts on the Darwinian fitness of the animal. Social competence is based on behavioral plasticity which, in turn, can be achieved by different neural mechanisms of plasticity, namely by rewiring or by biochemically switching nodes of a putative neural network underlying social behavior. Since steroid hormones respond to social interactions and have receptors extensively expressed in the social behavioral neural network, it is proposed that steroids play a key role in the hormonal modulation of social plasticity. Here, we propose a reciprocal model for the action of androgens on short-term behavioral plasticity and review a set of studies conducted in our laboratory using an African cichlid fish (Oreochromis mossambicus) that provide support for it. Androgens are shown to be implicated as physiological mediators in a wide range of social phenomena that promote social competence, namely by adjusting the behavioral response to the nature of the intruder and the presence of third parties (dear enemy and audience effects), by anticipating territorial intrusions (bystander effect and conditioning of the territorial response), and by modifying future behavior according to prior experience of winning (winner effect). The rapid behavioral actions of socially induced short-term transient changes in androgens indicate that these effects are most likely mediated by nongenomic mechanisms. The fact that the modulation of rapid changes in behavior is open to the influence of circulating levels of androgens, and is not exclusively achieved by changes in central neuromodulators, suggests functional relevance of integrating body parameters in the behavioral response. Thus, the traditional view of seeing neural circuits as unique causal agents of behavior should be updated to a brain–body–environment perspective, in which these neural circuits are embodied and the behavioral performance (and outcomes as fitness) depends on a dynamic relationship between the different levels. In this view hormones play a major role as behavioral modulators. [ABSTRACT FROM PUBLISHER]

The evolution of signals has mainly been considered in the context of an emitter-receiver dyadic interaction. However, communication usually occurs in the presence of individuals (an audience) that are not directly involved in the communication interaction, and it is more realistic to assume that signal evolution occurs in a network. Several types of information could be available to an audience, and, therefore, the presence of an audience could have effects on the behavior of the communicating animals and on signal evolution. We investigated whether the presence of an audience of conspecifics affected intrasexual aggressive communication in male fighting fish. We found that if the audience was a female, males increased the intensity of conspicuous displays that can be used in communication with both males and females and decreased highly aggressive displays that are solely directed to males. If the audience was a male of similar size, there was no significant change in the way in which males displayed. These results suggest that the presence of an audience could be one reason that many long-range and conspicuous signals are often shaped to transmit information to both males and females [ABSTRACT FROM PUBLISHER]

It has been hypothesized that androgens respond to the social interactions as a way to adjust the behavior of individuals to the challenges of the social environment in an adaptive manner. Therefore, it is expected that transient changes in circulating androgen levels within physiological scope should impact the state of the brain network that regulates social behavior, which should translate into adaptive behavioral changes. Here, we examined the effect that a transient peak in androgen circulating levels, which mimics socially driven changes in androgen levels, has on the forebrain state, which harbors most nuclei of the social decision-making network. For this purpose, we successfully induced transient changes in circulating androgen levels in an African cichlid fish (Mozambique tilapia, Oreochromis mossambicus) commonly used as a model in behavioral neuroendocrinology by injecting 11-ketotestosterone or testosterone, and compared the forebrain transcriptome of these individuals to control fish injected with vehicle. Forebrain samples were collected 30 min and 60 min after injection and analyzed using RNAseq. Our results showed that a transient peak in 11-ketotestosterone drives more accentuated changes in forebrain transcriptome than testosterone, and that transcriptomic impact was greater at the 30 min than at the 60 min post-androgen administration. Several genes involved in the regulation of translation, steroid metabolism, ion channel membrane receptors, and genes involved in epigenetic mechanisms were differentially expressed after 11-ketotestosterone or testosterone injection. In summary, this study identified specific candidate genes that may regulate socially driven changes in behavioral flexibility mediated by androgens. [ABSTRACT FROM AUTHOR]