Audience effects in Oreochromis mossambicus males on a territorial intrusion context

Dissertação de mestrado em EcologiaIn the natural environment animal communication occurs on a network with several potential signallers and receivers. Given that in a signalling interaction sender and receiver can be observed by a third-party who will collect relevant information, it would be advantageous for those who interact to modulate their behaviour according to the presence of an audience (audience effect). In this study we investigated the audience effect in males of the African cichlid Oreochromis mossambicus. Specifically, we investigated the influence of two factors: i) exposure to an audience (presence/absence); and ii) exposure to an intruder (presence/absence), on the behaviour and steroid hormone levels. We found an audience effect in males’ behaviour resulting in an increase of attention directed towards the audience when intruder is absent, which reveals an interest of the focal male in the audience, and an increase of the agonistic behaviour towards intruders in the presence of the audience. This increase is particularly noticeable in the escalation index, in the frequency of bites and displays. The presence of an audience also had an effect on steroid hormone levels. Cortisol levels were higher in the treatment where the focal male had an audience present but the intruder was absent. Conversely, testosterone levels were higher when the intruder was present and audience was absent. We found positive between interacting behaviours directed to audience and the hormones concentration of 11-ketotestosterone and cortisol. We also found negative correlations between agonistic behaviours and testosterone concentration. Together these results indicate an audience effect in the response to a territorial intrusion, which is inversely related to androgen levels.No ambiente natural a comunicação animal ocorre numa rede com vários potenciais emissores e recetores. Dado que a interação de sinais entre emissor e recetor pode ser observada por terceiros que se podem apropriar de informação relevante, é vantajoso para os intervenientes modular o seu comportamento de acordo com a presença de uma audiência (efeito de audiência). Na presente tese investigámos o efeito de audiência em machos do ciclídeo africano Oreochromis mossambicus. Em particular, investigámos a influência de dois fatores: i) a exposição a uma audiência (presença/ausência); e ii) a exposição a um intruso (presença/ausência), no comportamento e nos níveis hormonais. Foi encontrado um efeito de audiência no comportamento dos machos, resultando no aumento da atenção dirigida à audiência quando o macho estava ausente, o que revela um interesse do macho focal na audiência, e um aumento dos comportamentos agonísticos dirigidos aos intrusos quando a audiência estava presente. Este efeito é particularmente visível no índice de escalada, na frequência de mordidas e de exibições. A presença de uma audiência teve também um efeito nos níveis de hormonas esteroides. Os níveis de cortisol foram mais elevados no tratamento em que o macho focal estava em presença da audiência e com o intruso ausente. Por outro lado, os níveis de testosterona foram mais elevados com o intruso presente e a audiência ausente. Foi detetada uma correlação positiva entre comportamentos de interação dirigidos à audiência e a concentração das hormonas 11-ketotestosterona e cortisol. Foi também detetada uma correlação negativa entre os comportamentos agonísticos e a concentração de testosterona. Em conjunto, estes resultados indicam um efeito de audiência na resposta a uma intrusão territorial, que é inversamente relacionada com os níveis de androgénios.FCT - Fundação para a Ciência e Tecnologia: EXCL/BIA-ANM/0549/201

Rising to the challenge? Inter-individual variation of the androgen response to social interactions in cichlid fish

The Challenge Hypothesis (Wingfield et al. Am. Nat. 136, 829-846) aims to explain the complex relationship between androgens and social interactions. Despite its well acceptance in the behavioral endocrinology literature, several studies have failed to found an androgen response to staged social interactions. Possible reasons for these inconsistencies are the use of single sampling points that may miss the response peak, and the occurrence of inter-individual variability in the androgen response to social interactions. In this study we addressed these two possible confounding factors by characterizing the temporal pattern of the androgen response to social interactions in the African cichlid, Oreochromis mossambicus, and relating it to inter-individual variation in terms of the individual scope for androgen response (i.e. the difference between baseline and maximum physiological levels for each fish) and behavioral types. We found that the androgen response to territorial intrusions varies between individuals and is related to their scope for response. Individuals that have a lower scope for androgen response did not increase androgens after a territorial intrusion but were more aggressive and exploratory. In contrast males with a higher scope for response had fewer aggressive and exploratory behaviors and exhibited two peaks of KT, an early response 2-15 min after the interaction and a late response at 60-90 min post-interaction. Given that the pharmacological challenge of the Hypothalamic-Pituitary-Gonad axis only elicits the late response, we suggest that these two peaks may be regulated by different physiological mechanisms, with the early response being mediated by direct brain-gonad neural pathways. In summary, we suggest that determining the temporal pattern of the androgen response to social interactions and considering inter-individual variation may be the key to understanding the contradictory results of the Challenge Hypothesis.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Forebrain transcriptional response to transient changes in circulating androgens in a cichlid fish

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.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Audience effects in territorial defense of male cichlid fish are associated with differential patterns of activation of the brain social decision-making network

Animals communicate by exchanging signals frequently in the proximity of other conspecifics that may detect and intercept signals not directed to them. There is evidence that the presence of these bystanders modulates the signaling behavior of interacting individuals, a phenomenon that has been named audience effect. Research on the audience effect has predominantly focused on its function rather than on its proximate mechanisms. Here, we have investigated the physiological and neuromolecular correlates of the audience effect in a cichlid fish (Mozambique tilapia, Oreochromis mossambicus). A male was exposed to a territorial intrusion in the presence or absence of a female audience. Results showed that the presence of the female audience increased territorial defense, but elicited a lower androgen and cortisol response to the territorial intrusion. Furthermore, analysis of the expression of immediate early genes, used as markers of neuronal activity, in brain areas belonging to the social decision-making network (SDMN) revealed different patterns of network activity and connectivity across the different social contexts (i.e., audience × intrusion). Overall, these results suggest that socially driven plasticity in the expression of territorial behavior is accommodated in the central nervous system by rapid changes in functional connectivity between nodes of relevant networks (SDMN) rather than by localized changes of activity in specific brain nuclei.Fundação para a Ciência e a Tecnologia (FCT)info:eu-repo/semantics/publishedVersio

Audience Effects in Territorial Defense of Male Cichlid Fish Are Associated with Differential Patterns of Activation of the Brain Social Decision-Making Network

Animals communicate by exchanging signals frequently in the proximity of other conspecifics that may detect and intercept signals not directed to them. There is evidence that the presence of these bystanders modulates the signaling behavior of interacting individuals, a phenomenon that has been named audience effect. Research on the audience effect has predominantly focused on its function rather than on its proximate mechanisms. Here, we have investigated the physiological and neuromolecular correlates of the audience effect in a cichlid fish (Mozambique tilapia, Oreochromis mossambicus). A male was exposed to a territorial intrusion in the presence or absence of a female audience. Results showed that the presence of the female audience increased territorial defense, but elicited a lower androgen and cortisol response to the territorial intrusion. Furthermore, analysis of the expression of immediate early genes, used as markers of neuronal activity, in brain areas belonging to the social decision-making network (SDMN) revealed different patterns of network activity and connectivity across the different social contexts (i.e., audience × intrusion). Overall, these results suggest that socially driven plasticity in the expression of territorial behavior is accommodated in the central nervous system by rapid changes in functional connectivity between nodes of relevant networks (SDMN) rather than by localized changes of activity in specific brain nuclei

Long-term monitoring of the fish community in the Minho Estuary (NW Iberian Peninsula)

The paper presents an extensive fish sampling dataset spanning a long-term period from 2010 to 2019. The data were collected in Lenta Marina, an upstream area in the Minho Estuary of the NW Iberian Peninsula, which belongs to a LTSER (Long-Term Socio-Ecological Research) platform. To capture fish, fyke nets were utilised as the sampling method and deployed at Lenta Marina. This dataset offers valuable insights into the abundance of each collected taxa recorded over time.The dataset reports a comprehensive compilation of data on the abundance of fish species observed in the area during the sampling period (includes zeroes when a given taxonomic entity was absent in a given sampling event). It provides a detailed record of the abundances of the fish community through time in a frequent sampling regime (on average, sampling was done every 6 days). The dataset shows that the amount of fish from invasive taxa exceeds the count of fish from native taxa in the Minho Estuary

Long-term monitoring of the fish community in the Minho Estuary (NW Iberian Peninsula)

The paper presents an extensive fish sampling dataset spanning a long-term period (weekly) from 2010 to 2019. The data was collected in Lenta Marina, an upstream area in the Minho Estuary of the NW Iberian Peninsula. To capture fish, fyke nets were utilized as the sampling method. This dataset offers valuable insights into the abundance of each collected taxa, recorded per date.The dataset reports a comprehensive compilation of fish abundance data, providing a detailed record of how the fish community has changed over time. The dataset clearly shows a trend where the amount of fish from invasive taxa exceeds the count of fish from native taxa