Bold Fish Research Articles

Comparative study of long chain polyunsaturated fatty acids (LC-PUFA) accumulation in bold and shy Eurasian perch (Perca fluviatilis)

Inspired from discussions around human dietetics and behavioral traits, the study presumed that bold fish may have better long chain polyunsaturated fatty acids (LC-PUFA) accumulation strengths than shy fish, when subjected to a common food. Using Eurasian perch (Perca fluviatilis) model similar in age and sexually immature, it was investigated whether any statistically significant difference in the LC-PUFA accumulation from food to liver or brain between size-matched bold and shy individuals exist. Results suggest an enhanced accumulation of LC-PUFAs such as arachidonic acid (ARA, 20:4n-6), eicosatrienoic acid (ETA, 20:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid (DPA, 22:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) happen from feed (p < 0.05) to either liver or brain. However, we found no statistically significant difference (p > 0.05) in overall fatty acids profile or LC-PUFA of liver or brain between bold and shy individuals, neither any differences in potential eicosanoid actions (as mediated by LC-PUFAs ARA: EPA ratio) in their brain or liver, when fed a common feed/ lipid source. As such the original presumption was rejected. The bold and shy Eurasian perch are similar in their capabilities to selectively incorporate or endogenously fortify LC-PUFA content. The study concludes that the endogenous pool or stoichiometry of LC-PUFAs seem unrelated to boldness or shyness in fish. The managerial implication of the findings is to better link the behavioral traits in aquaculture or fish ethology to nutrition and physiology.

Individual differences in the boldness of female zebrafish are associated with alterations in serotonin function.

One of the most prevalent axes of behavioral variation in both humans and animals is risk taking, where individuals that are more willing to take risk are characterized as bold while those that are more reserved are regarded as shy. Brain monoamines (i.e. serotonin, dopamine and noradrenaline) have been found to play a role in a variety of behaviors related to risk taking. Using zebrafish, we investigated whether there was a relationship between monoamine function and boldness behavior during exploration of a novel tank. We found a correlation between serotonin metabolism (5-HIAA:5-HT ratio) and boldness during the initial exposure to the tank in female animals. The DOPAC:DA ratio correlated with boldness behavior on the third day in male fish. There was no relationship between boldness and noradrenaline. To probe differences in serotonergic function in bold and shy fish, we administered a selective serotonin reuptake inhibitor, escitalopram, and assessed exploratory behavior. We found that escitalopram had opposing effects on thigmotaxis in bold and shy female animals: the drug caused bold fish to spend more time near the center of the tank and shy fish spent more time near the periphery. Taken together, our findings indicate that variation in serotonergic function has sex-specific contributions to individual differences in risk-taking behavior.

Are lateralized and bold fish optimistic or pessimistic?

Cognitive bias is defined as the influence of emotions on cognitive processes. The concept of the cognitive judgement bias has its origins in human psychology but has been applied to animals over the past 2 decades. In this study we were interested in determining if laterality and personality traits, which are known to influence learning style, might also be correlated with a cognitive bias in the three-spined sticklebacks (Gasterosteus aculeatus). We used the judgement bias test with the go/no-go procedure where fish were first trained to discriminate between a black and white card and, after reaching a minimum learning criterion, tested their response to an ambiguous card (grey). Optimistic subjects were expected to have a high expectation of reward associated with an ambiguous stimulus, whereas pessimistic subjects a high expectation of non-reward. We used an emergence and a mirror test to quantify boldness and laterality, respectively. We hypothesised that male, bolder and more strongly lateralized fish would be more optimistic than female, shy and less strongly lateralised fish. We found that males and more strongly lateralized fish were more optimistic than females and less strongly lateralized fish. In addition, bold males were more optimistic than shy males as we predicted, but females showed the opposite pattern. Finally, fish trained on the black colour card learned the training task faster than those trained on a white card. Our results indicate that both laterality and personality traits are linked to animals’ internal states (pessimistic or optimistic outlooks) which likely has broad implications for understanding animal behaviour particularly in a welfare context.

Shy and Bold Fish Have the Same Preference for Light Color Selection.

Personality, which matters for animal welfare, demonstrates behavioral differences. Light is one of the most important factors in aquaculture. However, how fish personality affects light color selection is unclear. In this study, we tested the personality of yellow catfish Pelteobagrus fulvidraco juveniles and then quantified the selective behaviors of different personalities under six light colors: violet (410-420 nm), yellow (580-590 nm), green (550-560 nm), red (620-630 nm), blue (470-480 nm), and white. The results showed that juveniles preferred the yellow and green light over the other colors of light, probably due to different reasons. The average cumulative dwell time in yellow (32.81 ± 5.22%), green (21.81 ± 3.58%), and red (26.36 ± 4.89%) lights was significantly longer than the other light colors, and the average visit frequency in green light (32.00 ± 4.93%) was the most. Juveniles had the longest total moved distance in green light. Moreover, the results demonstrated that shy and bold individuals had the same preference for the green light. Bold individuals could find the preferred light colors rapidly and make quick decisions for light color selection. After identifying the preferred light colors, bold individuals reduced the frequency of exploration. This study provides a theoretical basis for the welfare of juvenile yellow catfish in aquaculture.

Individual differences in response to alcohol and nicotine in zebrafish: Gene expression and behavior.

Alcohol and nicotine are psychoactive substances responsible for serious health consequences. Although the biological mechanisms of alcohol and nicotine have been studied extensively, individual differences in the response to these drugs have received little attention. Here we evaluated gene expression and behavior of bold and shy individuals after acute exposure to alcohol and nicotine. For this, zebrafish were classified as bold and shy individuals based on emergence tests, and then fish were exposed to 0.00, 0.10, and 0.50% alcohol or 0.00, 1.00, and 5.00 mg/L nicotine and their anxiety-like and locomotor behavior was observed. After behavioral assessment, brain mRNA expression (ache, bdnf, gaba1, gad1b, th1, and tph1) was evaluated. Locomotion patterns differed between profiles depending on alcohol and nicotine concentration. Anxiety increased in shy fish and decreased in bold fish after exposure to both drugs. Alcohol exposure induced an increase in tph1 mRNA expression in bold fish, while bdnf mRNA expression was increased in shy fish. Nicotine increased ache, bdnf, and tph1 mRNA levels in both profiles, but at higher levels in bold fish. Based on our research, we found that alcohol induces anxiogenic effects in both bold and shy zebrafish. Additionally, shy individuals exposed to a low concentration of nicotine exhibited stronger anxiety-like responses than their bold counterparts. These findings further support the validity of using zebrafish as a dependable tool for studying the effects of drugs and uncovering the underlying mechanisms associated with individual variations.

Correlations begin at home: drivers of co-occurrence patterns in personality and cognitive ability in wild populations of zebrafish.

Aquatic habitats are extremely dynamic, with constantly changing ecological factors, which has now been exacerbated due to human-induced rapid environmental change. In such variable environments, it becomes essential to understand how personality and cognition in organisms affect the adaptability of individuals to different habitat conditions. To test this, we studied how personality-related traits as well as cognitive ability differ between populations of wild-caught zebrafish (Danio rerio) from habitats that differed in various environmental factors. We measured emergence into a novel environment as an indicator of boldness, and performance in a spatial task inferred from feeding latencies in a maze over repeated trials to assess learning and memory, as an indicator of cognitive ability. We found that personality affects cognition and although bolder fish are better learners, they show poorer retention of memory across populations. Although personality and cognitive ability varied between habitats, the patterns of their correlations remained similar within each population. However, the individual traits (such as sex and size) that were drivers of personality and cognition differed between the habitats, suggesting that not only do behavioral traits vary between populations, but also the factors that are important in determining them. Personality and cognitive ability and the correlations between these traits determine how well an organism performs in its habitat, as well as how likely it is to find new habitats and adapt to them. Studying these across wild zebrafish populations helps predict performance efficiencies among individuals and also explains how fish adapt to extremely dynamic environments that can lead to variation in behavioral traits and correlations between them. This study not only sheds light on the drivers of interindividual variation and co-occurrence patterns of personality and cognition, but also individual and population factors that might have an effect on them.

Behaviour of personality-screened juvenile Oreochromis niloticus in different challenges: Bold fish present more exploratory capacity and learning to face imposed challenges.

The investigation of cultivation and management techniques that take into account behaviour and animal welfare becomes important due to their direct relationship with animal performance. This study aimed to classify juvenile Oreochromis niloticus by personality and compare their performance at exploration and competition tasks. The new object test was used to select bold and shy animals, which were then tested to see which first approached an object. The food competition test involved placing three feed pellets inside a cylinder and measuring the time taken until the pellet was eaten. The new object test found bold animals with a shorter mean time to approach the object than shy animals approaching 65% of the first object when compared to shy. The food competition test found that the bold animals ingested the first pellet more times and with a shorter average time of ingestion than shy animals, no difference in the second intake, whereas the results for the third were same as those for the first. Shy animals had higher intake of the second pellet. Bold animals explored their environment faster in both challenges, while shy individuals exhibited ability to learn from the challenges imposed in the study.

The effect of sex, age and boldness on inhibitory control

Inhibitory control requires an individual to suppress impulsive actions in favour of more appropriate behaviours to gain a delayed reward. It plays an important role in activities such as foraging and initiating mating, but high within-species variation suggests that some individuals have greater inhibitory control than others. A standard index of inhibitory control used in many taxa is measuring how long an animal persists in trying to move itself or an appendage (e.g. its hand) through a transparent barrier to reach a reward. Although recent nonhuman studies have investigated how different factors are associated with variation in inhibitory control, these studies have rarely considered how these factors interact. Here we investigated how sex, age, personality (boldness) and the type of reward stimulus interact to predict the degree of motor inhibitory control in eastern mosquitofish, Gambusia holbrooki . We measured inhibitory control using a standard detour assay, ‘boldness’ (time to emergence in a novel environment), and the rate of learning. There were three different reward stimuli: a shoal of females, a shoal of males or a mixed-sex shoal. Individuals were tested in four consecutive trials, always with the same reward type, to quantify short-term learning. These measures were repeated at 7, 14 and 21 weeks after maturation to examine the effect of age. Females had significantly greater inhibitory control than males. Regardless of sex, older fish had significantly greater inhibitory control than younger fish, and boldness predicted learning ability. The type of reward stimuli had no sex-specific effect on inhibitory control. We discuss the biological significance of these sources of variation in inhibitory control, and the importance of accounting for them in studies examining individual differences in cognitive abilities. • Inhibitory control (IC) suppresses impulsive actions in favour of delayed rewards. • Both sex and age, but not their interaction, affected IC in 251 mosquitofish. • Individual's boldness did not affect IC, but bolder fish were faster learners. • Composition of a social reward (males/females/mixed) did not affect IC.

High risk of predation suppresses behavioural differences among bold and shy social prey individuals

Abstract Prey animals must attempt to optimize foraging success while reducing the probability of being captured. Within social prey groups, intrinsic differences in bold-shy personality among individuals influence their respective risk-taking tendencies. We examined the foraging and refuge use behaviour of mixed groups of goldfish (Carassius auratus) containing half bold individuals and half shy individuals under variable levels of predation risk from a live avian predator (Egretta garzetta). At the group level, the fish groups significantly decreased their foraging time by spending more time under the refuge when the predator spent more time at the focal pool. As expected, the bold fish tended to be the first to leave the refuge, and foraged outside the refuge more often than shy fish under control conditions and at lower risk levels. However, the behavioural differences between bold and shy fish disappeared under higher risk conditions. In terms of mortality, the predator captured significantly more bold fish than shy fish. Our study illustrates how bold individuals in social groups often take greater risks to achieve foraging success, but demonstrates that innate differences in boldness can be diminished in times of elevated predation risk.

Investigating the physiological response and antibody concentration of gilthead sea bream (Sparus aurata) following Vibrio anguillarum vaccination depending on the stress coping style

Stress coping styles (SCSs) are defined as coherent sets of individual physiological and behavioral differences in stress response consistent across time and context and are described in a wide range of taxa, including fishes. These differences in behavior and physiology are of great interest because they may have direct implications on animal health, welfare, and performance in farming systems, including aquaculture. In this study, the physiological responses of sea bream (Sparus aurata) from different SCSs following Vibrio anguillarum vaccination were monitored. Fish were first screened either bold or shy (proxy of proactive and reactive SCSs, respectively) using group risk-taking tests and were then injected with a vaccine against V. anguillarum. Following vaccination, the fish were implanted with an accelerometer tag to monitor their swimming activity (proxy of energy expenditure), and blood sampling was carried out to measure health and welfare parameters (e.g., cortisol, glucose, hemoglobin) and aspecific immunity (e.g., protease, total proteins). In addition, blood was also collected at three different sampling times to screen antibody levels and, thus, to evaluate the efficiency of the vaccine. Following vaccination, bold fish displayed lower swimming activity values, indicative of lower energy expenditure, and also displayed higher levels of hematocrit, total proteins, and lysozyme in the plasma than the shy ones, which could be indicative of better health/welfare status and greater aspecific immunity. Finally, the V. anguillarum vaccination appeared to be more efficient in bold fish since the number of total antibodies was found higher than in shy fish 1 month after vaccination. Such results could help improve both health/welfare and productivity of farmed sea breams by selecting more robust fish, better adapted to farming conditions.

Boldness Predicts Aggressiveness, Metabolism, and Activity in Black Rockfish Sebastes schlegelii

Animal personality refers to individual behavioral and physiological differences that are consistent over time and across context. Recently, the fish personality has gained increasing attention, especially from the perspective of aquaculture production. Here, we used an important aquaculture species, black rockfishSebastes schlegelii, as the target animal, and conducted a series of experiments to explore the relationships among fish boldness, aggressiveness, locomotor activity, opercular beat rate, standard metabolic rate, and cortisol level. Generally, the results showed that the boldness of black rockfish was significantly, positively correlated with fish aggressiveness, stressed locomotor activity, and standard metabolic rate, while was negatively correlated with stressed opercular beat rate. Bold fish had significantly higher aggressiveness, standard metabolic rate, and stressed locomotor activity but lower stressed opercular beat rate. However, there were no significant correlations between boldness and basal locomotor activity or between boldness and basal cortisol level. These results preliminarily constructed the behavioral and physiological spectrum of black rockfish in the context of fish personality and clearly indicated that the boldness could be used as a discrimination tool to predict fish aggressiveness and metabolic rate, which may have valuable applications for decreasing fish harmful aggression and increasing fish welfare in the aquaculture industry.

Suppression of personality variation in boldness during foraging in three-spined sticklebacks

Consistent inter-individual variation in behaviour within a population, widely referred to as personality variation, can be affected by environmental context. Feedbacks between an individual’s behaviour and state can strengthen (positive feedback) or weaken (negative feedback) individual differences when experiences such as predator encounters or winning contests are dependent on behavioural type. We examined the influence of foraging on individual-level consistency in refuge use (a measure of risk-taking, i.e. boldness) in three-spined sticklebacks, Gasterosteus aculeatus, and particularly whether changes in refuge use depended on boldness measured under control conditions. In the control treatment trials with no food, individuals were repeatable in refuge use across repeated trials, and this behavioural consistency did not differ between the start and end of these trials. In contrast, when food was available, individuals showed a higher degree of consistency in refuge use at the start of the trials versus controls but this consistency significantly reduced by the end of the trials. The effect of the opportunity to forage was dependent on behavioural type, with bolder fish varying more in their refuge use between the start and the end of the feeding trials than shyer fish, and boldness positively predicted the likelihood of feeding at the start but not at the end of the trials. This suggests a state-behaviour feedback, but there was no overall trend in how bolder individuals changed their behaviour. Our study shows that personality variation can be suppressed in foraging contexts and a potential but unpredictable role of feedbacks between state and behaviour.Significance statementIn this experimental study, we examined how foraging influences consistency in risk-taking in individual three-spined sticklebacks. We show that bolder individuals become less consistent in their risk-taking behaviour than shyer individuals during foraging. Some bolder individuals reinforce their risk-taking behaviour, suggesting a positive feedback between state and behaviour, while others converge on the behaviour of shyer individuals, suggesting a negative feedback. In support of a role of satiation in driving negative feedback effects, we found that bolder individuals were more likely to feed at the start but not at the end of the trials. Overall, our findings suggest that foraging can influence personality variation in risk-taking behaviour; however, the role of feedbacks may be unpredictable.

Predator kairomones elicit bold, exploratory behaviours in juvenile bluegill, Lepomis macrochirus

Behavioural responses of animals are often placed conceptually along some axis characterized by the extremes, e.g. bold versus shy or timid. Ecological and evolutionary pressures can be associated with increased frequencies of different behavioural patterns that are also subject to intrinsic factors such as differing metabolic requirements or cognitive abilities. We exposed individual wild-caught juvenile bluegill, Lepomis macrochirus, to kairomones from predatory northern pike, Esox lucius, or to lake water controls during a Z-maze arena assay commonly used to assess relative levels of boldness and exploratory behaviours. Fish were subsequently lethally sampled for liver and brain mass to obtain estimates of relative body condition (hepato-somatic index, HSI) and cognitive capacity (brain-somatic index, BSI), as well as the state of the gallbladder, to test for relationships between these indices and observed boldness-related behaviours. Using principal components analysis (PCA) we identified a boldness–exploration syndrome in bluegill independent of chemical treatment and body metrics where bolder fish emerged from a start chamber in less time, travelled farther through the maze and crossed more lines than less bold fish. Bluegill exposed to kairomones were bolder on average than their counterparts in the control treatment independent of body metrics, suggesting that elevated risk levels indicated by predator kairomones can elicit behavioural responses consistent with boldness, exploration and risk taking. The role of relative cognitive ability in the expression of boldness and exploration is equivocal and may be resolved through repeated assays on individuals at different risk levels.

Personality composition determines social learning pathways within shoaling fish.

In shaping how individuals explore their environment and interact with others, personality may mediate both individual and social learning. Yet increasing evidence indicates that personality expression is contingent on social context, suggesting that group personality composition may be key in determining how individuals learn about their environment. Here, we used recovery latency following simulated predator attacks to identify Trinidadian guppies (Poecilia reticulata) that acted in a consistently bold or shy manner. We then employed network-based diffusion analysis to track the spread of a novel foraging behaviour through groups containing different proportions of bold and shy fish. Informed associates promoted learning to a greater extent in bold individuals, but only within groups composed predominately of bold fish. As the proportion of shy fish within groups increased, bold individuals instead emerged as especially effective demonstrators that facilitated learning in others. Individuals were also more likely to learn overall within shy-dominated groups than in bold-dominated ones. We demonstrate that whether and how individuals learn is conditional on group personality composition, indicating that selection may favour traits enabling individuals to better match their behavioural phenotype to their social environment.

Zebrafish Danio rerio shows behavioural cross-context consistency at larval and juvenile stages but no consistency between stages.

Coping style is defined as a set of individual physiological and behavioural characteristics that are consistent across time and context. In the zebrafish Danio rerio, as well as in many other animals, several covariations have been established among behavioural, physiological and molecular responses. Nonetheless, not many studies have addressed the consistency in behavioural responses over time starting at the larval stage. Therefore, this study aimed to improve the understanding of behavioural consistency across contexts and over time in zebrafish from the larval to juvenile stages. Two distinct experiments were conducted: a larval stage experiment (from 8 to 21 days post fertilization, dpf) and a juvenile stage experiment (from 21 to 60 dpf). On one hand, the larval experiment allows to focus on the transition between 8 and 21 dpf, marked by significant morphological changes related to the end of larval stage and initiation of metamorphosis. On the other hand, the juvenile experiment allows to properly cover the period extending from the end of larval stage to the juvenile stage (60 dpf), including metamorphosis which is itself completed around 45 dpf. Within each experiment, boldness was determined using a group risk-taking test to identify bold and shy individuals. A novel environment test was then performed at the same age to evaluate consistency across contexts. Groups of fish (either bold or shy) were bathed in an alizarin red S solution for later identification of their initially determined coping style to evaluate behavioural consistency over time. Fish were then reared under common garden conditions and challenged again with the same behavioural tests at a later age (21 and 60 dpf in the larval and juvenile experiments, respectively). Behavioural consistency was observed across contexts, with bold fish being more active and expressing higher thigmotaxis regardless of age. There was, however, little behavioural consistency over age, suggesting behavioural plasticity during development. Moreover, the use of alizarin red S to conduct this experiment provides new perspectives for the further study of the longitudinal evolution of various traits, including behaviour, over life stages in fish.

Personality- and size-related metabolic performance in invasive round goby (Neogobius melanostomus)

Differences between individuals in behavioral type (i.e. animal personality) are ecologically and evolutionarily important because they can have significant effects on fitness components such as growth and predation risk. In the present study we are used the invasive round goby (Neogobius melanostomus) from an established population in controlled experiments to examine the relationships among personality, metabolic performance, and growth rate (inferred as size-at-age). Boldness was measured as the time to return to normal behavior after a simulated predator attack, where fish with shorter freezing times were categorized as “bold” and fish with longer times were categorized as “shy.” We show that bold fish have significantly higher standard metabolic rate (SMR) than their shy conspecifics, whereas there was no difference between personality types in their maximum metabolic rate (MMR) or aerobic scope (AS). Bold fish furthermore had a smaller size-at-age as compared to shy fish. Together this provides evidence of a metabolic underpinning of personality where the high-SMR bold fish require more resources to sustain basic life functions than their low-SMR shy conspecifics, indicating that bold round goby from established populations with high densities (and high competition for food) pay a price of reduced growth rate.

Personality, plasticity and predictability in sticklebacks: bold fish are less plastic and more predictable than shy fish

It is well established that animals often differ consistently from one another in their behaviour. Most work has focused on consistent differences in average behaviour, generally referred to as ‘animal personality’. However, individuals may also differ consistently from one another in how they change their behaviour over time or across environments, that is, plasticity, as well as in the predictability of their behaviour. How these three sources of behavioural variation are linked is rarely explored. Here we tested 80 wild-caught three-spined sticklebacks, Gasterosteus aculeatus, repeatedly over a 10-week period for their tendency to explore an open arena from the safety of cover, generally termed ‘boldness’. Using a mixed-modelling approach, we detected consistent individual differences in boldness, as well as in the extent to which fish changed this behaviour over time, that is, temporal plasticity. Boldness and plasticity were negatively correlated, with shy fish spending increasing amounts of time out of cover while bold fish changed little over time. After accounting for variation in personality and plasticity, we still detected individual differences in intraindividual behavioural variation (‘IIV’), that is, individual predictability. This residual variation was linked to fish’ boldness score, with shy fish having higher IIV and thus being less predictable in their behaviour than bold fish. After a 4-week break from testing, individuals on average decreased their time out of cover again to baseline levels. However, shyer, more plastic fish showed the largest changes in behaviour. Statistical simulations show that our experimental data set has sufficient statistical power to provide accurate and precise variance parameter estimates. Together, our results provide strong evidence that individual variation in boldness is linked with behavioural plasticity and predictability. Establishing the evolutionary causes as well as fitness consequences of these links in behavioural variation is an exciting challenge for future research.

Coping styles in European sea bass: The link between boldness, stress response and neurogenesis

Coping styles consist of a coherent set of individual physiological and behavioral differences in stress responses that are consistent across time and context. Such consistent inter-individual differences in behavior have already been shown in European sea bass (Dicentrarchus labrax), but the associated mechanisms are still poorly understood. Here, we combine physiological measurements with individual behavioral responses in order to characterize coping styles in fish. Fish were tagged and placed in a tank for group risk-taking tests (GRT) at 8 months of age to evaluate boldness using the proxy latency of leaving a sheltered area towards an open area. A subsample of these fish were individually challenged 16 months later using an open field test (OFT), in which the boldness was assessed after being placed in a shelter within an open arena. Latency to exit the shelter, time spent in the shelter, and distance travelled were recorded for this purpose. The blood and brain were then collected to evaluate plasma cortisol concentration and neurotransmitter levels (dopamine, norepinephrine, serotonin, and related metabolites), as well as brain transcription of key genes involved in stress axis regulation (gr1, gr2, mr, crf), neurogenesis (neurod1, neurod2, pcna), and neuronal development (egr1). Fish acting bolder in the GRT were not necessarily those acting bolder in the OFT, highlighting the relatively low consistency across different types of tests performed with a 16-months interval. There was, however, a significant correlation between stress markers and boldness. Indeed, mRNA levels of mr, crf, gr2, egr1, and neurod2, as well as norepinephrine levels were higher in shy than bold fish, whereas brain serotonergic activity was lower in shy fish. Overall, our study highlights the fact that boldness was not consistent over time when testing context differed (group vs. alone). This is in agreement with previous literature suggesting that social context play a key role in boldness measurement and that the particular life history of each individual may account in shaping the personality fate of a fish.

Relationships between personality and lateralization of sensory inputs

In humans and other vertebrates, sensory information is sometimes lateralized towards one brain hemisphere that dominates the control of a task. Although sensory lateralization may depend on the stimuli being processed, the degree or direction of lateralization can differ according to behavioural phenotype. Accordingly, personality may play an important role in lateralization, yet there is a lack of evidence regarding how lateralizations are utilized to process information and promote a personality-based response to a particular situation. Here we show that simultaneous stimulus processing and organization of personality-based responses can be accomplished via differences in laterality between senses. We demonstrate this by examining novel object inspection in the weakly electric fish Gnathonemus petersii. We found that electrosensing is lateralized in this species, but differently between personality phenotypes: bold fish were lateralized towards the right hemisphere and timid fish the left. By contrast, visual laterality did not vary with personality; rather the left hemisphere was dominant across the population, as is common for fish when visually analysing unfamiliar objects. This evidence reveals differences in functional laterality between sensory systems and the role of personality in eliciting these differences. The species has a stronger input of electrical signals than visual signals in its brain; therefore, sensory representation in the brain might drive the laterality differences.

Individual differences in response to alcohol exposure in zebrafish (Danio rerio).

Personality traits are related to many aspects of one’s life, including risk taking, sociability, and behavioral changes caused by psychoactive substances. This study aimed to investigate individual differences and behavioral changes due to alcohol exposure in zebrafish (Danio rerio). To that end, adult animals were separated into two behavioral profiles: bold and shy, according to their risk taking behavior in an emergence test. Bold and shy fish were allowed to explore a 5-chamber tank and were tested for exploration and sociability (shoaling behavior) following alcohol exposure. The acute drug exposure treatments were 0.0%, 0.1% and 0.5% (v/v%) alcohol. The behavioral parameters evaluated were average and maximum swimming speed, total distance traveled, total time spent immobile, and time spent near a shoal or exploring the tank. For the groups that received no alcohol (0.0% alcohol), shy individuals spent more time near the shoal than bold fish. However, 0.5% alcohol increased bold fish responsiveness to the shoal, while both 0.1% and 0.5% alcohol diminished shoaling in shy fish. Our results show that the behavioral profiles of zebrafish are affected differently by alcohol, with shy animals seemingly more sensitive to behavioral change due to drug exposure. Moreover, we confirm zebrafish as a model for alcohol induced functional (exploration and social behavior) changes that could be useful in high throughput drug screens.