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Social living animals have to adjust their behavior to rapid changes in the social environment. It has been hypothesized that the expression of social behavior is better explained by the activity pattern of a diffuse social decision-making network (SDMN) in the brain than by the activity of a single brain region. In this study, we tested the hypothesis that it is the assessment that individuals make of the outcome of the fights, rather than the expression of aggressive behavior per se , that triggers changes in the pattern of activation of the SDMN which are reflected in socially driven behavioral profiles (e.g., dominant vs. subordinate specific behaviors). For this purpose, we manipulated the perception of the outcome of an agonistic interaction in an African cichlid fish (Oreochromis mossambicus) and assessed if either the perception of outcome or fighting by itself was sufficient to trigger rapid changes in the activity of the SDMN. We have used the expression of immediate early genes (c-fos and egr-1) as a proxy to measure the neuronal activity in the brain. Fish fought their own image on a mirror for 15 min after which they were allocated to one of three conditions for the two last minutes of the trial: (1) they remained fighting the mirror image (no outcome treatment); (2) the mirror was lifted and a dominant male that had just won a fight was presented behind a transparent partition (perception of defeat treatment); and (3) the mirror was lifted and a subordinate male that had just lost a fight was presented behind a transparent partition (perception of victory treatment). Results show that these short-term social interactions elicit distinct patterns in the SDMN and that the perception of the outcome was not a necessary condition to trigger a SDMN response as evidenced in the second treatment (perception of defeat treatment). We suggest that the mutual assessment of relative fighting behavior drives these acute changes in the state of the SDMN. [ABSTRACT FROM AUTHOR]

Group living animals must be able to express different behavior profiles depending on their social status. Therefore, the same genotype may translate into different behavioral phenotypes through socially driven differential gene expression. However, how social information is translated into a neurogenomic response and what are the specific cues in a social interaction that signal a change in social status are questions that have remained unanswered. Here, we show for the first time, to our knowledge, that the switch between statusspecific neurogenomic states relies on the assessment of fight outcome rather than just on self- or opponent-only assessment of fighting ability. For this purpose, we manipulated the perception of fight outcome in male zebrafish and measured its impact on the brain transcriptome using a zebrafish whole genome gene chip. Males fought either a real opponent, and a winner and a loser were identified, or their own image on a mirror, in which case, despite expressing aggressive behavior, males did not experience either a victory or a defeat. Massive changes in the brain transcriptome were observed in real opponent fighters, with losers displaying both a higher number of differentially expressed genes and of coexpressed gene modules than winners. In contrast, mirror fighters expressed a neurogenomic state similar to that of noninteracting fish. The genes that responded to fight outcome included immediate early genes and genes involved in neuroplasticity and epigenetic modifications. These results indicate that, even in cognitively simple organisms such as zebrafish, neurogenomic responses underlying changes in social status rely on mutual assessment of fighting ability. [ABSTRACT FROM AUTHOR]

In fluctuating environments, organisms require mechanisms enabling the rapid expression of context-dependent behaviors. Here, we approach behavioral flexibility from a perspective rooted in appraisal theory, aiming to provide a better understanding on how animals adjust their internal state to environmental context. Appraisal has been defined as a multi-component and interactive process between the individual and the environment, in which the individual must evaluate the significance of a stimulus to generate an adaptive response. Within this framework, we review and reframe the existing evidence for the appraisal components in animal literature, in an attempt to reveal the common ground of appraisal mechanisms between species. Furthermore, cognitive biases may occur in the appraisal of ambiguous stimuli. These biases may be interpreted either as states open to environmental modulation or as long-lasting phenotypic traits. Finally, we discuss the implications of cognitive bias for stress research. [ABSTRACT FROM AUTHOR]

Individual variation in the response to environmental challenges depends partly on innate reaction norms, partly on experience-based cognitive/emotional evaluations that individuals make of the situation. The goal of this study was to investigate whether pre-existing differences in behaviour predict the outcome of such assessment of environmental cues, using a conditioned place preference/avoidance (CPP/CPA) paradigm. A comparative vertebrate model (European sea bass, Dicentrarchus labrax) was used, and ninety juvenile individuals were initially screened for behavioural reactivity using a net restraining test. Thereafter each individual was tested in a choice tank using net chasing as aversive stimulus or exposure to familiar conspecifics as appetitive stimulus in the preferred or non preferred side respectively (called hereafter stimulation side). Locomotor behaviour (i.e. time spent, distance travelled and swimming speed in each tank side) of each individual was recorded and analysed with video software. The results showed that fish which were previously exposed to appetitive stimulus increased significantly the time spent on the stimulation side, while aversive stimulus led to a strong decrease in time spent on the stimulation side. Moreover, this study showed clearly that proactive fish were characterised by a stronger preference for the social stimulus and when placed in a putative aversive environment showed a lower physiological stress responses than reactive fish. In conclusion, this study showed for the first time in sea bass, that the CPP/CPA paradigm can be used to assess the valence (positive vs. negative) that fish attribute to different stimuli and that individual behavioural traits is predictive of how stimuli are perceived and thus of the magnitude of preference or avoidance behaviour. [ABSTRACT FROM AUTHOR]

The ability to respond to stress is vital to the survival of any living organism, though sustained reactions can become detrimental to the health and welfare of animals. Stress responses of vertebrates are known through several studies in their physiological, behavioural and psychological components, under acute and chronic contexts. In fish, the physiological and behavioural aspects of stress are considerably well known phenomena and show striking similarities to those of other vertebrates. However, the psychological component is not well known. Some authors deny mental experiences to fish on the basis of their lack of neocortex. Nevertheless, recent studies have shown neuroendocrine, cognitive and emotional processes in fish that are not only equivalent to other vertebrates, but also allow inferring some forms of mental representation. The integration of psychological elements in fish stress physiology is insufficiently studied, but, as discussed in this article, there is already indirect evidence to admit that some form of stimuli appraisal can take place in fish. This fact has profound implications on the regulation of the stress response, as well as on fish welfare and its management. [ABSTRACT FROM AUTHOR]

We previously investigated the androgen responsiveness of males to simulated partner and territory intrusions in five African cichlid species (Neolamprologus pulcher, Lamprologus callipterus, Tropheus moorii, Pseudosimochromis curvifrons, Oreochromis mossambicus; Hirschenhauser et al., 2004). Here we re-analysed data on 11-ketotestosterone (11-KT) levels in holding water to compare the free (presumably from the gills) and conjugated (presumably from urine and faeces) 11-KT fractions. We sampled (i) pre-test baseline control levels from individual males in social isolation and (ii) response levels released after social interactions, either with an ovulating female or a male territory intruder. In four out of five species, conjugated metabolites contributed to the observed total 11-KT responses in water during social context, which was particularly apparent in peak responsive individuals exposed to male intruders. Thus, in water from males sampled in isolation immunoreactive 11-KT seemed to derive both from gills and urine, whereas the urinary 11-KT component apparently increased in the social context, particularly when a male was challenged by a same-sex intruder. These results suggest that (i) the social context may affect urine release patterns of males and (ii) 11-KT data acquired by using fish-holding water may not simply reflect the passive transmission of steroid hormones via the gills. [ABSTRACT FROM AUTHOR]

We measured temporal and spatial components of the waving display in a Uca tangeri population to look for inter-individual differences in male waving structure that may convey information about individual identity. We found evidence that the spatial components of wave structure, especially “Maximum amplitude” are responsible for most of the between-male variation of the display. This variation could reflect differences in individuals’ condition and/or could be used by conspecifics to discriminate amongst familiar and unfamiliar individuals. [ABSTRACT FROM AUTHOR]

Aggressive conflicts between males are often resolved by means of multiple ritualized agonistic displays without damaging escalation. Apparently, in such cases by using those displays opponents exchange important motivational and physical information on which they base a decision to stay or leave the interaction. In the Siamese fighting fish, the time spent spreading the dorsal fin and erecting the gill coverts predicts who will be the winner or loser of the interaction. Two experiments were carried out to study whether display performance might be costly. First, oxygen consumption was measured during mirror-image stimulation. This experiment showed that oxygen consumption was positively correlated with gill cover erection and dorsal fin spread. In the second experiment, a fight between two opponents was simulated and the oxygen consumption of the expected winner and loser was compared. Metabolic rates were not different between winners and losers before and during the fight, but winners showed higher oxygen consumption in the night after the fight. These results are in accordance with costs of display performance and with long-lasting physiological consequences of winning or losing a fight. Aggr. Behav. 32:1–7, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The challenge hypothesis (Wingfield et al. 1990, American Naturalist, 136, 829–846) predicts varying androgen responses to mating, breeding or territorial behaviour in avian males. At the interspecific level, the highest androgen responsiveness has been observed in males from monogamous species with paternal incubation, and the lowest in males from promiscuous, nonpaternal species. Studies of a number of vertebrate species have discussed the extension of the challenge hypothesis predictions to nonavian vertebrates, but a general ‘vertebrate consensus’ has not been achieved. For this quantitative review we included data from all vertebrate species available in the literature into several meta-analyses. We distinguished between the effects of androgens on sexual, aggressive and paternal behaviour and the effects of behaviour on androgen levels and compared these effects between taxa, mating systems and types of parental care. We observed large variations between taxa in all data sets. Nevertheless, at the vertebrate level the challenge hypothesis predictions originating from the avian literature were confirmed for the modulation of androgen responsiveness (1) to sexual behaviour by paternal care but not by mating system, and (2) to paternal behaviour by mating system but not the degree of paternal care. In contrast, our results provide (3) no support for the predicted modulation of androgen levels in response to agonistic interactions by mating and parental care system at the vertebrate level. Furthermore, our meta-analyses suggest that the effects of exogenous testosterone on sexual and agonistic behaviour, as a rule of thumb, may be expected to be larger in nonpaternal than in paternal systems. [Copyright &y& Elsevier]

In general, animals prefer to mate with individuals they have observed being courted or in close association with sexual partners. This phenomenon of mate copying has been demonstrated in several species, but so far no study has provided substantial evidence that it is adaptive. Furthermore, mate copying has been viewed only in the context of females copying other females or males copying other males. In the peacock blenny, Salaria pavo, parasitic males (sneakers) may gain an advantage by copying the association patterns of females with bourgeois males (large males that defend nests). We tested the sneaker''s preference for one of two males and subsequently presented the nonpreferred male to the sneaker in the company of females, while the preferred male was presented alone. If the association of females with bourgeois males influences the sneaker''s preference, we predicted the sneaker would spend more time close to the nonpreferred male, when females were no longer present. We found that (1) sneakers preferred to associate with the larger of the two males and (2) when the previously nonpreferred male was presented in the company of females the sneakers tended to approach that male sooner, although not significantly so, and to spend more time close to it. Thus, parasitic males seem to choose host males both by independent mechanisms (larger males were preferred) and by nonindependent mechanisms (males observed with females were preferred). We discuss the adaptive value of sneakers choosing males by each of these mechanisms. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

Discusses the relationship between social status and male secondary sex traits in cichlid fish at the onset of sexual maturation. Differential expression of morphology and behavioral traits according to social status; Effect of social status on the development of the genital papillae; Predictor of androgen levels in cichlid fishes.

Dominance hierarchies were studied during 8 weeks in eight heterosexual captive groups of Oreochromis mossambicus at the onset of sexual maturity. Linearity was assessed for each group on a weekly basis based on the Landau's index (b) and on the procedure described by Appleby [Appleby MC (1983): Animal Behaviour 31:600-608]. Week-to- week stability of the hierarchical structures was measured using the Burk's stability index (b) and Spearman rank correlation coefficients for the ranks of fishes in consecutive weeks. The two measures of stability showed a high level of concordance but the Spearman rank correlations were more conservative in detecting cases of stability. Although most dominance structures were linear they were unstable from week to week. Dominant individuals were less likely to experience rank reversals than subordinates. Rank reversals were especially likely among hierarchical neighbors. Dominance hierarchies did not stabilize in the time span of this study. [ABSTRACT FROM AUTHOR]

Group living animals can use the behavior of others as cues for the presence of threat in the environment and adjust their behavior accordingly. Therefore, different social phenomena that modulate the response to threat, such as social buffering, social transmission (contagion), and facilitation of alarm responses can be seen as different manifestations of social information use in threat detection. Thus, social phenomena that are functionally antagonistic, such as social buffering and social transmission of fear, may rely on shared neurobehavioral mechanisms related to the use of social information in decision-making about the presence of threat in the environment. Here, we propose a unifying conceptual framework for the study of social information use in threat perception based on signal detection theory. [ABSTRACT FROM PUBLISHER]

Abstract: Many cichlid species dig spawning pits or nests in soft bottoms and exhibit many substrate oriented activities. Despite this fact being of general knowledge, captive cichlids in laboratory and aquaculture set-ups are often kept in the absence of a soft substrate that they can manipulate. This raises a potential welfare issue, depending on how the substrate is valued by cichlid fish. The aim of this study is to assess the importance of substrate for male Mozambique tilapia (Oreochromis mossambicus) in social and non-social contexts. Preferences were established as a measure of time spent in two choice compartments, before and after the presence of a female. Locomotory activity, social interactions and substrate-related behaviours were recorded. Results show that dominant males prefer the area with substrate regardless of social context, and that female''s presence strengthens this preference. The same preference is not apparent in the subordinate males, except for foraging. To draw conclusions on the importance of substrate to subordinates, preferences should also be assessed in agonistic contexts, during which substrate may serve to displace aggression. These results, together with related previous studies, show that the lack of substrate is particularly deleterious in a reproductive context, and thus it is likely to decrease the welfare state of breeding males of Mozambique tilapia. [Copyright &y& Elsevier]

Abstract: Phenotypic change in response to variation in environmental cues has been widely documented in fish. Transitions in social dominance, in particular, have been shown to induce a rapid switch in reproductive phenotypes in many species. However, this effect has been mainly studied in adults and focused on behavioural transitions. The way social cues constraint the phenotypic development of juveniles remains poorly studied in fish. We tested the importance of social dominance and density in the phenotypic development of juveniles of the peacock blenny Salaria pavo. This species shows sequential male alternative reproductive tactics. In the first breeding season males can reproduce as nest-holders or as parasitic males (female-mimicking), or postpone reproduction; from the following season afterwards all males reproduce as nest-holders. Parasitic males have relatively larger testes that lack a testicular gland, present in the testes of nest-holders. The testicular gland is the main source of androgens in the testes and accordingly nest-holders have higher circulating androgen levels. In addition, exogenous androgen administration to parasitic males promotes the development of secondary sexual characters (SSC) only present in nest-holders such as a head crest and an anal gland. We raised juveniles under a high or low-density treatment and monitored social interactions for 1month. No significant effect of density on the development of juvenile males was detected. However, within each replicate, the relative body size of juvenile males at the beginning of the experiment determined their dominance status, with dominant males developing towards the nest-holder morphotype. Dominant males engaged in more nest defence behaviour, showed larger testicular glands, had higher levels of 11-ketotestosterone (11-KT) and testosterone (T) and developed more SSC, as compared to subordinate males. However, these effects of social dominance were moderated by body condition as only dominant males in good body condition developed SSC. The effect of social dominance and of the area of the testicular gland on the development of SSC was mediated by 11-KT and on the expression of nest defence behaviour by T. Interestingly, in spite of the higher androgen levels and more pronounced morphologic development of SSC in dominant individuals, gonadal development was independent of social dominance and most fish still had underdeveloped testis at the end of the experiment. In conclusion, social dominance promoted the development of the testicular gland, an increase in circulating androgen levels and the development of SSC, but did not promote testicular development. This suggests a dissociation of mechanisms underlying sexual maturation and the expression of male reproductive traits. This dissociation seems to be the key for the occurrence of female-mimicking males in this species, which are sexually mature despite lacking the SSC typical of nest-holders. [Copyright &y& Elsevier]