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Effect of hunger level and time of day on boldness and aggression in the zebrafish Danio rerio
Journal of Fish Biology
Abstract
The effect of two environmental variables, hunger level (fed or not fed before behavioural assays) and time of day (morning or afternoon), on the boldness and aggressiveness of male and female zebrafish Danio rerio, was tested. The results showed that neither hunger level nor time of testing influenced boldness in males and females, but hunger level significantly affected aggression in females when compared with males.
© 2015 The Fisheries Society of the British Isles.
... Lower cortisol levels, higher boldness [7] and higher locomotion [8] were found in females. However, locomotion was also found to be higher in males [9] and cortisol was unaffected by sex [8]. ...
... We hypothesized that sex influences baseline activity in zebrafish. Previous findings with this teleost found that locomotor parameters were not altered [18,19], dependent of the animaĺs age [20], increased in males [9] or increased in females [8]. Swimming time in the spinning task was not affected by sex [21]. ...
... We segregated females for 1 week and this short period did not form necrotic eggs (verified while dissecting animals under the stereoscope). In agreement with our data showing that segregation decreases female activity, Ariyomo and Watt [9] housed animals in a sex-segregated way and observed higher male locomotion, while Moretz et al. [18] used mixed-sex housing and did not find differences between sexes. In this way, our results can help explain the discrepancies of previous findings. ...
Studies with zebrafish use acclimatizing periods of at least one week immediately before the experiments. During this time, animals can be housed in sexually segregated conditions (only females or males in the tank) or in mixed-sex conditions (both sexes in the tank). The influence of sex and housing conditions regarding the presence of one or two sexes is largely unknown in zebrafish. Our aim was to evaluate the influence that sex and housing regarding the sex of animals had in the open tank task, in the inhibitory avoidance memory test, in cortisol levels and weight in zebrafish. Four groups of animals were used: 1) segregated housed females (only females were kept in the tank); 2) segregated housed males (only males were kept in the tank); 3) mixed-sex housed females (only females were analyzed from a tank containing 50% ratio of each sex); 4) mixed-sex housed males (only males were analyzed from a tank containing 50% ratio of each sex). Males showed higher total distance travelled and mean speed when compared to females. In the inhibitory avoidance memory, sexually segregated animals had higher latencies than their mixed-sex counterparts in the 1day test and sexually segregated females presented a memory that persisted longer and was able to be reinstated. Whole-body cortisol levels were higher in mixed-sex animals while weight was lower in these fish. To the best of our knowledge, this is the first time that effects of sex and housing regarding sex were investigated in behavior and physiology of zebrafish.
... These tools include molecular genetic techniques (Varshney et al. 2015;Klatt Shaw and Mokalled 2021), pharmacological methods (Agrillo and Bisazza 2014;Shams and T Gerlai 2016), and neurobiological approaches (Rinkwitz, Mourrain, and Becker 2011;Mrinalini et al. 2023). Measuring personality in zebrafish is of profound interest (Moretz, Martins, and Robison 2007;Oswald, Singer, and Robison 2013;Way et al. 2015;Christina N Toms and David J Echevarria 2014;Rey, Digka, and MacKenzie 2015;Cresci et al. 2018;Baker et al. 2018;Hamilton et al. 2021) as also is the relationship between personality and cognitive abilities (Lucon-Xiccato, Montalbano, and Bertolucci 2020; Daniel and Bhat 2020;Varma et al. 2020;Fu, Zhang, and Fan 2024;Corcoran, Storks, and Wong 2024) as well as the relationship between physiological state and personality (Araujo-Silva et al. 2018;Ariyomo and Watt 2015;Oswald, Drew, et al. 2012;Beigloo et al. 2024;Polverino et al. 2016). However most of these studies suffer from common malpractices of study design and use of statistics to measure personality like; the use of a single measurement of behavior to infer personality, using unpartitioned phenotypic associations to infer relationships with state or cognitive abilities and measuring phenotypic correlations without separating between-individual and within-individual variance components. ...
... The lack of an effect of hunger state on boldness in the Open Field test has been previously reported in zebrafish, and our results align with these findings (Ariyomo and Watt 2015). The Open Field test also demonstrates robust repeatability in zebrafish, consistent with earlier studies (H. ...
Animals adjust their behavior in response to physiological states to optimize the trade-off between energy acquisition and survival. A key question in animal personality research is whether behavioral variation is driven by consistent physiological state differences or stable personality traits. This study evaluates boldness and shoal size discrimination in adult male zebrafish (Danio rerio) across three hunger states: same-day feeding (H0), 24-hour food deprivation (H1), and 48-hour food deprivation (H2). Behavioral assessments were conducted over two testing cycles, with each individual undergoing every test twice for each hunger state within each cycle. The assays comprised the Open Field Test (OFT), Emergence Test (ET), and Social Preference Test (SPT), with the SPT conducted under binary (4 vs. 2 fish) and ternary (4 vs. 2 vs. 1 fish) choice conditions. Hunger significantly reduced emergence latency, but did not affect exploratory behavior in the OFT. Hunger also enhanced preference for larger shoals above chance in the binary SPT during the second testing cycle, though this effect was absent in ternary choices. Testing cycle effects revealed habituation-driven increases in boldness in both the tests and a progressive shift toward larger shoal preferences in the binary SPT. Among all assays, only the OFT showed significant repeatability, making it a reliable measure of boldness. However, it did not show consistent individual differences in plasticity due to hunger. These results highlight the crucial role of labile physiological states, such as hunger and habituation, in driving behavioral variation and underscore the importance of designing studies that disentangle state-dependent behaviors from stable personality traits in animal personality research.
... Perhaps more than any other consideration in the lab, how and when food is supplied can influence zebrafish aggression. For example, unfed males are more aggressive than unfed females, with little differences in aggression when all fish are well fed (Ariyomo and Watt, 2015). Furthermore, laboratory strains of zebrafish are often kept separately from one another, but when mixed together, may alter the expression of aggressive behaviors that persist for weeks (Moretz et al., 2007). ...
... Sex-linked behaviors have been reported in multiple contexts, making sex an important consideration in experimental design, but the vast majority of studies identify no significant differences in behavior between the sexes. Sex affects aggression (Ariyomo and Watt, 2015), activity levels (Conradsen and McGuigan, 2015;Tran and Gerlai, 2013), boldness (Way et al., 2015a;Dahlbom et al., 2011b), and shoaling in zebrafish (Way et al., 2015a;Ruhl et al., 2009;Engeszer et al., 2008;Ruhl and McRobert, 2005). ...
Zebrafish are an established model organism in developmental and behavioral neuroscience, also recently emerging as an excellent model to study social behavior. Zebrafish are highly social, forming groups (shoals) with structured social relationships, dominance hierarchies and overt territoriality. Moreover, social behavior in zebrafish exhibits considerable plasticity both within- (i.e., as a context-dependent behavior) and between individuals (e.g., sex-differences, personality and coping styles) of the same strain, as well as between strains. This richness and plasticity of social behavior, together with the genetic tools available to visualize and manipulate neural circuits in zebrafish places it in the forefront of studying the neurobiological mechanisms underlying complex social behavior. Here, we review the cognitive abilities involved in social behavior, as well as the different functional classes of social behavior present in zebrafish and their variation. We also highlight recent ground-breaking methodological developments in the field, including automated image-based tracking and classification of behavior coupled with video-animated social stimuli, which collectively foster the development of future high-throughput screens of zebrafish social phenotypes.
... Another factor is the current state of satiation, food-deprived individuals, even subordinates, showing higher aggressiveness (Andersson & Åhlund, 1991;Ariyomo & Watt, 2015;Lemel & Wallin, 1993). ...
Salmonid fishes are a widespread and economically important group of fishes that are strongly affected by anthropogenic environmental degradation. Consequently, studies on their behavior and ecology are essential for their conservation. Wild Arctic grayling (Thymallus arcticus) were observed in an unimpacted Alaskan river using underwater video observations for two consecutive summers (2015 and 2016). Foraging, aggressive behavior, and position held by individual fish were quantified. Fish held focal positions in the water column most of the time (mean = 81%), active foraging was observed for 14% of the observation periods, and antagonistic interactions occurred during 5% of the time. The analysis of intraspecific aggression revealed that aggressive interactions occurred between conspecifics of similar sizes (±100 mm), although the winners of bouts were significantly larger than the losers. Notably, initiators emerged as more successful in these bouts compared to receivers, irrespective of body length. These findings underscore the significance of conducting field studies to gain valuable insights into the behavior of fish in their natural stream environments.
... Hungry individuals are more likely to take risks, explore their surroundings, and exhibit aggressive behavior (Mikheev et al., 1992;Godin & Crossman, 1994;Chapman et al., 2010). An upsurge in energy demand makes the individual take adverse challenges to optimize foraging and replenish the energy needed for survival (Ariyomo & Watt, 2015). In CNTRL+D+PDTR and HGRY+D+PDTR, a perceptional shift is visible here. ...
The plasticity of behavioral traits is shaped by a complex interplay of metabolic state and extrinsic factors. All organisms including human beings are subjected to behavioral choices and complex decision-making processes. The normal mechanism underlying the behavioral choice requires flexibility in potential cost and benefit for better survival. Decisive behavior is closely linked to perception, through which organisms evaluate and interpret the available options, consciously or subconsciously, and settle on the best possible choice as the final decision. Decisions to escape from threats and approaching the prey are crucial for the survival of organisms and perception of predatory and prey stimuli influence these decisions. The predatory-prey perception is influenced by feeding state and hunger induces increased aggression and may influence decisive choice. Here zebrafish perceive small black dots as their prey and decide to approach it. In a hungry state, the perception of small dots as prey and the frequency of visits are higher than in a normal well-fed state. The zebrafish was exposed to its sympatric predator (Anabas) and showed avoidance behavior to both dots and predator in a normal state. In a hungry state, zebrafish exposed to both dots and predator, take more risks to approach the dots by avoiding predatory stimuli presented on the same side. These modulations in decisive behavior is triggered by predatory-prey perceptional shifts due to induced feeding state and the decision to take a risk in between life and a nutritional benefit is achieved by a balance between costs and benefits. Our results support, how hunger shifts behavioral decisions from avoidance to approach and thereby influences decisive behavior in zebrafish.
... In nature, factors such as environmental change and seasonal variation often result in significant spatial and temporal heterogeneity in the food available to animals, and they may suffer from starvation to different extents [13,14], which may have a strong effect on their ability to respond to predation risks [15]. Starvation has been shown to affect energy metabolism [16,17], physiology and biochemistry [18], phenotypes [19] and personality [20,21], among other factors. This suggests that fish adapt their physiological, biochemical and behavioral strategies in response to fluctuations in food abundance (e.g., reducing physical activity, decreasing levels of body energy metabolism and increasing foraging ranges) [22]. ...
Simple Summary
Anti-predator behavior is an important means for fish to avoid predator attacks. This study investigated the anti-predation strategies of qingbo (Spinibarbus sinensis) and demasone cichlid (Chindongo demasoni) in a six-arm maze with different arm types, examining both fasted and non-fasted states. We found that in the non-fasted condition, both species chose to aggregate into shoals and then enter the shelter to hide when a shelter was present in the environment, whereas, in the absence of shelter, qingbo still chose to enter the arm and demasone cichlid chose to congregate in the central area. This difference in the selection of anti-predator strategies was even more pronounced in the fasted state. This may foreshadow interspecific differences in the effect of fasting on anti-predation strategies and indicate that the availability of shelter has a non-negligible effect on this.
Abstract
In complex environments, fish often suffer from reduced physiological functioning due to starvation, which may have a significant effect on their behavioral adaptive strategies to predator attacks. We selected qingbo (Spinibarbus sinensis, which prefers flowing water habitats) and demasone cichlid (Chindongo demasoni, which prefers still water habitats), to investigate the differences in group distribution and dynamics between the two species when faced with a simulated predation attack under different trophic states (fasted for 2 weeks or fed). We chose to conduct our experiments in a six-arm maze that included a central area and six arms of equal length and width and to obtain evidence of how the fish used the various areas of the maze to respond to simulated predation attacks. We found that the two fish species differed in their responses to simulated predation attacks under different trophic states. The group structure of the two species was relatively stable, and the effect of fasting on the qingbo group was not significant, whereas the demasone cichlid group was more susceptible to the effects of fasting, shelter and a simulated predation attack. In an environment with shelter, both species had the same anti-predator strategy and tended to enter the shelter arm to hide after encountering a simulated predation attack. However, differences in the anti-predator strategies of the two species emerged in the no-shelter environment, with the qingbo tending to enter the arm to hide, whereas the demasone cichlid group chose to enter the central area to congregate, and this phenomenon was more pronounced in the fasted group. In conclusion, our research shows that even group-stable fish may shift their anti-predation strategies (i.e., entering a shelter to hide shifts to aggregating in situ into a shoal) when starved and that the worse the swimming ability of the fish, the more affected they are by starvation.
... Sex differentially influences aggression responses in zebrafish, as males, but not females, display higher aggression and whole-body cortisol when exposed to unpredictable chronic stress (Rambo et al. 2017). Hunger also affects zebrafish in a sex-specific manner, since unfed females are less aggressive (e.g., exhibit fewer nips, displays, and fast swimming) than their male counterparts in the mirror exposure test (Ariyomo and Watt 2015). While brain serotonergic activity is generally higher in subordinate zebrafish of both sexes, female fish demonstrate higher dopamine levels, but lower forebrain serotonin turnover, than males following agonistic interactions (Dahlbom et al. 2012). ...
... Sex differentially influences aggression responses in zebrafish, as males, but not females, display higher aggression and whole-body cortisol when exposed to unpredictable chronic stress (Rambo et al. 2017). Hunger also affects zebrafish in a sex-specific manner, since unfed females are less aggressive (e.g., exhibit fewer nips, displays, and fast swimming) than their male counterparts in the mirror exposure test (Ariyomo and Watt 2015). While brain serotonergic activity is generally higher in subordinate zebrafish of both sexes, female fish demonstrate higher dopamine levels, but lower forebrain serotonin turnover, than males following agonistic interactions (Dahlbom et al. 2012). ...
Zebrafish (Danio rerio) are rapidly becoming a powerful new model organism for neurobehavioral and neuropharmacological research, including translational studies of aggression. Here, we review zebrafish aggression behavioral phenotypes, as well as pharmacological and genetic models of aggression in this aquatic species, and also discuss how zebrafish models may foster future discoveries of potential therapeutic agents for reducing aggressive phenotypes.
... This latter finding likely reflects the fact that, on average, male fish tended to swim further, and explore more of the tank, than female fish. This increase in locomotor activity in male fish has been reported elsewhere (Ariyomo and Watt, 2015;Clayman et al., 2017;Philpott et al., 2012), although not universally so (Ampatzis and Dermon, 2016;Fontana et al., 2019;Rambo et al., 2017;Tran and Gerlai, 2013). We also found effects of strain, such as overrepresentation of TL fish in the shyest cluster. ...
Individual differences in exploratory behavior have been found across a range of taxa and are thought to contribute to evolutionary fitness. Animals that explore more of a novel environment and visit areas of high predation risk are considered bold, whereas animals with the opposite behavioral pattern are shy. Here, we determined whether this bimodal characterization of bold versus shy adequately captures the breadth of behavioral variation in zebrafish or if there are more than these two subtypes. To identify behavioral categories, we applied unsupervised machine to three-dimensional swim traces from over 400 adult zebrafish across four strains (AB, TL, TU, and WIK) and both sexes. We found that behavior stratified into four distinct clusters: previously described bold and shy behavior and two new behavioral types we call wall-huggers and active explorers. Clusters were stable across time and influenced by strain and sex where we found that TLs were shy, female TU fish were bold, male TU fish were active explorers, and male ABs were wall-huggers. Our work suggests that zebrafish exploratory behavior has greater complexity than previously recognized and lays the groundwork for the use of zebrafish in understanding the biological basis of individual differences in behavior.
... Although the influences of sex were not initially considered in the scope of this review, we find several differences between sexes that are worth mention. For example, various studies found that females were bolder (Dahlbom et al., 2011;Oswald et al., 2012) and less anxious (Ampatzis and Dermon, 2016;Soares et al., 2020) and aggressive (Ariyomo and Watt, 2015;Dahlbom et al., 2012) than males. Oswald et al. (2012) reported that females were bigger than males and had significantly lower levels of cortisol (Oswald et al., 2012;Rambo et al., 2017;Reolon et al., 2018;Wong et al., 2019), higher levels of blood glucose (Oswald et al., 2012) and more robust fast-start performance response (Kern et al., 2016). ...
Antagonist and long-lasting environmental manipulations (EM) have successfully induced or reduced the stress responses and quality of life of zebrafish. For instance, environmental enrichment (EE) generally reduces anxiety-related behaviours and improves immunity, while unpredictable chronic stress (UCS) and aquarium-related stressors generate the opposite effects. However, there is an absence of consistency in outcomes for some EM, such as acute exposure to stressors, social enrichment and some items of structural enrichment. Therefore, considering intraspecies variation (sex, personality, and strain), increasing intervention complexity while improving standardisation of protocols and contemplating the possibility that EE may act as a mild stressor on a spectrum between too much (UCS) and too little (standard conditions) stress intensity or stimulation, would reduce the inconsistencies of these outcomes. It would also help explore the mechanism behind stress resilience and to standardise EM protocols. Thus, this review critically analyses and compares knowledge existing over the last decade concerning environmental manipulations for zebrafish and the influences that sex, strain, and personality may have on behavioural, physiological, and fitness-related responses.
... The increased activity indicated by a faster swimming speed and acceleration rate is due to the elevated foraging motivation of starved fish (Mikheev et al., 1992). A previous study in zebrafish (Danio rerio) found that the swimming speed of starved fish was several times that of fed fish in familiar environments (Ariyomo & Watt, 2015). Consequently, faster swimming speeds and elevated activity levels increase the efficiency of exploration and hence the chances of finding food, whereas they inevitably result in longer distances between fish in starved groups compared to normally fed groups. ...
The present study aimed to reveal the effect of fasting (21 days) on collective movement and interaction dynamics in both homogeneous (eight members fed a commercial diet or deprived of food) and heterogeneous (four fed + four starved members) shoals of juvenile qingbo (Spinibarbus sinensis). The authors of this study measured the shoaling behaviour in both a commonly used rectangular open arena with no spatial complexity and a radial arm maze. When measured in the open arena, the starved shoals had a faster swimming speed and acceleration rate and a longer interindividual distance than the fed shoals, possibly because of the elevated foraging motivation. Nonetheless, the values of the heterogeneous groups were similar to those of the fed groups. Furthermore, in contrast to the fish in homogeneous shoals, the starved fish in heterogeneous shoals showed a slower acceleration rate and speed than fed members in heterogeneous shoals. These results, combined with the relationships of variables at the among‐ and within‐shoal levels, suggested that starved fish limited their motion in heterogeneous shoals to maintain group cohesion but that the fed fish contributed more to maintaining shoal structure, possibly because of the higher energy expenditure required for movement changes. When monitored in a radial arm maze, starved shoals showed more fission–fusion episodes without sacrificing group cohesion, as they adaptively adjusted the frequency and duration of each majority choice. The among‐shoal variation revealed that the heterogeneous groups showed less variation in the open arena but more variation in the radius maze than did the homogeneous groups. This difference might arise because dominant members have opposite effects on shoal behaviour and consensus decisions. In conclusion, the present study showed opposite effects of feeding states on collective behaviour between homogeneous and heterogeneous shoals, possibly because of the complicated interactions among members with different energy storage levels and foraging motivations. Furthermore, the heterogeneous groups showed a difference between shoal behaviour in the open area and exploration in the radial arm maze. Future studies manipulating the personality composition of starved and fed members of heterogeneous groups might yield interesting results.
... Personalities are often measured along different axes (e.g., bold/shy [194]; proactive/reactive [195]), and are mediated by hormones [196]. Although personality itself is influenced by intrinsic (e.g., hunger [197]) and extrinsic (e.g., environmental quality [119]) developmental factors, personality can further feedback on an individual's development through its effects on exploration [167]. For example, avoidant individuals may be less willing to investigate their environment than exploratory individuals, which reduces their chances of being predated, but also reduces foraging rate, which affects growth, as seen in grey treefrog tadpoles Hyla versicolor [198]. ...
Simple Summary
Animals must be able to solve problems to access food and avoid predators. Problem solving is not a complicated process, often relying only on animals exploring their surroundings, and being able to learn and remember information. However, not all species, populations, or even individuals, can solve problems, or can solve problems in the same way. Differences in problem-solving ability could be due to differences in how animals develop and grow, including differences in their genetics, hormones, age, and/or environmental conditions. Here, we consider how an animal’s problem-solving ability could be impacted by its development, and what future work needs to be done to understand the development of problem solving. We argue that, considering how many different factors are involved, focusing on individual animals, and individual variation, is the best way to study the development of problem solving.
Abstract
Problem solving, the act of overcoming an obstacle to obtain an incentive, has been studied in a wide variety of taxa, and is often based on simple strategies such as trial-and-error learning, instead of higher-order cognitive processes, such as insight. There are large variations in problem solving abilities between species, populations and individuals, and this variation could arise due to differences in development, and other intrinsic (genetic, neuroendocrine and aging) and extrinsic (environmental) factors. However, experimental studies investigating the ontogeny of problem solving are lacking. Here, we provide a comprehensive review of problem solving from an ontogenetic perspective. The focus is to highlight aspects of problem solving that have been overlooked in the current literature, and highlight why developmental influences of problem-solving ability are particularly important avenues for future investigation. We argue that the ultimate outcome of solving a problem is underpinned by interacting cognitive, physiological and behavioural components, all of which are affected by ontogenetic factors. We emphasise that, due to the large number of confounding ontogenetic influences, an individual-centric approach is important for a full understanding of the development of problem solving.
... Assim, como no peixe-zebra adulto, a temperatura do ambiente de teste é um fator chave na variação da resposta nociceptiva dos roedores 20,21 . Tem sido relatado que existe uma diferença entre a atividade locomotora do peixe-zebra macho e fêmea 22,23 . Como o parâmetro de nocicepção utilizado foi a atividade locomotora, foi investigado se haveria interferência do sexo do animal no comportamento nociceptivo. ...
BACKGROUND AND OBJECTIVES:
Adult zebrafish (Danio rerio) has been proposed as a low-cost and simple alternative to the use of rodents in laboratory research on novel compounds with antinociceptive potential. This study aimed to assess whether there is an influence of animal sex and the test environment on the orofacial nociceptive behavior of the adult zebrafish.
METHODS:
First, cinnamaldehyde, menthol, capsaicin, acidic saline, or glutamate was applied into the lips of the adult male or female zebrafish. Naive groups were included as control. The orofacial nociception was quantified in terms of locomotor activity. In other series of experiments, it was evaluated whether the apparatus, acclimatization, period of test, temperature of the water and color of the open field would alter the nociceptive response to cinnamaldehyde.
RESULTS:
The nociceptive behavior did not depend on the sex of the animal, apparatus, time the test was performed or the color of the open field. However, acclimatization promoted nociceptive behavior in naive animals and did not alter the nociceptive response to cinnamaldehyde (p<0.01 vs acclimatized naive). The nociception behavior was presented only when the test was performed at a temperature of 26ºC (p<0.01 vs naive).
CONCLUSION:
The results suggest the need to control the environment and water temperature as an environmental source of variation during the nociceptive behavior test of the adult zebrafish.
... Nonsignifi cant interactions were removed step-by-step (dash sign) to obtain the fi nal model. [25,26]. Hence, the food restriction of our study might explain why most of birds took the risk of going to the food. ...
... To eliminate the influence of the feeding schedule on circadian behaviour, the simplest solution is not to feed zebrafish during an experiment. This approach can only be applied for short-term experiments; long-term starvation may affect zebrafish behaviour (Ariyomo & Watt, 2015). For experiments not exceeding 2 weeks, slow-release fish food (gel or gypsum food blocks) placed at the bottom of the test aquarium could be used. ...
Over recent decades, changes in zebrafish (Danio rerio) behaviour have become popular quantitative indicators in biomedical studies. The circadian rhythms of behavioural processes in zebrafish are known to enable effective utilization of energy and resources, therefore attracting interest in zebrafish as a research model. This review covers a variety of circadian behaviours in this species, including diurnal rhythms of spawning, feeding, locomotor activity, shoaling, light/dark preference, and vertical position preference. Changes in circadian activity during zebrafish ontogeny are reviewed, including ageing‐related alterations and chemically induced variations in rhythmicity patterns. Both exogenous and endogenous sources of inter‐individual variability in zebrafish circadian behaviour are detailed. Additionally, we focus on different environmental factors with the potential to entrain circadian processes in zebrafish. This review describes two principal ways whereby diurnal behavioural rhythms can be entrained: (i) modulation of organismal physiological state, which can have masking or enhancing effects on behavioural endpoints related to endogenous circadian rhythms, and (ii) modulation of period and amplitude of the endogenous circadian rhythm due to competitive relationships between the primary and secondary zeitgebers. In addition, different peripheral oscillators in zebrafish can be entrained by diverse zeitgebers. This complicated orchestra of divergent influences may cause variability in zebrafish circadian behaviours, which should be given attention when planning behavioural studies.
... This variation may drive differences in responses related to prey cues and predator avoidance, depending on where the individual falls upon the 'bold-shy continuum' (Sih et al. 2004;Rockwell et al. 2012;Kelleher et al. 2017). Foraging functional traits are mediated by the motivational state of the individual (Nowicki et al. 2012;Ariyomo and Watt 2015). Our experimental animals were not fed prior to use, but individual variation in metabolism may drive higher foraging rates and consequently more 'risky' behavioural responses (visits to the surface) in individuals with high metabolism (Nowicki et al. 2012;Taylor and Dunn 2018). ...
Animal behavioural traits determine trophic interaction strength, which in turn structures ecological communities. Behavioural responses to prey cues can inform upon how prey are perceived and detected and therefore determine whether certain stimuli can increase or dampen predatory efficiency and therefore community structuring. We examined the functional foraging traits of an amphibian predator Xenopus laevis on mosquito larvae (Culex sp.), with regard to responses towards different prey cues. We assessed a suite of foraging behaviours exhibited when supplied with three abundances of live prey (2, 4 and 20); non-injury prey cues; prey injury kairomones from mechanically damaged prey in order to determine the importance of cues in stimulating foraging. High abundance of live prey caused frogs to visit the top of the arena significantly more than in the other treatments. This suggests that hydromechanical and visual cues alert X. laevis to prey items in different spatial zones, which results in foraging where the prey have aggregated, while the non-injury prey cue resulted in a decrease in foraging behaviours. The injury kairomone cue elicited a significantly farther distance travelled, and similar responses in terms of velocity of movement and duration of time spent moving when supplied with 20 live prey items. Previous work on X. laevis predation has focused on prey detection via lateral line sensitivity, however, the strength of response elicited by the prey injury kairomone treatment indicates that there are also complex olfactory pathways involved in detecting prey items. This is possibly related to abiotic context (i.e. turbid ponds) and high predator density in the wild.
... Traumatic brain injury (TBI) by pulsed, high-intensity focused ultrasound to the adult zebrafish brain increased shoaling cohesion (McCutcheon et al., 2017), although it may be difficult to determine the exact location and degree of brain damage caused by such a diffusive injury method. Hunger reduced aggression in females but not in males, possibly due to the females' stronger need to conserve energy compared to males (Ariyomo and Watt, 2015). ...
Social behaviors are essential for the survival and reproduction of social species. Many, if not most, neuropsychiatric disorders in humans are either associated with underlying social deficits or are accompanied by social dysfunctions. Traditionally, rodent models have been used to model these behavioral impairments. However, rodent assays are often difficult to scale up and adapt to high-throughput formats, which severely limits their use for systems-level science. In recent years, an increasing number of studies have used zebrafish (Danio rerio) as a model system to study social behavior. These studies have demonstrated clear potential in overcoming some of the limitations of rodent models. In this Review, we explore the evolutionary conservation of a subcortical social brain between teleosts and mammals as the biological basis for using zebrafish to model human social behavior disorders, while summarizing relevant experimental tools and assays. We then discuss the recent advances gleaned from zebrafish social behavior assays, the applications of these assays to studying related disorders, and the opportunities and challenges that lie ahead.
... Although different fish species exhibit unique hunger behaviour, nonetheless, it is essential at this juncture to note that, it does not vary significantly (Braithwaite et al., 2006). It was observed that the threespined sticklebacks' movement decreases as the fish is adequately fed and the motion of the school subside to a lower position (Ariyomo and Watt, 2015). It has also been reported in that hunger behavioural patterns could also be identified through circadian rhythm (Mukai et al., 2016). ...
In an automated demand feeder system, underlining the parameters that contribute to fish hunger is crucial in order to facilitate an optimised food allocation to the fish. The present investigation is carried out to classify the hunger state of Lates calcarifer. A video surveillance technique is employed for data collection. The video was taken throughout the daytime, and the fish were fed through an automated feeding system. It was demonstrated through this investigation that the use of such automated system does contribute towards a higher specific growth rate percentage of body weight as well as the total length by approximately 26.00% and 15.00%, respectively against the conventional time-based method. Sixteen features were feature engineered from the raw dataset into window sizes ranging from 0.5 min, 1.0 min, 1.5 min and 2.0 min, respectively coupled with the mean, maximum, minimum and variance for each of the distinctive temporal window sizes. In addition, the extracted features were analysed through Principal Component Analysis (PCA) for dimensionality reduction as well as PCA with varimax rotation. The data were then classified using a Support Vector Machine (SVM), k-Nearest Neighbor (k-NN) and Random Forest Tree models. It was demonstrated that the varimax based PCA yielded the highest classification accuracy with eight identified features. The prediction results based of the developed k-NN model on the selected features on the test data exhibited a classification rate of 96.5% was achieved suggesting that the features examined are non-trivial in classifying the fish hunger behaviour.
... Such behavioral differences may result from sex differences in monoaminergic activity, as females display higher dopamine but lower 5-hydroxyindolacetic acid (5-HIAA)/serotonin (5-HT) ratios than males (Dahlbom et al., 2012). Finally, hunger can also differentially affect the two sexes, as it evokes less aggression in unfed females vs. males in the mirror test (Ariyomo & Watt, 2015). ...
Sex is an important variable in biomedical research. The zebrafish (Danio rerio) is increasingly utilized as a powerful new model organism in translational neuroscience and pharmacology. Mounting evidence indicates important sex differences in zebrafish behavioral and neuropharmacological responses. Here, we discuss the role of sex in zebrafish central nervous system (CNS) models, their molecular mechanisms, recent findings and the existing challenges in this field. We also emphasize the growing utility of zebrafish models in translational neuropharmacological research of sex differences, fostering future CNS drug discovery and the search for novel sex‐specific therapies. Finally, we highlight the interplay between sex and environment in zebrafish models of sex‐environment correlations as an important strategy of CNS disease modeling using this aquatic organism.
... In addition, sex also influences aggression in zebrafish, as males, but not females, display higher aggression and whole-body cortisol when exposed to unpredictable chronic stress [119]. Hunger also affects zebrafish behavior in sex-specific manner, as unfed females are less aggressive (exhibit fewer nips, 'displays' and fast swimming) than their male counterparts in the mirror test [120]. Such sex differences may be related to variance in zebrafish monoaminergic activity and 'personality' of individual animals. ...
The zebrafish (Danio rerio) is increasingly utilized as a powerful new model organism in neurobehavioral research. Aggression is a common symptom of many CNS disorders, has some genetic determinants and can be modulated pharmacologically in humans and animal model species. Mounting evidence suggests zebrafish as a useful tool to study neurobiology of aggression, and its pharmacological and genetic regulation. Here, we discuss mechanisms of zebrafish aggression and their pharmacological, pharmacogenetic and pharmacogenomic models, as well as recent developments and existing challenges in this field. We also emphasize the growing utility of zebrafish models in translational neuropharmacological research of aggression, fostering future discoveries of potential therapeutic agents for aggressive behavior.
... Knowledge about these behavioral patterns, as well as physiological studies of fish under entrained feeding are essential to develop feeding protocols in candidate fish (Lazado et al., 2017). In this sense, there is increasing interest in studies that consider feeding rhythms, circadian variation and environmental variables (Ariyomo and Watt, 2015;Lazado et al., 2017). Recent research has started to unravel the pathways that underlie feeding regulation, including meal-related circadian variation using self-feeding systems in arapaima (Mattos et al., 2016a(Mattos et al., , 2016b. ...
... Similarly, Barramundi apart from being term as the Asian sea bass depicts favourable results when they adjust the lights to imitate the night and day situations [8]. Razor fish or Xyrithchys novacula the zebrafish or Danio rerio were the other common species that has undergone similar practices in identifying the patters where the genders and resting time were evaluated as a part of circadian rhythm studies [9,10]. ...
Fish Hunger behaviour is essential in determining the fish feeding routine, particularly for fish farmers. The inability to provide accurate feeding routines (under-feeding or over-feeding) may lead to the death of the fish and consequently inhibits the quantity of the fish produced. Moreover, the excessive food that is not consumed by the fish will be dissolved in the water and accordingly reduce the water quality through the reduction of oxygen quantity. This problem also leads to the death of the fish or even spur fish diseases. In the present study, a correlation of Barramundi fish-school behaviour with hunger condition through the hybrid data integration of image processing technique is established. The behaviour is clustered with respect to the position of the school size as well as the school density of the fish before feeding, during feeding and after feeding. The clustered fish behaviour is then classified through k-Nearest Neighbour (k-NN) learning algorithm. Three different variations of the algorithm namely, fine, medium and coarse are assessed on its ability to classify the aforementioned fish hunger behaviour. It was found from the study that the fine k-NN variation provides the best classification with an accuracy of 88%. Therefore, it could be concluded that the proposed integration technique may assist fish farmers in ascertaining fish feeding routine.
... To avoid disturbances, no human was present during recordings and tanks were covered with black plastic foil on three sides. Individuals were tested at the same time of day ± 15 min to avoid potential effects of hunger level or time of day on individual aggression [44,45] in repeated trials. ...
Although personality traits can largely affect individual fitness we know little about the evolutionary forces generating and maintaining personality variation. Here, we investigated the hypothesis that personality variation in aggression is sexually selected in the monogamous, bi-parental cichlid Pelvicachromis pulcher. In this species, breeding pairs form territories and they aggressively defend their territory and offspring against con- and heterospecific intruders. In our mate choice study, we followed up two alternative hypotheses. We either expected females to show a directional preference for a high level and high consistency of aggression (potentially indicating mate choice for male parental quality). Alternatively, we expected females to choose males for (dis-)similarity in the level/consistency of aggression (potentially indicating mate choice for compatibility). Individual level and consistency of aggression were assessed for males and females using mirror tests. After eavesdropping on aggressive behaviour of two males (differing in level and consistency of aggression) females were then allowed to choose between the two males. Males, but not females, showed personality variation in aggression. Further, females generally preferred consistent over inconsistent males independent of their level of aggression. We did not detect a general preference for the level of male aggression. However, we found an above average preference for consistent high-aggression males; whereas female preference for inconsistent high-aggression did not deviate from random choice. Our results suggest behavioural consistency of aggression in male rainbow kribs is selected for via female mate choice. Further, our study underlines the importance of considering both the level and the consistency of a behavioural trait in studies of animal behaviour.
... For instance, the growth rate of the fish in correlation to light sensitivity was investigated [8]. The resting time, as well as the active motion between genders of zebrafish or Danio rerio and razor fish or Xyrithchys novacula with relation to feeding state, has also been investigated [9][10]. Several classification techniques have been employed due to its superiority against conventional statistical concept [11][12]. ...
Fish Hunger behaviour is essential in determining the fish feeding routine, particularly for fish farmers. The inability to provide accurate feeding routines (under-feeding or over-feeding) may lead the death of the fish and consequently inhibits the quantity of the fish produced. Moreover, the excessive food that is not consumed by the fish will be dissolved in the water and accordingly reduce the water quality through the reduction of oxygen quantity. This problem also leads the death of the fish or even spur fish diseases. In the present study, a correlation of Barramundi fish-school behaviour with hunger condition through the hybrid data integration of image processing technique is established. The behaviour is clustered with respect to the position of the school size as well as the school density of the fish before feeding, during feeding and after feeding. The clustered fish behaviour is then classified through k-Nearest Neighbour (k-NN) learning algorithm. Three different variations of the algorithm namely cosine, cubic and weighted are assessed on its ability to classify the aforementioned fish hunger behaviour. It was found from the study that the weighted k-NN variation provides the best classification with an accuracy of 86.5%. Therefore, it could be concluded that the proposed integration technique may assist fish farmers in ascertaining fish feeding routine.
... Barramundi which is often referred to as the Asian sea bass has shown as a practical specimen for collecting data, where a study conducted has evaluated the growth rate of the fish where the day and night moment are manipulated [8]. Other common species that have been examined are the zebrafish or Danio rerio and razor fish or Xyrithchys novacula in which the boldness between genders during hunger and circadian rhythms for resting time and active state, respectively are examined [9][10]. The latter study also demonstrates the implementation of using acoustic tracker to evaluate the motion of the fishes by means of hidden Markov models. ...
Fish Hunger behaviour is one of the important element in determining the fish feeding routine, especially for farmed fishes. Inaccurate feeding routines (under-feeding or over-feeding) lead the fishes to die and thus, reduces the total production of fishes. The excessive food which is not eaten by fish will be dissolved in the water and thus, reduce the water quality (oxygen quantity in the water will be reduced). The reduction of oxygen (water quality) leads the fish to die and in some cases, may lead to fish diseases. This study correlates Barramundi fish-school behaviour with hunger condition through the hybrid data integration of image processing technique. The behaviour is clustered with respect to the position of the centre of gravity of the school of fish prior feeding, during feeding and after feeding. The clustered fish behaviour is then classified by means of a machine learning technique namely Support vector machine (SVM). It has been shown from the study that the Fine Gaussian variation of SVM is able to provide a reasonably accurate classification of fish feeding behaviour with a classification accuracy of 79.7%. The proposed integration technique may increase the usefulness of the captured data and thus better differentiates the various behaviour of farmed fishes.
... We demonstrated that mirror-induced aggression is a visually-based behaviour (Fig. 3a,b) that does not alter depending upon the time of day (Fig. 3c,d) or month of the year (Fig. 3e,f). The finding that aggression does not show circadian alterations agrees with a previous study that compared zebrafish agonistic behaviour between 9-11 am and 2-4 pm (Ariyomo and Watt, 2015). This suggests that aggression can be compared in the morning and afternoon, thereby increasing the number of animals that can be measured in one day. ...
Background:
Although aggression is a common symptom of psychiatric disorders the drugs available to treat it are non-specific and can have unwanted side effects. The zebrafish is an ideal model for aggression research. Zebrafish are small, amenable to genetic and pharmacological manipulation, and agonistic behaviour can be measured reliably.
New method:
In this study we have established a novel setup to automatically quantify aggression and locomotion in one-month old juvenile zebrafish, a stage at which fish exhibit adult-like behaviour but are small that one camera can film several animals.
Results:
We have validated our novel software by comparison to manual quantification of behaviour, characterised the aggression of one-month old fish, and demonstrated that we can detect alterations to aggression caused by mutation or drug application.
Comparison with other methods:
The ability to record up to 12 juvenile fish allows us to speed up and standardise data acquisition compared to studies of single fish.
Conclusions:
This setup appears to be suitable to screen for drugs that decrease zebrafish aggression as a first step toward developing novel treatments for this behaviour.
... Boldness in an individual is increased by temperature and motivational state (Stephens & Krebs, 1986;Cuthill & Houston, 1997;van Baalen et al., 2001;Nowicki et al., 2012). When hungry, fishes exhibit enhanced boldness due to an augmented motivational state; this causes them to become more vulnerable to predators and less selective toward prey until threshold fullness is satisfied (Ariyomo & Watt, 2015). This could be an underlying mechanism in the results, in that an increased motivational state in the experimental setting could explain the type II response at 15 and 17 ∘ C and the transition into a type III sigmoidal response at 19 ∘ C may indicate a thermal threshold. ...
Interactions between Lipophrys pholis and its amphipod prey Echinogammarus marinus were used to investigate the effect of changing water temperatures, comparing current and predicted mean summer temperatures. Contrary to expectations, predator attack rates significantly decreased with increasing temperature. Handling times were significantly longer at 19° C than at 17 and 15° C and the maximum feeding estimate was significantly lower at 19° C than at 17° C. Functional-response type changed from a destabilizing type II to the more stabilizing type III with a temperature increase to 19° C. This suggests that a temperature increase can mediate refuge for prey at low densities. Predatory pressure by teleosts may be dampened by a large increase in temperature (here from 15 to 19° C), but a short-term and smaller temperature increase (to 17° C) may increase destabilizing resource consumption due to high maximum feeding rates; this has implications for the stability of important intertidal ecosystems during warming events.
... Juvenile lesser-spotted dogfish have almost double the metabolism rate of adult specimens (Sims 1996), so despite the short trial time, the predator may experience more motivational states during the raised temperature treatments due to the increased rate of digestion. This may alter searching behaviour at high prey densities (Clark and Mangel 2000;Ariyomo and Watt 2015). The behaviours that make up handling time are considered to be composite of a multitude of processes including; subduing, chewing, swallowing, digestion and gut evacuation, all of which are controlled by physiological processes that are affected in different manners by increasing temperatures (Jeschke et al. 2002). ...
Predation is a strong driver of population dynamics and community structure and it is essential to reliably quantify and predict predation impacts on prey populations in a changing thermal landscape. Here, we used comparative functional response analyses to assess how predator-prey interactions between dogfish and invertebrate prey change under different warming scenarios. The Functional Response Type, attack rate, handling time and maximum feeding rate estimates were calculated for Scyliorhinus canicula preying upon Echinogammarus marinus under temperatures of 11.3 °C and 16.3 °C, which represent both the potential daily variation and predicted higher summer temperatures within Strangford Lough, N. Ireland. A two x two design of “Predator Acclimated”, “Prey Acclimated”, “Both Acclimated”, and “Both Unacclimated” was implemented to test functional responses to temperature rise. Attack rate was higher at 11.3 °C than at 16.3 °C, but handling time was lower and maximum feeding rates were higher at 16.3 °C. Non-acclimated predators had similar maximum feeding rate towards non-acclimated and acclimated prey, whereas acclimated predators had significantly higher maximum feeding rates towards acclimated prey as compared to non-acclimated prey. Results suggests that the predator attack rate is decreased by increasing temperature but when both predator and prey are acclimated the shorter handling times considerably increase predator impact. The functional response of the fish changed from Type II to Type III with an increase in temperature, except when only the prey were acclimated. This change from population destabilizing Type II to more stabilizing Type III could confer protection to prey at low densities but increase the maximum feeding rate by Scyliorhinus canicula in the future. However, predator movement between different thermal regimes may maintain a Type II response, albeit with a lower maximum feeding rate. This has implications for the way the increasing population Scyliorhinus canicula in the Irish Sea may exploit valuable fisheries stocks in the future.
... Predators were able to turn around in their cylinder and did not show any distressed behaviour. For each treatment, individual fish were tested at the same time of day (±30 min) to control for any potential effects of hunger level and time of day on individual behaviour (Ariyomo & Watt, 2015;MacPhail et al., 2009). A complete water change of experimental aquaria was performed after every three trials. ...
Virtual stimuli represent an increasingly popular tool in the study of animal behaviour. Modern techniques have the potential to simplify and improve traditional experiments using live stimuli. However, the increasing availability of diverse techniques is associated with problems and limitations. Although many new methods have been developed, their validation remains largely untested. In the present study, we therefore performed two experiments to test whether 2-D animations of predators and conspecifics elicit biologically appropriate behavioural responses in male rainbow kribs, Pelvicachromis pulcher. Individual responses towards a sympatric natural fish predator, Parachanna obscura, were tested using live predators and still colour photographs, animated using PowerPoint©. Compared to control trials (empty aquarium and white computer screen, respectively), individuals decreased their activity in response to both live and animated predators. We found no difference in activity between live and animation trials. Further, we tested individual aggression (frequency of aggressive behaviours) exhibited towards live and animated conspecifics. Individual aggressive behaviours shown towards live and animated conspecifics were positively correlated. Moreover, an individual's mean distance towards the opponent was a suitable proxy for individual aggression permitting the facilitation and standardisation of an individual's aggression through the use of a tracking software compared with the more laborious, traditional manual assessment. Our results show that simple, inexpensive animation techniques have the potential to provide an easy-to-apply and useful technological advance in animal behaviour research.
... Trials were video-recorded from above with no human present during trials and the test tank was surrounded with white Plexiglas to avoid disturbances. Individuals were always boldness-typed at the same time of day ± 30 min to account for potential effects of time of day and hunger level on individual activity pattern (Ariyomo & Watt, 2015;MacPhail et al., 2009). In each boldness test, individuals were exposed to a randomly chosen animation showing a predator specimen they had not seen before. ...
Although the existence of consistent between-individual differences in behaviour (‘personality differences’) has been well documented during the last decade, the adaptive value of such behavioural limitations remains an open field for researchers of animal behaviour. Personalities clearly restrict individuals in their ability to adjust their behaviour to different conditions. However, sheer costs of flexibility cannot explain the polymorphism created by personality variation. In a correlative approach, we here tested whether mate choice might act as a major driving force maintaining personality variation in the monogamous, biparental rainbow krib, Pelvicachromis pulcher. We personality-typed all males and females for their boldness (activity under simulated predation risk) and allowed females to choose between two males that differed in their boldness (behavioural level and consistency). Prior to the choice, females were allowed to observe both males, expressing their natural boldness towards a video-animated natural predator. Both sexes showed personality differences in boldness over the short and long term. Furthermore, when removing side-biased females, we found a disassortative mating preference for the behavioural level and an assortative preference for behavioural consistency in boldness. These preference patterns might facilitate effective parental role allocation during offspring care and/or provide genetic benefits. Our results suggest that sexual selection plays an important role in the evolution of personality differences.
... After 60 s of fish introduction in the aquaria, aggressive interactions (bites, displays and fast bouts of swimming) were recorded for a period of 5 min. This protocol has been previously validated by actual fish opponents (Ariyomo et al., 2013;Ariyomo and Watt, 2015). Aggressive behavior (boldness and aggressiveness) in zebrafish can be influenced be genetic background (Ariyomo et al., 2013), but aggressiveness was similar between male and female zebrafish (Dahlbom et al., 2011), indicating the appropriateness of using both sexes. ...
... A number experimental parameters influence zebrafish aggression including genes, neurotransmitters, and hormones as well as social interactions, hunger levels, and environmental conditions during embryonic development [Marks et al., 2005;Moretz et al., 2007b;Norton et al., 2011;Ariyomo et al., 2013;Ariyomo and Watt, 2015]. For example, the level of aggression is lower in a complex habitat than in a simple one [Basquill and Grant, 1998]. ...
Aggression is an adaptive behavioral trait that is important for the establishment of social hierarchies and competition for mating partners, food, and territories. While a certain level of aggression can be beneficial for the survival of an individual or species, abnormal aggression levels can be detrimental. Abnormal aggression is commonly found in human patients with psychiatric disorders. The predisposition to aggression is influenced by a combination of environmental and genetic factors and a large number of genes have been associated with aggression in both human and animal studies. In this review, we compare and contrast aggression studies in zebrafish and mouse. We present gene ontology and pathway analyses of genes linked to aggression and discuss the molecular pathways that underpin agonistic behavior in these species. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
... They are less aggressive in still water or fast flowing streams (Suriyampola et al., 2016). Aggression levels are also influenced by internal states such as hunger (Ariyomo and Watt, 2015) and external parameters including the presence of vegetation (Basquill and Grant, 1997), oxygen levels in the environment (Ivy et al., 2017;Marks et al., 2005) or the release of conspecific alarm substance . The stress level of an animal can also alter this behaviour (Summers and Winberg, 2006). ...
Aggression is an important adaptive behavior that can be used to monopolize resources such as mates or food, acquire and defend territory and establish dominant hierarchies in social groups. It is also a symptom of several psychiatric disorders including attention-deficit/hyperactivity disorder and schizophrenia. The frequent comorbidity of aggression and psychiatric diseases suggests that common genes and neural circuits may link these disorders. Research using animal models has the potential to uncover these genes and neural circuits despite the difficulty of fully modeling human behavioral disorders. In this review we propose that zebrafish may be a suitable model organism for aggression research with the potential to shed light upon the aggressive symptoms of human diseases.
This study examined the impact of tank color (black, red, blue, green, and transparent) on the behavior (boldness and aggressiveness) and growth of Nile Tilapia over nine weeks (first, third, sixth, and ninth weeks). Boldness and aggression levels were assessed using open field and mirror image tests, respectively, for individual Nile Tilapia (Oreochromis niloticus). Healthy Nile Tilapia, initially weighing 2.51g on average, were used in the experimental trials conducted in tanks of different colors. The findings indicated that red tanks appeared to foster the highest level of boldness (p<0.05), whereas fish in transparent tanks exhibited the highest level of aggressiveness compared to other tanks (p<0.05). Moreover, individuals in black tanks displayed the highest growth rate in terms of weight (p<0.05). This study suggests that Oreochromis niloticus can thrive better in black-rearing tanks, as the black tanks appear to enhance the growth rate of the fish, possibly through improvements in physiological processes.
Consistent individual differences in exploratory behavior have been found across a range of taxa, including zebrafish, and are thought to contribute to evolutionary fitness. Animals that explore more of a novel environment, and visit areas of high predation risk, are considered bold, whereas animals with the opposite pattern of behavior are considered shy. Here, we examined whether this bimodal characterization of bold versus shy adequately captures the breadth of exploratory behavior exhibited by zebrafish or if their behavior falls into several distinct behavioral subtypes instead. To identify the presence of behavioral subtypes, we used unsupervised machine learning applied to exploratory behaviors extracted from three-dimensional swim traces from over 400 adult zebrafish across four strains (AB, TL, TU, and WIK) and both sexes and found that their exploratory behavior stratified into four distinct clusters. These included previously described bold and shy behavior as well as two new behavioral types: wall-huggers and active explorers. Consistent with prior descriptions of individual differences, these behavioral subtypes were stable across days and influenced by the strain and sex of the animals. Taken together, our work suggests that zebrafish behavior exhibits greater complexity than is typically assumed.
The notion that men are more variable than women has become embedded into scientific thinking. For mental traits like personality, greater male variability has been partly attributed to biology, underpinned by claims that there is generally greater variation among males than females in non-human animals due to stronger sexual selection on males. However, evidence for greater male variability is limited to morphological traits, and there is little information regarding sex differences in personality-like behaviours for non-human animals. Here, we meta-analysed sex differences in means and variances for over 2100 effects (204 studies) from 220 species (covering five broad taxonomic groups) across five personality traits: boldness, aggression, activity, sociality and exploration. We also tested if sexual size dimorphism, a proxy for sex-specific sexual selection, explains variation in the magnitude of sex differences in personality. We found no significant differences in personality between the sexes. In addition, sexual size dimorphism did not explain variation in the magnitude of the observed sex differences in the mean or variance in personality for any taxonomic group. In sum, we find no evidence for widespread sex differences in variability in non-human animal personality.
The aging process of reservoirs has been extensively investigated; however, little is known about how fish populations are adjusted after many years of impoundment. Thus, this study aimed to compare the diet, length-weight relationship, sizes classes, variation in size, and age of Astyanax lacustris Lütken, 1875 collected from lotic and lentic habitats of an aging reservoir. The study group consisted of 730 captured fishes. We found that specimens collected from lotic habitats had a wider range of size classes (1.0 to 12.0 cm), were linked to a high frequency of juveniles (48.7%), and had greater feeding activity (higher stomach fullness). In contrast, fishes collected from lentic environments exhibited high rates of capture (78.4%), increased frequency of adults (87.3%), and higher values of mean standard length. The length-weight relationship indicated that lentic fishes were heavier than fish collected from lotic areas. Moreover, we observed 37 food items in A. lacustris diet, mainly plant material, algae, Cladocera, Hymenoptera, Coleoptera, and Ephemeroptera. Differences among the diet of fishes between sites were evidenced with Permanova (p < 0.05). Astyanax lacustris can be considered a persistent species in Chavantes Reservoir after aging, encountering conditions to complete its life span and adjusting to food resources.
Each fish unknowingly possesses systems for recording a number of its vital activities and behaviors from embryonic life to death. Its “past” is revealed, on the one hand by its otoliths, on the other hand, by its parasites. The otolith can be used to measure the age of the larvae, based on a hatching mark, and to assess the duration of their marine migration. The behavioral abilities of fish have often been related to the size of their brain, particularly that of their telencephalic optical roof, which varies according to environmental and social factors. The social behavior of an adult fish may depend on the social environment in which it developed and the social interactions it experienced early in its young years. Fish, like all living creatures, know how to synchronize their vital feeding, migratory, social, reproductive and other activities with the natural cyclical variations of their environment.
This chapter highlights the findings of the developmental monitoring systems for swimming pattern or motion analysis with regard to feeding behaviour. A benchmark for examining the framework on how scientists control fish in animal variable function factors was gathered and referred to gauge the adequate design in constructing a viable device. The validation of image processing and automated demand feeder to determine the results will also be considered, as a validation aspect between the system of tracking and the behaviour of the Lates calcarifer where the pixel intensity will be extracted as the features. The results of this chapter will enable the reader on the development of an integrated feeder scheme that consolidates surveillance scheme to identify the feeding behaviour and relation towards the specific growth rate (SGR).KeywordsImage processingAutomated demand feeder
Lates calcarifer
Pixel intensitySpecific growth rate
This book highlights the fundamental association between aquaculture and engineering in classifying fish hunger behaviour by means of machine learning techniques. Understanding the underlying factors that affect fish growth is essential, since they have implications for higher productivity in fish farms. Computer vision and machine learning techniques make it possible to quantify the subjective perception of hunger behaviour and so allow food to be provided as necessary. The book analyses the conceptual framework of motion tracking, feeding schedule and prediction classifiers in order to classify the hunger state, and proposes a system comprising an automated feeder system, image-processing module, as well as machine learning classifiers. Furthermore, the system substitutes conventional, complex modelling techniques with a robust, artificial intelligence approach. The findings presented are of interest to researchers, fish farmers, and aquaculture technologist wanting to gain insights into the productivity of fish and fish behaviour.
Theory predicts that staying in a refuge has benefits in terms of predator avoidance and costs in terms of lost feeding opportunities. In this study, we investigated how the relative importance of these costs and benefits changes with increasing body length. This is of particular interest in animals such as fish, which show continuous growth throughout their lives. Our results suggest that larger fish are subject to lower predation risks and are less affected by food deprivation than small fish, with fish decreasing their responses to food-deprivation treatments more strongly with increasing body length than to predation treatments. This may explain our observation that large fish emerged later from a refuge than small ones and spent shorter times outside the refuge. The key role of differential responses to food deprivation was further illustrated by the finding that the relative weight loss of individual fish was strongly correlated with a reduction in hiding time even in the absence of body length differences. The importance of inter-individual differences in metabolic rates for the decision-making behaviour of animals is discussed.
The behavioural patterns and their cireadian rhythms may be adaptive to the peculiar environmental conditions of subtropical brackish waters where Ba-thygobius soporator Valenciennes, 1837 live. Adult fish were caught at the southern Brazilian coast from mangrove rivers and rocky shores in a bay, where temperature and water salinity vary during the day and through the year. Observation on the behaviour of the animals was undertaken in salinity 8.5ppt, 17.0ppt, 25.5ppt and 34.0ppt, each one in temperatures of 18ºC and 28ºC. Temperature and salinity affect the frequency and intensity of some of the behavioural events, more than its pattern or rhythm. Swimming is rare, decreasing along the day and with temperature increase, being even lower at low salinity; aggressiveness is the highest in the morning being not affected by temperature, but by salinity, being higher the higher it is; territory defence decreases along the day and is lower at high temperature and extreme salinities; fish hide more at high temperature and with the decrease of salinity, but this is not rhythmical; a higher proportion of fish rest in vertical position when salinity and temperature are high, increasing slightly at the beginning of the afternoon; respiratory frequency increases with temperature, salinity and in the afternoon; the colour of the fish is mainly light with spots in all hours of the day and in all temperatures and different levels of salinity, but with a tendency of the presence of some dark fish during the morning and some light ones in the afternoon, showing a higher variability of colours at low temperature and extreme salinities. Besides temperature, salinity and light, feeding seems to be one of the determinant factors for the performance of the typical behaviour of B. soporator.
Refuge use by animals provides greater safety from predation. A refuging animal continuously must decide whether to stay in the refuge or to emerge into open habitat. This decision may depend on its energetic state and vulnerability to predation, both of which can vary with individual body size. We experimentally tested the concurrent effects of body size and nutritional (hunger) state on refuge use in the banded killifish (Fundulus diaphanus). Individual killifish were "attacked" in an open laboratory habitat (containing food) by either a trout predator model or a control model that did not resemble a trout. Frightened fish typically fled into a foodless refuge nearby. The amount of time that killifish spent in the refuge before emerging increased significantly with body length, but was not affected by their current nutritional state or the threatening stimulus (type of model). Smaller killifish were thus more risk-prone than larger conspecifics irrespective of their current nutritional state. Such size-mediated risk-taking behaviour has important consequences for individual fitness and implications for population and community composition and dynamics in nature.
Behavioral variation has been documented both between and within populations in a variety of traits. Many of these behavioral traits are phenotypically plastic and are conditional on the early environment an animal experiences, yet despite this the role of the environment in generating variation in boldness is not well understood. Here we investigate the importance of early and recent experience of temporal unpredictability in food supply on the behavior of a species of freshwater fish, the Trinidadian guppy Poecilia reticulata. We predict that individuals that experience temporally unpredictable food supplies will engage in more risky behavior than those experiencing a predictable food supply and find evidence to support this. Fish with early experience of unpredictable environments are generally bolder and more exploratory than fish reared in predictable environments, exploring a significantly greater proportion of a novel maze and spending less time in a refuge during the trial. Individuals with early experience of unpredictability also spent significantly less time associating with conspecifics in a shoaling tendency assay, again suggesting that they are bolder than guppies reared in predictable conditions. These findings suggest that early experience is important in shaping exploratory and shoaling behavior in this species and that unpredictability in early life can influence boldness in guppies. Key words: boldness, exploration, phenotypic plasticity, shoaling, unpredictable environment. [Behav Ecol 21:501–506 (2010)]
Juvenile Atlantic salmon Salmo salar were shown experimentally to make adaptive behavioural decisions as a short-term response to changes in food availability and predation risk. Restricted food availability caused an increase in activity, whereas activity was decreased under predation threat. Although changes in activity were not more pronounced among the hunger-motivated fish, suggesting that they were not balancing risk and hunger, hungrier fish spent less time in refuges in the presence of a predator, indicating that they were more willing to take risks than satiated fish. Aggressive interactions among juvenile Atlantic salmon were decreased by predation threat, but were highest when predators were absent and food was abundant.
Personality differences are a widespread phenomenon throughout the animal kingdom. Past research has focused on the characterization of such differences and a quest for their proximate and ultimate causation. However, the consequences of these differences for ecology and evolution received much less attention. Here, we strive to fill this gap by providing a comprehensive inventory of the potential implications of personality differences, ranging from population growth and persistence to species interactions and community dynamics, and covering issues such as social evolution, the speed of evolution, evolvability, and speciation. The emerging picture strongly suggests that personality differences matter for ecological and evolutionary processes (and their interaction) and, thus, should be considered a key dimension of ecologically and evolutionarily relevant intraspecific variation.
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.
Individual humans, and members of diverse other species, show consistent differences in aggressiveness, shyness, sociability and activity. Such intraspecific differences in behaviour have been widely assumed to be non-adaptive variation surrounding (possibly) adaptive population-average behaviour. Nevertheless, in keeping with recent calls to apply Darwinian reasoning to ever-finer scales of biological variation, we sketch the fundamentals of an adaptive theory of consistent individual differences in behaviour. Our thesis is based on the notion that such ‘personality differences’ can be selected for if fitness payoffs are dependent on both the frequencies with which competing strategies are played and an individual's behavioural history. To this end, we review existing models that illustrate this and propose a game theoretic approach to analyzing personality differences that is both dynamic and state-dependent. Our motivation is to provide insights into the evolution and maintenance of an apparently common animal trait: personality, which has far reaching ecological and evolutionary implications.
Both hunger and body size differences increase the likelihood that an encounter between 2 predators turns into a cannibalistic event. Two hypotheses with opposite predictions can be proposed to explain how hunger influences cannibalism. The first claims that starvation weakens individuals, which then fall victim more easily to conspecifics that are more successful foragers or in better condition. The other suggests that starvation increases aggressiveness and willingness to take risks, so that starved individuals might more often become cannibals. We staged encounters between pairs of wolf spiders (Pardosa prativaga) of different body mass ratios, where either one was satiated and the other was starved or both were satiated. In 2 experiments, we found that in encounters between a hungry and a satiated spider of the same mass, the hungry spider was most often the cannibal. We also found an interaction between hunger asymmetry and body mass asymmetry in the likelihood of cannibalism occurring and the time taken until the cannibalistic event. These results support the second hypothesis that predicts that success in cannibalism will result from increased aggression and risk taking induced by hunger. Our results have implications for the consequences of cannibalism at population and community levels because they assign an increased emphasis on intracohort cannibalism resulting from food limitation. Copyright 2010, Oxford University Press.
Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (101–103 ind1–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches.
Consistent differences in human behaviour are often explained with reference to personality traits. Recent evidence suggests
that similar traits are widespread across the entire animal kingdom and that they may have substantial fitness consequences.
One of the major components of personality is the shyness–boldness continuum. Little is known about the relative contributions
of genes and the environment in the development of boldness in wild animal populations. Here, we bred wild-caught fish (Brachyraphis episcopi) collected from regions of high- and low-predation pressure, reared their offspring in the laboratory under varying conditions
and tested boldness utilising an open-field paradigm. First-generation laboratory-reared fish showed similar behaviour to
their wild parents suggesting that boldness has a heritable component. In addition, repeated chasing with a net increased
boldness in both high- and low-predation offspring, showing that boldness is also heavily influenced by life experiences.
Differences between males and females were also sustained in the laboratory-reared generation indicating that sex differences
in boldness are also heritable. We discuss these results with reference to the potential underlying genetic and hormonal mechanisms
as well as the environmental influences that may be responsible for expression of boldness in wild animals.
Predator evasion behaviour patterns of three populations of rainbowfish (Melanotaenia eachamensis) were compared. The populations differed in the level of complexity of their natural habitats and the type and extent of
predation. The predator recognition abilities of fish were assessed by exposing them to models differing in their degree of
predator realism. The availability of vegetated cover and the location of the models with respect to cover were manipulated.
Fish from Lake Tinaroo, a relatively open habitat containing numerous predators, showed strong changes in elective group size
(EGS) in response to the different models but did not rely on cover as a place of refuge. In contrast, Dirran Creek fish originate
from a small, fast-flowing, structurally complex stream lacking predatory fish species, and they showed little ability to
distinguish between the different models and responded to threat by spending longer in vegetated areas. Members of the Lake
Eacham captive stock increased their EGS in response to models representing low threat and with more threatening models increased
the amount of time spent in vegetated regions of the arena. The contrasting reactions to predatory threat displayed by these
populations highlights the need to use a number of different response indices when comparing the anti-predator responses of
different fish populations. These data suggest that the level of habitat complexity as well as prior predator experience influence
anti-predator responses of different fish popu-lations.
The food-amount hypothesis, proposed to account for sibling aggression in brood-reducing bird species, predicts that broods will be aggressive when hungry, and that as a result, senior siblings will be able to take a greater share of the total available food. We performed a field experiment to test these predictions in ospreys, Pandion haliaetus. Broods were removed from their natal nests and subjected to a series of experimental trials. Each trial consisted of a 3.5-h starvation period followed by a feeding or sham-feeding treatment designed to manipulate the hunger of the nestlings. Following treatment, broods were placed in a viewing nest along with a fish. While the viewing-nest mother fed the fish to the brood, we recorded food allocation and aggresssion. Each of 10 broods experienced a number (one to six) of feeding and sham-feeding treatments over a period of 2 days and was then returned to its natal nest. Broods were slightly but significantly more aggressive after sham-feeding treatments, and senior siblings took a greater share of the meal. The tremendous variation in the level of sibling aggression observed between broods was inversely related to brood mass asymmetry but not to condition, suggesting that siblings adjusted the rate of aggression according to the level of competition within their broods.
Behavioral syndromes are suites of two or more behaviors that correlate across environmental contexts. The aggression-boldness syndrome links aggression, boldness, and exploratory activity in a novel environment. Although aggression-boldness has been described in many animals, the mechanism linking its behavioral components is not known. Here we show that mutation of the gene encoding fibroblast growth factor receptor 1a (fgfr1a) simultaneously increases aggression, boldness, and exploration in adult zebrafish. We demonstrate that altered Fgf signaling also results in reduced brain histamine levels in mutants. Pharmacological increase of histamine signaling is sufficient to rescue the behavioral phenotype of fgfr1a mutants. Together, we show that a single genetic locus can underlie the aggression-boldness behavioral syndrome. We also identify one of the neurotransmitter pathways that may mediate clustering of these behaviors.
Author Summary
The circadian clock is a physiological timing mechanism that allows organisms to anticipate and adapt to the day-night cycle. Since it ticks with a period that is not precisely 24 h, it is vital that it is reset on a daily basis by signals such as light to ensure that it remains synchronized with the day-night cycle. The molecular mechanisms whereby light regulates the clock remain incompletely understood. Here we have studied a cavefish that has evolved for millions of years in the perpetual darkness of subterranean caves in Somalia. Like many other cave animals, these fish display striking adaptations to their extreme environment, including complete eye degeneration. We show that despite evolving in a constant environment, this blind cavefish still retains a circadian clock. However, this clock ticks with an extremely long period (nearly 47 h), and importantly it does not respond to light. We reveal that eye loss does not account for this “blind” clock. Specifically, mutations of two widely expressed non-visual opsin photoreceptors (Melanopsin and TMT opsin) are responsible for the blind clock phenotype in the cavefish. Our work illustrates the great utility of cavefish for studying the evolution and regulation of the circadian clock.
The zebrafish has considerable potential for use as a model in the study of behavior in social systems, particularly dominance hierarchies, which are widespread in nature and can affect the lifelong success of individuals. There is, however, a paucity of information relating to the characterization of social groups and significance of dominance hierarchies in the zebrafish model. This study set out to bridge this knowledge gap and better characterize dominance and its implications for reproductive success in both male and female zebrafish in colonies comprising of two males and two females. Analyses of four aggressive behaviors (chase, bite, repel, spar) were conducted twice daily over a 5-day period, and fertilized eggs were collected for parentage analyses using DNA microsatellite markers. Dominant-subordinate relationships occurred both between males and between females, and in both sexes, dominance was associated with a greater body size and higher levels of aggression. During the spawning period, dominant females were, however, less aggressive toward their subordinates than dominant males to their subordinates. Aggressive behaviors employed for maintaining dominance did not differ between the sexes, but in females, in contrast with males, the level of aggression directed toward the subordinate fish increased over the study period. Overall, dominance resulted in a greater total reproductive success in males but not in females; however, dominant females sired more offspring with the dominant male. The findings illustrate that energy invested in dominance behavior appears beneficial for both sexes in zebrafish.
Phenotypic differences can exist between species, between local populations of the same species and between individuals within single local populations. At all scales, phenotypic differences can be either adaptive or non-adaptive. Using natural selection to explain differences between closely related species was controversial during the 1940s but had become common by the 1960s. Similarly, the adaptive nature of differences between local populations was initially controversial but had become widely accepted by the 1980s. The interpretation of differences at the finest scale, between individuals within single populations, is still unresolved. This paper reviews studies of adaptive individual differences in resource use and response to risk. A general conceptual framework for thinking about adaptive individual differences within populations can unite subjects as seemingly different as speciation and personality psychology.
The increasing use of zebrafish (Danio rerio) in developmental research highlights the need for a detailed understanding of their behavior. We studied the locomotion of individual zebrafish larva (6 days post-fertilization) in 96-well microtiter plates. Movement was recorded using a video-tracking system. Time of day results indicated locomotion, tested in darkness (infrared), decreased gradually from early morning to a stable level between 13:00 and 15:30 h. All further studies were conducted in early-to-late afternoon and lasted approximately 1 h. Each study also began with a period of darkness to minimize any unintended stimulation caused by transferring the plates to the recording platform. Locomotion in darkness increased initially to a maximum at 4 min, then decreased steadily to a low level by 20 min. Locomotion during light was initially low and then gradually increased to a stable level after 20 min. When 10-min periods of light and dark were alternated, activity was low in light and high in dark; curiously, activity during alternating dark periods was markedly higher than originally obtained during either extended dark or light. Further experiments explored the variables influencing this alternating pattern of activity. Varying the duration of the initial dark period (10-20 min) did not affect subsequent activity in either light or dark. The activity increase on return to dark was, however, greater following 15 min than 5 min of light. Acute ethanol increased activity at 1 and 2% and severely decreased activity at 4%. One-percent ethanol retarded the transition in activity from dark to light, and the habituation of activity in dark, while 2% ethanol increased activity regardless of lighting condition. Collectively, these results show that locomotion in larval zebrafish can be reliably measured in a 96-well microtiter plate format, and is sensitive to time of day, lighting conditions, and ethanol.
Individual minnows Phoxinus phoxinus and three?spined sticklebacks Gasterosteus aculeatus were provided with a mutually exclusive choice between joining a shoal of conspecifics and foraging alone in a maze. The shoaling decisions and foraging behaviour of individual fish were studied when the fish were satiated and after 24? and 48?h periods of food deprivation. Hunger level was found to have a significant effect on shoaling behaviour. When satiated, fish of both species spent a greater proportion of time within one body length of the shoal and spent less time out of visual contact with the shoal than after periods of food deprivation. The effect of the cestode parasite Schistocephalus solidus on the shoaling behaviour of stickleback hosts was complex. When satiated, infected fish spent less time than uninfected fish within one body length of the shoal, preferring to remain outside the shoal, yet within visual contact, although when food deprived there was no difference in the proportion of time spent by infected and uninfected fish close to the shoal. The possible ecological significance of this change in behaviour is discussed with reference to the manipulation hypothesis of host?parasite interactions.
Parenting in mantled howler monkeys (Alouatta palliata) requires a new set of energetic and behavioural demands. Because of constraints presented by the infant, as well as the increased energy requirements associated with mothering, parenting females need to change their activity patterns to ensure the successful upbringing of their offspring. This study of wild mantled howler monkeys was conducted to examine differences in activity between parenting and non-parenting adult females. Twenty two hours of continuous sampling on focal individuals was collected over the course of ten days in August at a study site in Nicaragua. It was found that the two groups do differ in their activity patterns: parenting females spent a larger percent of their time resting, feeding and interacting, but a lower percent of their time travelling when compared to non-parenting females. Further, it was found that parenting females engaged in scanning behaviours more frequently, and engaged in bridging (a locomotor behaviour) less frequently. These results suggest that parenting female mantled howler monkeys adopt an energy-minimizing activity pattern wherein the mothers compensate for their increased energetic requirements by only slightly increasing their food intake and instead drastically increasing the amount of time spent resting.
A considerable literature has been devoted to documenting differences between the sexes. However, relatively little attention has hitherto been directed towards those differences that arise as an indirect consequence of mating system even though they can have profound implications for the daily lives of the animals involved. In this review we focus on differences in the non-reproductive behaviour of fish and relate these to sexual dimorphism in size and morphology, and to variance in fitness between the sexes. In line with our expectation, differences in distributional ecology, schooling, aggression, predator avoidance and foraging are exaggerated in sexually dimorphic species and polygamous mating systems. Nonetheless, the behaviour of males and females may also differ in sexually monomorphic and monogamous species. We conclude by highlighting promising directions for further research.
Boldness and aggressiveness are two behavioural traits that have received extensive attention in the field of animal behaviour. However, relatively little is known about how these traits are maintained in populations and the fitness of individuals that exhibit them. We tested the effect of boldness and aggressiveness on the reproductive success of zebrafish, Danio rerio. Using behavioural tests, we established groups of males that varied consistently in their boldness (bold, middling and shy) as well as groups of males that differed in their aggressiveness (aggressive, middling and nonaggressive) and paired them with randomly selected females. We found no difference in the total number of eggs laid by females mated to bold or aggressive males. However, the number of fertilized eggs differed, with the boldest and the most aggressive males fertilizing more eggs than the other groups. Furthermore, the proportion of fertilized eggs differed between groups. These results show that an individual's reproductive fitness can be associated with behavioural variations in boldness and aggressiveness.
The process of domestication in fish is fundamentally important to conservation efforts because of the extensive use of hatcheries to mitigate population declines. Research into the genetic changes associated with the domestication process in many endangered species is impeded by a lack of genomic tools, long generation times, and large space requirements. The study of the genetics of fish domestication could therefore benefit from the introduction of a model system. In this paper, we document behavioral and growth rate differences observed between a domesticated laboratory strain of zebra danio (Danio rerio) and a strain newly introduced into the laboratory from its native habitat in India. Domesticated zebra danio showed a higher degree of surface orientation, a reduced startle response, and higher growth rate compared with wild zebra danio. Wilddomesticated interstrain hybrids were intermediate in phenotype for all traits. When strains were reared together, most interstrain behavioral differences were maintained, indicating a genetic basis underlying the interstrain phenotypic variation. Phenotypic differences observed in this study are consistent with the effects of domestication in other fish species, indicating that the zebra danio can be used as a model system for studying the genetics of the domestication process in fish.
Within a population there are frequently several discrete morphs. While in some cases, particularly color polymorphisms, this variation can be explained by simple Mendelian modes of inheritance, in many Gases the evidence suggests a polygenic pattern of inheritance. The threshold model of quantitative genetics, in which discrete morphs are determined by some underlying continuously distributed trail and a threshold(s) of expression, is applied appropriately in these cares. The discrete morphs exhibited in cyclomorphosis, pedomorphosis, pedogenesis, ''protective'' dimorphisms, trophic dimorphisms, wing dimorphism, and mating strategies can all be analysed by using this model. Analyses of a wide range of different types of threshold traits show that there is typically a large additive genetic component, but that there is also strong environmental induction. A review of studies shows that no morph has a universally higher fitness, but that there is a tradeoff with the relative fitnesses of two morphs being contingent upon environmental conditions. For example, exuberant structures that serve to protect organisms from predators reduce other components of fitness, such as development time and fecundity. Environmental induction is an adaptive non of reaction, in that cues of current or future conditions are used to increase the Probability that the morph produced is that which has the highest fitness under the expected conditions. Most models for the evolution of threshold traits have focused on the phenotype and have not addressed the crucial question of what maintains genetic variation, and hence permits continued evolutionary change. Phenotypic models show that noninducible polymorphic variation cannot be maintained by spatial variation alone, but can be favored in an environment that is temporally variable. Multiple phenotypes may evolve in a spatially variable environment if there are cues that allow the organism to assess the type of patch in which it is developing. thus spatial variation is expected to lead to the evolution of inducible phenotypes. Considerable genetic variation can be maintained by mutation, even in the face of strong directional selection. Frequency-dependent selection, shown to play an important role in the maintenance of phenotypic variation, may also be significant in the maintenance of genetic variation.
Individual minnows Phoxinus phoxinus and three-spined sticklebacks Gasterosteus aculeatus were provided with a mutually exclusive choice between joining a shoal of conspecifics and foraging alone in a maze. The shoaling decisions and foraging behaviour of individual fish were studied when the fish were satiated and after 24- and 48-h periods of food deprivation. Hunger level was found to have a significant effect on shoaling behaviour. When satiated, fish of both species spent a greater proportion of time within one body length of the shoal and spent less time out of visual contact with the shoal than after periods of food deprivation. The effect of the cestode parasite Schistocephalus solidus on the shoaling behaviour of stickleback hosts was complex. When satiated, infected fish spent less time than uninfected fish within one body length of the shoal, preferring to remain outside the shoal, yet within visual contact, although when food deprived there was no difference in the proportion of time spent by infected and uninfected fish close to the shoal. The possible ecological significance of this change in behaviour is discussed with reference to the manipulation hypothesis of host-parasite interactions.
(1) Pied wagtails defended winter feeding territories along a river. They fed on insects that were washed up onto the river banks. These formed a renewing food supply: after a stretch had been depleted, time was needed for prey abundance to return to a profitable level. The wagtail's feeding rate therefore depended on the time that had elapsed since the stretch was last depleted (the return time). (2) Territory owners increased their return time, and hence feeding rate, by systematic search around the territory and by evicting intruding conspecifics and other species that depressed their food supply. (3) Sometimes intruders landed on a territory undetected. This often decreased the owner's feeding rate because it visited stretches soon after they had been depleted by the undetected intruder. Juvenile intruders were more likely to land on a territory undetected, probably because they had duller plumage than the adults. (4) A territory was more profitable to an owner than to an intruder because the owner achieved greater return times. Intruders did worse because they did not know where the recently depleted stretches of the territory were. Even if intruders landed undetected, they often fed over areas that had recently been depleted by the owner. (5) Owners defended a territory of a fixed length, but their defence behaviour varied. Often the owner defended the territory alone but sometimes it associated with a subordinate (a satellite). Owners showed rapid changes in behaviour towards satellites; sometimes they chased them off and sometimes they allowed them to reside on the territory unmolested. (6) Satellites imposed a cost on the owner because they depleted the food supply on the territory. However, they also brought a benefit in the form of help with territory defence against intruders. (7) We develop a model which quantifies these costs and benefits, and show that owners vary their tolerance of satellites so as to maximize their own daily feeding rate. On days of high food abundance, when intruder pressure is greatest, owners tolerate satellites. We show that owners increase their feeding rate by this association, because the benefits gained through help with defence outweigh the costs incurred through sharing the food supply with another bird. On days of low food abundance, when an owner would have a higher feeding rate by being alone, it evicts the satellite from the territory.
1. Studies focusing on the physiological variation between populations and its con-nection to fitness-related traits are rare, even though integrating these fields would increase knowledge on the evolution of traits. Standard metabolic rate (SMR) has been suggested to influence an individual's social status and the level of aggressiveness, as dominant individuals tend to have higher SMR than subordinate individuals. 2. The SMR of juvenile Brown Trout (Salmo trutta) from four populations was measured, and the population-level relationship between SMR and aggressiveness, which is a fitness-related behavioural trait, was investigated. 3. SMR differed between the populations, but no differences were found in the amount of aggression. Nevertheless, a significant positive correlation between aggressiveness and SMR between the populations was found. 4. Unlike many previous studies on geographical variation of metabolic rate, SMR correlated negatively with the latitude of origin of the populations. 5. The results suggest that SMR and aggressiveness are correlated not only at the indi-vidual level as shown by previous studies, but also at the population level. The costs and benefits of high metabolic rate depend largely on the environment, and local differences in environmental conditions, as for example in food availability, may select for local differences in SMR.
Dominance is an important determinant of reproductive success in many species, and size is usually an indicator of dominance status, with larger, dominant individuals physically and physiologically preventing smaller subordinates from mating. However, small size may be advantageous in some mating contexts because enhanced manoeuvrability enables males to get closer to females during mating. Here, we determined the paternity success and testes size of dominant and subordinate male zebrafish ( Danio rerio), in pairs that controlled for social status. There was no statistical difference in both body size and testes size between dominant and subordinate males. Dominant males sired significantly more offspring than subordinates, but when subordinates were small, they had a greater share of the paternity than larger subordinates. Small male advantage may be one mechanism by which variation in body size is maintained in this species.
Behavioural traits that are consistent over time
and in different contexts are often referred to as personality
traits. These traits influence fitness because they play a
major role in foraging, reproduction and survival, and so it
is assumed that they have little or no additive genetic
variance and, consequently, low heritability because, theoretically,
they are under strong selection. Boldness and
aggressiveness are two personality traits that have been
shown to affect fitness. By crossing single males to multiple
females, we estimated the heritability of boldness and
aggressiveness in the zebrafish, Danio rerio. The additive
genetic variance was statistically significant for both traits
and the heritability estimates (95 % confidence intervals)
for boldness and aggressiveness were 0.76 (0.49, 0.90) and
0.36 (0.10, 0.72) respectively. Furthermore, there were
significant maternal effects accounting for 18 and 9 % of
the proportion of phenotypic variance in boldness and
aggressiveness respectively. This study shows that there is
a significant level of genetic variation in this population
that would allow these traits to evolve in response to
selection.
The Midas cichlid, Cichlasoma citrinellum, is monogamous and biparental. Because of competition for limited spawning sites and intense predation on their young, vigorous defense of their territory is essential. Although both sexes engage in defense, they differ in aggressiveness.
The aggressive responses of both sexes were measured by counting the number of bites and bumps each fish directed toward its own mirror image. The size of the fish's genital papilla was also recorded to estimate its reproductive state.
Compared with females, males had higher median mirror scores with greater variance. The scores of individual males were also more consistent through time than were those of females. Females close to spawning had the highest mirror scores, whereas male scores were highest early in the reproductive cycle.
Selection has apparently favored aggressiveness in both sexes. We argue, however, that differences in aggression are the result of selection acting dissimilarly on the two sexes.
IntroductionLateralized functions in fishIndividual differences in lateralizationEcological consequences of lateralization of cognitive functionsSummary and future researchAcknowledgementsReferences
A considerable literature has been devoted to documenting differences between the sexes. However, relatively little attention has hitherto been directed towards those differences that arise as an indirect consequence of mating system even though they can have profound implications for the daily lives of the animals involved. In this review we focus on differences in the non-reproductive behaviour of fish and relate these to sexual dimorphism in size and morphology, and to variance in fitness between the sexes. In line with our expectation, differences in distributional ecology, schooling, aggression, predator avoidance and foraging are exaggerated in sexually dimorphic species and polygamous mating systems. Nonetheless, the behaviour of males and females may also differ in sexually monomorphic and monogamous species. We conclude by highlighting promising directions for further research.
Studies focusing on the physiological variation between populations and its connection to fitness‐related traits are rare, even though integrating these fields would increase knowledge on the evolution of traits. Standard metabolic rate (SMR) has been suggested to influence an individual’s social status and the level of aggressiveness, as dominant individuals tend to have higher SMR than subordinate individuals.
The SMR of juvenile Brown Trout ( Salmo trutta ) from four populations was measured, and the population‐level relationship between SMR and aggressiveness, which is a fitness‐related behavioural trait, was investigated.
SMR differed between the populations, but no differences were found in the amount of aggression. Nevertheless, a significant positive correlation between aggressiveness and SMR between the populations was found.
Unlike many previous studies on geographical variation of metabolic rate, SMR correlated negatively with the latitude of origin of the populations.
The results suggest that SMR and aggressiveness are correlated not only at the individual level as shown by previous studies, but also at the population level. The costs and benefits of high metabolic rate depend largely on the environment, and local differences in environmental conditions, as for example in food availability, may select for local differences in SMR.
1. Agonistic behaviour can be an important trait in determining individual success under interference competition, but it also generates energetic and physiological costs. The ensuing trade-off is expected to be dependent on the individual state. This study tests whether aggression patterns of juvenile Atlantic Salmon Salmo salar are linked to the recent growth history and the developmental pathway adopted by fish (early vs late migrants).
2. By manipulating growth rates over 1 month in the autumn, three groups of fish were produced differing in body size and thereby in the length increment necessary to achieve the threshold size for migration in the following spring. Fish that had experienced reduced rations or abnormally low temperatures during the manipulation period experienced ‘catch-up’ growth after the resumption of standard growth conditions.
3. Aggression was strongly connected to growth bimodality and the underlying developmental polyphenism. Fast-growing (upper modal group, UMG) fish (which would migrate in the spring) were more aggressive than slow-growing (lower modal group, LMG) fish (which would delay migration for another year), but they were also more vulnerable to being attacked by conspecifics.
4. Aggressive acts initiated by UMG fish were strongly biased towards fish of the same category (57–77% of aggressive acts being against other UMG fish). Under illumination conditions simulating overcast nights, UMG individuals sharply reduced their aggressiveness and were not selective in their attacks. The aggression by LMG fish was more evenly distributed between modal groups (44–74% of attacks were against UMG) regardless of light levels.
5. Recent growth history had no consistent effect on aggression rates, although under overcast night conditions the rate of attacks received by non-manipulated UMG fish was twice as high as that for fish undergoing compensatory growth.
6. These results demonstrate a link between developmental pathways and aggression patterns. They also show that individuals maintaining a fast growth strategy over the winter experience a more aggressive social environment than individuals adjusting feeding rates to ensure safe maintenance levels. The reduced involvement of LMG fish in agonistic encounters conforms to a strategy of avoidance of those energetic and physiological costs that ultimately could compromise overwintering survival.
The boldness of individual Brachyrhaphis episcopi, collected from regions of high and low predation, was investigated using two independent assays: (1) the time to emerge from cover and (2) the propensity to leave shoal mates and investigate a novel object. A strong correlation between the two assays was revealed such that fish that emerged from shelter sooner were also more likely to approach a novel object. This is indicative of a boldness personality axis acting across both behavioural contexts. Fish from high-predation areas were bolder than those from low-predation areas and males were bolder than females. A significant correlation between body mass, standard length (LS) and boldness score was also found. In general, bold fish had a greater body mass at a given LS than shy fish. These results suggest that personality traits are strongly influenced by population-specific ecological variables and may have fitness consequences in wild populations.
Experiments were conducted to monitor changes in body mass and metabolic energy expenditure before, during, and after periods of starvation in juveniles of three species of cyprinids: Leuciscus cephalus, Chalcalburnus chalcoides mento, and Scardinius erythrophthalmus. During the starvation period all fish lost weight at about the same rate and the total amount of oxygen consumed during an experimental period of 20 h was about 40% lower in the starved than in the fed groups. Upon refeeding, both mass specific maintenance; and routine rates of metabolism as well as relative growth rates increased rapidly, the peaks of these increases being directly proportional to the length of the starvation period. Maximum compensatory growth was observed after four weeks of starvation in C. chalcoides and S. erythrophthalmus, with relative growth rates reaching 30% d-1 during the first measuring interval after refeeding. The pattern of time-dependent compensatory growth displayed by these fish is similar to the responses of a colonial hydroid in which the rate of catch-up growth increased with the amount of stress to which the animals had been exposed. The exact cost of compensatory growth cannot be calculated because oxygen consumption and growth were not measured simultaneously. However, on the basis of data and calculations reported by Wieser & Medgyesy (1990) it appears that compensatory growth, if fuelled by the metabolic power indicated by our measurements of oxygen consumption, would have to be about twice as efficient as normal growth in the related species Rutilus rutilus.
Skew in the operational sex ratio of a population can have important consequences for mating competition and typically results in differential mating success. Population density can also influence mating behaviour and may interact with the operational sex ratio. We investigated the effects of both density and operational sex ratio on male territoriality and female oviposition in the zebrafish. We manipulated the sex bias in favour of either males or females at two density levels and measured the impact on females of aggression and courtship behaviour by territorial males in terms of egg production. Total egg production increased as a function of the number of females in each of the four treatments. However, mean per capita egg production was lower at high densities. We propose that this effect was due to increased aggression at high densities by territorial males towards rivals, which interrupted female spawning attempts. At high densities, territorial males maintained high rates of aggression regardless of sex bias, but courtship rates were significantly lower in male-biased treatments. We further propose that this response, whereby males constrain courtship in the presence of potential rivals, may be adaptive in the context of sperm competition avoidance.
Competition among females represents an important but rather neglected variable in studies of sexual selection. Probably to avoid injury to self and offspring, competition among females is often displayed without much physical interaction and therefore remains harder to observe. Here, we show for the first time in a teleost fish, the zebrafish Danio rerio, that females can use waterborne pheromones to suppress reproduction by other females. Female zebrafish that had been exposed to another female's pheromones for 4 days prior to mating spawned significantly fewer viable eggs than females held in isolation or exposed to male pheromones. Male pheromones not only stimulated female reproduction but also increased the quality and viability of eggs. In grouped females, reproductive success correlated with dominance rank. These results indicate that fish pheromones function to control mates and competitors in addition to serving as reproductive timing signals. Differences in female reproductive success observed in many fish species might be explained by this mechanism.
The grouping behaviour of fish is a widespread phenomenon of high biological significance but little is known as to how consistent individual behavioural differences may affect group joining preferences. When given the option to join either a shy or a bold shoal of three-spined sticklebacks, Gasterosteus aculeatus, both shy and bold individuals showed a strong preference for associating with bold fish. Personality type interacted with individual hunger levels to affect the extent of association, suggesting important strategy variation by focal fish in a competitive foraging environment. Furthermore, shoals modified their behaviour in relation to the focal individual. Individual behavioural differences were shown to have a complex role in influencing association preferences as well as driving previously unrecognized behavioural modifications in foraging groups.
Explaining consistent variation in the behaviour of individuals in terms of personality differences is one of the cornerstones of understanding human behaviour but is seldom discussed in behavioural ecology for fear of invoking anthropomorphism. Recently, however, interest has begun to focus on identifying personality traits in animals and examining their possible evolutionary consequences. One major axis used to define personality traits is the shyness–boldness continuum. We examined boldness in an in situ experiment using fish from eight populations of the poeciliid Brachyraphis episcopi (also referred to as Brachyrhaphis episcopi). Fish from high- and low-predation regions within four streams that run independently into the Panama Canal were tested. Boldness scores were strongly influenced by standard length and the relative level of predation pressure in the rivers. In all four rivers, fish from high-predation areas were bolder than those from low-predation areas. Fish became increasingly shy as they grew.
Individual variation in behaviour within populations may be explained in part by demographics and long-term, stable individual psychological differences. We examined the relation between boldness (taken as the time to emerge from a shelter and explore a novel environment) and body size in eight populations of the poeciliid Brachyraphis episcopi originating from sites upstream and downstream of waterfalls in four rivers that run into the Panama Canal. The relation between body size and time to emerge from a shelter was positive, with larger fish taking longer to emerge. This relation differed between downstream and upstream sites, being significant in the upstream populations only. These results are best explained by a metabolic hypothesis whereby juvenile fish are compelled to emerge earlier in order to resume feeding. In the downstream sites this effect was slightly offset by the relatively greater predation threat for smaller fish, such that they delayed their emergence from cover. We discuss the underlying importance of variation in boldness and its effects on other behavioural and life history traits.
In this paper we show how animal personality could explain some of the large inter-individual variation in resting metabolic rate (MR) and explore methodological and functional linkages between personality and energetics. Personality will introduce variability in resting MR measures because individuals consistently differ in their stress response, exploration or activity levels, all of which influence MR measurements made with respirometry and the doubly-labelled water technique. Physiologists try to exclude these behavioural influences from resting MR measurements, but animal personality research indicates that these attempts are unlikely to be successful. For example, because reactive animals “freeze” when submitted to a stress, their MR could be classified as “resting” because of immobility when in fact they are highly stressed with an elevated MR. More importantly, recent research demonstrating that behavioural responses to novel and highly artificial stimuli are correlated with both behaviour and fitness under more natural circumstances calls into question the wisdom of excluding these behavioural influences on MR measurements. The reason that intra-specific variation in resting MR are so weakly correlated with daily energy expenditure (DEE) and fitness, may be that the latter two measures fully incorporate personality while the former partially excludes its influence. Because activity, exploration, boldness and aggressiveness are energetically costly, personality and metabolism should be correlated and physiological constraints may underlie behavioural syndromes. We show how physiological ecologists can better examine behavioural linkages between personality and metabolism, as required to better understand the physiological correlates of personality and the evolutionary consequences of metabolic variability.
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Factors affecting emergence by prey that enter refuges when approached by predators have been studied intensively, but only two theoretical models predict how long prey should remain in a refuge before emerging. We argue that prey can make better decisions than allowed by one model; the other model describes cases in which predators wait for prey to emerge. We present optimality models that permit prey to select a time to emerge that maximizes fitness. When in a refuge, a prey cannot obtain benefits outside; emerging too soon can be catastrophic, but delaying emergence entails loss of fitness. If predators resume foraging quickly rather than engaging in strategic waiting games, current theory suggests that prey emerge when the costs of remaining in a refuge and of emerging are equal. However, prey often can do better by emerging at the time maximizing fitness rather than when benefits equal costs (i.e. when prey break even). Optimal emergence time depends on initial fitness, benefits lost by remaining in refuge, and the decay rate of predation risk. Benefits lost if a prey is killed are modelled separately from benefits that contribute to lifetime fitness, even if the prey is killed (individual reproduction, altruism). Fitness of prey emerging at the optimal emergence time may be greater than, equal to or less than initial fitness. Break-even and optimality models base predictions on the opposing effects of risk and loss of benefits. Thus, many empirically verified predictions are identical at the ordinal level although differing quantitatively. Optimality models provide novel testable predictions for the effects of initial fitness, benefits, and, for ectotherms, the rate of cooling in refuge. They predict earlier emergence for equal retainable benefits than for those lost upon death. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 375–382.
Mating success tends to be skewed toward dominant males, though female mate preferences may not always correlate with male
dominance. In this study, we investigated the mating preferences of female zebrafish, Danio rerio, in the absence of male–male competition. We paired females sequentially with males of known dominance rank, using a nested,
repeated measures design, with egg production as a measure of female mate preference. We predicted that females would spawn
more frequently and produce larger clutches when paired with males of higher dominance rank. We found significant differences
among females in the size of clutches produced and among males in the size of clutches received, but these differences were
independent of male dominance rank. Male body size was not related to either dominance rank or clutch size received. These
results indicate that females vary clutch size in relation to the males with which they are paired but that they do not favor
dominant males. Thus, male competition may normally override female mate preference in zebrafish.
A main aspect of these two alternative strategies is that individuals with an active strategy easily develop routines (intrinsically determined behaviour), and consequently do not react (properly) to ‘minor’ changes in their environment, whereas in passively reacting animals it is just the other way around (extrinsically determined behaviour). It has become clear that active and passive behavioural strategies represent two different, but equivalent, coping styles. The coping style of the aggressive males is aimed at the removal of themselves from the source of stress or at removal of the stress source itself (i. e. active manipulation). Non-aggressive individuals seem to aim at the reduction of the emotional impact of the stress (i.e. passive confrontation). The success of both coping styles depends upon the variability or stability of the environment. The fact that aggressive males develop routines may contribute to a fast excution of their anticipatory responses, which is necessary for an effective manipulation of events. However, this is only of advantage in predictable (stable) situations, but is maladaptive (e.g. expressed by the development of stress pathologies) when the animal is confronted with the unexpected (variable situations). The flexible behaviour of non-aggressive individuals, depending strongly upon external stimuli, will be of advantage under changing conditions. Studies on wild house mice living under natural conditions show how active and passive coping functions in nature, and how the two types have been brought about by natural selection.
Aggression consumes important amounts of energy (e.g., in fish the effort of "routine" social life may be as costly as life-long forced swimming at moderate speeds). In fish the amount of energy spent and the metabolic compartment mobilized seem to depend on the length of cohabitation, the number of contestants and the result of the fight. In mammals, metabolic preparations for fights were shown. The fights cause elevations of both body temperature and metabolic rate, as well as important changes in carbohydrate and lipid metabolism. There are evidences which show that the energetic aspects of aggressive behavior have a significant impact on the behavioral tactics and survival chances in free living animals. The relevance of these studies to game theoretical analyses and to practical aspects of the aggression-energy metabolism interrelationship are also outlined. Although many details of the phenomenon are known, important issues have to be clarified, among them the possible neuroendocrinologic co-regulation of this behavior and of its energetic background.