Artificial selection on relative brain size reveals a positive genetic correlation between brain size and proactive personality in the guppy

Peer reviewe

Boldness Predicts Social Status in Zebrafish (Danio rerio)

This study explored if boldness could be used to predict social status. First, boldness was assessed by monitoring individual zebrafish behaviour in (1) an unfamiliar barren environment with no shelter (open field), (2) the same environment when a roof was introduced as a shelter, and (3) when the roof was removed and an unfamiliar object (Lego® brick) was introduced. Next, after a resting period of minimum one week, social status of the fish was determined in a dyadic contest and dominant/subordinate individuals were determined as the winner/loser of two consecutive contests. Multivariate data analyses showed that males were bolder than females and that the behaviours expressed by the fish during the boldness tests could be used to predict which fish would later become dominant and subordinate in the ensuing dyadic contest. We conclude that bold behaviour is positively correlated to dominance in zebrafish and that boldness is not solely a consequence of social dominance

Bully or Bullied? : The Zebrafish as a Model for Social Stress and Depression

The zebrafish is evaluated as a model for social stress, depression and anxiety. I conclude that it is suitable, especially for studies of sex differences. In humans, women are more prone to depression but most animal studies are performed in males. A popular way to study depression is by means of social stress, which is often a contributing factor to depression. However, social stress in female rodents is difficult to study since female aggression is mostly limited to maternal defence. Thus, there is a need for models to study depression and anxiety in females, as well as sex differences in these disorders. As personality is a risk factor for developing depression, I aimed at exploring correlated behaviours that together characterise personalities. My work confirmed that zebrafish, as numerous other species, show strong correlations between boldness and aggression on the one hand, and neurobiological reactions to social stress on the other. In general, males were bolder than females, but there were no differences in aggressive behaviours between the sexes. It was also confirmed that both acute and chronic social stress activates the dopamine and serotonin systems in the brain, and that subordinate individuals appear to be more stressed, based on serotonergic activity. Further, I studied the consequences of altered levels of serotonin during development, such as would be the case when antidepressants are used during pregnancy. Zebrafish embryos were treated with drugs that affect the serotonin system by increasing or decreasing serotonin levels. Depletion of serotonin increased the expression of several serotonin-related genes but had no effect on morphology. In contrast, increasing serotonin levels only showed small effects on gene expression, but increased the length of the myotomes in the spinal cord. Together with other studies, my results indicate that fluvoxamine might be a suitable choice for treatment of depression during pregnancy. In conclusion, my results show that the zebrafish is a valid model organism for studying social stress, depression and anxiety disorders and it should therefore be considered when developing new animal models for depression. It will especially be beneficial in studies of sex differences

Bully or Bullied? : The Zebrafish as a Model for Social Stress and Depression

The zebrafish is evaluated as a model for social stress, depression and anxiety. I conclude that it is suitable, especially for studies of sex differences. In humans, women are more prone to depression but most animal studies are performed in males. A popular way to study depression is by means of social stress, which is often a contributing factor to depression. However, social stress in female rodents is difficult to study since female aggression is mostly limited to maternal defence. Thus, there is a need for models to study depression and anxiety in females, as well as sex differences in these disorders. As personality is a risk factor for developing depression, I aimed at exploring correlated behaviours that together characterise personalities. My work confirmed that zebrafish, as numerous other species, show strong correlations between boldness and aggression on the one hand, and neurobiological reactions to social stress on the other. In general, males were bolder than females, but there were no differences in aggressive behaviours between the sexes. It was also confirmed that both acute and chronic social stress activates the dopamine and serotonin systems in the brain, and that subordinate individuals appear to be more stressed, based on serotonergic activity. Further, I studied the consequences of altered levels of serotonin during development, such as would be the case when antidepressants are used during pregnancy. Zebrafish embryos were treated with drugs that affect the serotonin system by increasing or decreasing serotonin levels. Depletion of serotonin increased the expression of several serotonin-related genes but had no effect on morphology. In contrast, increasing serotonin levels only showed small effects on gene expression, but increased the length of the myotomes in the spinal cord. Together with other studies, my results indicate that fluvoxamine might be a suitable choice for treatment of depression during pregnancy. In conclusion, my results show that the zebrafish is a valid model organism for studying social stress, depression and anxiety disorders and it should therefore be considered when developing new animal models for depression. It will especially be beneficial in studies of sex differences

Bully or Bullied? : The Zebrafish as a Model for Social Stress and Depression

The zebrafish is evaluated as a model for social stress, depression and anxiety. I conclude that it is suitable, especially for studies of sex differences. In humans, women are more prone to depression but most animal studies are performed in males. A popular way to study depression is by means of social stress, which is often a contributing factor to depression. However, social stress in female rodents is difficult to study since female aggression is mostly limited to maternal defence. Thus, there is a need for models to study depression and anxiety in females, as well as sex differences in these disorders. As personality is a risk factor for developing depression, I aimed at exploring correlated behaviours that together characterise personalities. My work confirmed that zebrafish, as numerous other species, show strong correlations between boldness and aggression on the one hand, and neurobiological reactions to social stress on the other. In general, males were bolder than females, but there were no differences in aggressive behaviours between the sexes. It was also confirmed that both acute and chronic social stress activates the dopamine and serotonin systems in the brain, and that subordinate individuals appear to be more stressed, based on serotonergic activity. Further, I studied the consequences of altered levels of serotonin during development, such as would be the case when antidepressants are used during pregnancy. Zebrafish embryos were treated with drugs that affect the serotonin system by increasing or decreasing serotonin levels. Depletion of serotonin increased the expression of several serotonin-related genes but had no effect on morphology. In contrast, increasing serotonin levels only showed small effects on gene expression, but increased the length of the myotomes in the spinal cord. Together with other studies, my results indicate that fluvoxamine might be a suitable choice for treatment of depression during pregnancy. In conclusion, my results show that the zebrafish is a valid model organism for studying social stress, depression and anxiety disorders and it should therefore be considered when developing new animal models for depression. It will especially be beneficial in studies of sex differences

Social modulation of brain monoamine levels in zebrafish

In social species animals tend to adjust their social behaviour according to the available social information in the group, in order to optimize and improve their one social status. This changing environment requires for rapid and transient behavioural changes that relies primarily on biochemical switching of existing neural networks. Monoamines and neuropeptides are the two major candidates to mediate these changes in brain states underlying socially behavioural flexibility. In the current study we used zebrafish (Danio rerio) males to study the effects of acute social interactions on rapid regional changes in brain levels of monoamines (serotonin and dopamine). A behavioural paradigm under which male zebrafish consistently express fighting behaviour was used to investigate the effects of different social experiences: winning the interaction, losing the interaction, or fighting an unsolved interaction (mirror image). We found that serotonergic activity is significantly higher in the telencephalon of winners and in the optic tectum of losers, and no significant changes were observed in mirror fighters suggesting that serotonergic activity is differentially regulated in different brain regions by social interactions. Dopaminergic activity it was also significantly higher in the telencephalon of winners which may be representative of social reward. Together our data suggests that acute social interactions elicit rapid and differential changes in serotonergic and dopaminergic activity across different brain regions

In situ modeling of multimodal floral cues attracting wild pollinators across environments

With more than 80% of flowering plant species specialized for animal pollination, understanding how wild pollinators utilize resources across environments can encourage efficient planting and maintenance strategies to maximize pollination and establish resilience in the face of environmental change. A fundamental question is how generalist pollinators recognize “flower objects” in vastly different ecologies and environments. On one hand, pollinators could employ a specific set of floral cues regardless of environment. Alternatively, wild pollinators could recognize an exclusive signature of cues unique to each environment or flower species. Hoverflies, which are found across the globe, are one of the most ecologically important alternative pollinators after bees and bumblebees. Here, we have exploited their cosmopolitan status to understand how wild pollinator preferences change across different continents. Without employing any a priori assumptions concerning the floral cues, we measured, predicted, and finally artificially recreated multimodal cues from individual flowers visited by hoverflies in three different environments (hemiboreal, alpine, and tropical) using a field-based methodology. We found that although “flower signatures” were unique for each environment, some multimodal lures were ubiquitously attractive, despite not carrying any reward, or resembling real flowers. While it was unexpected that cue combinations found in real flowers were not necessary, the robustness of our lures across insect species and ecologies could reflect a general strategy of resource identification for generalist pollinators. Our results provide insights into how cosmopolitan pollinators such as hoverflies identify flowers and offer specific ecologically based cues and strategies for attracting pollinators across diverse environments