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Prozac impacts lateralization of aggression in male Siamese fighting fish

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Previous studies have shown that Siamese fighting fish, Betta splendens, preferentially use right-eye during the aggressive displays. However, administration of antidepressant drugs may disrupt eye-use preference in association with a reduction in aggression; a phenomena that has not been explored in fish. The objective of the current study was to examine the effects of exposure to the antidepressant drug, fluoxetine, on lateralization in eye-use during aggressive displays in male Siamese fighting fish. Baseline aggression and lateralization in eye use of thirty fish were assessed toward live conspecifics, following which experimental subjects (n=15) were then exposed to fluoxetine (540 ng/L) in a static renewal water system. Behavior was quantified again after 9 days of exposure. All of the subjects preferentially used the right-eye during aggressive responses before the exposure experiments. Fluoxetine exposed subjects showed a reduction in the time spent gill flaring as has previously been reported, indicative of a reduction in the level of aggression. Fluoxetine also had a significant effect on the lateralization in preferred eye-use while looking at their opponent. Fish exposed to fluoxetine switched from a preferential use of the right-eye during aggressive encounters prior to exposure to using their left-eye after exposure to fluoxetine. The results are discussed with regard to asymmetrical distribution of serotonin between the two brain hemispheres.
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... Once the betta's aggressive behavioral phenotype and conditioning was established research with this model shifted focus to tests of pharmaceuticals to establish similarities between teleost and mammalian models and identify chemical impacts on social dominance and contest behavior in the context of mating (Dzieweczynski et al., 2005;Eisenreich and Szalda-Petree, 2015;Eisenreich et al., 2017). Fluoxetine, an antidepressant and selective serotonin reuptake inhibitor (SSRI), has been studied extensively with bettas in an attempt to identify the impact changes to serotonin have on social dominance behavior (Lynn et al., 2007;Dzieweczynski and Hebert, 2012;Kohlert et al., 2012;Greaney et al., 2015;Eisenreich and Szalda-Petree, 2015;Eisenreich et al., 2017;HedayatiRad et al., 2017). Changes to the serotonin system have been shown to impact aggression in vertebrates, with increases of serotonin leading to decreases in aggressive behavior (Lynn et al., 2007;Ansai et al., 2016). ...
... Changes to the serotonin system have been shown to impact aggression in vertebrates, with increases of serotonin leading to decreases in aggressive behavior (Lynn et al., 2007;Ansai et al., 2016). Many studies addressing the impacts of fluoxetine in regard to aggressive behavior have all found decreased aggressive responding compared to controls despite the wide range of manipulations and testing apparatuses (Lynn et al., 2007;Dzieweczynski and Hebert, 2012;Kohlert et al., 2012;Greaney et al., 2015;Eisenreich and Szalda-Petree, 2015;Eisenreich et al., 2017;HedayatiRad et al., 2017). There are two behavioral mechanisms of action contributing to behavioral changes in bettas exposed to fluoxetine: movement and motivation (Eisenreich and Szalda-Petree, 2015;Eisenreich et al., 2017). ...
... The main findings of this study were the effects of fluoxetine on male latency, courting, and fighting behavior. These effects are consistent with previous findings of decreased movement and arousal to aggress against a mirror or conspecific in bettas when exposed to the SSRI fluoxetine (Lynn et al., 2007;Dzieweczynski and Hebert, 2012;Kohlert et al., 2012;Greaney et al., 2015;Eisenreich and Szalda-Petree, 2015;Eisenreich et al., 2017;HedayatiRad et al., 2017). Furthermore, the data showing fluoxetine's negative effects on agonistic behaviors seen during male encounters supports the hypothesis of decreased arousal in male fish exposed to SSRI's. ...
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While an extensive literature has demonstrated that the selective serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine, disrupts aggressive behavior in male Betta splendens the behavioral mechanisms underlying this disruption remain unknown. To elucidate the behavioral mechanism underlying fluoxetine, male fish were acutely exposed to a 10 μmol (0.0034578 μg/L) concentration of fluoxetine for 25 days using an ABA design. Male Betta splendens are naturally aggressive fish with well-studied and patterned behavioral responses. Importantly, aggressive behavior in this species can be conditionally primed allowing for examination of motivational components of behavior in addition to motor performance. The present study focused on using female fish as an ecologically relevant prime for eliciting aggressive behavior as a means of examining the motivational and motoric effects of fluoxetine. We found that male courtship with a female was strongly correlated with aggressive responding against a mirror. However, despite the strong correlation male fish were not found to have different levels of aggression or changes in aggressive responding when compared to males not primed with a female. Also, latency was not different between the no female prime and female prime males for either the excitatory mirror condition or inhibitory white wall condition, of which the fish had no preference. However, fluoxetine was found to have profound effects on all males in the study regardless of prime type, with increases in latency for the mirror and white wall and decreases in aggressive responding to the mirror. These results support the hypothesis that fluoxetine impairs aggressive motivation and movement in Betta splendens.
... Yes Sovrano et al., 1999Males No Sovrano et al., 1999 Angelfish (Pterophyllum scalare) Yes Sovrano et al., 1999 Eurasian minnow (Phoxinus phoxinus) Yes Sovrano et al., 1999 (Continued) Frontiers in Neuroanatomy | www.frontiersin.org Sovrano et al., 1999 Sarasins minnow (Xenopoecilus sarasinorum) Yes Sovrano et al., 2001;Sovrano, 2004 Elephantnose fish (Gnathonemus petersii) Yes Sovrano et al., 2001 Soldierfish (Myripristis pralinia) Yes Roux et al., 2016 Mating behavior Mosquitofish (Gambusia hoolbrooki) Yes Bisazza et al., 1998 Goldbelly topminnow (Girardinus falcatus) Yes Bisazza et al., 1998 Guppy (Poecilia reticulata) Yes Kaarthigeyan and Dharmaretnam, 2005 Agonistic behavior Siamese fighting fish (Betta splendens) Yes Cantalupo et al., 1996;Bisazza and De Santi, 2003;Clotfelter and Kuperberg, 2007;Takeuchi et al., 2010;Forsatkar et al., 2015;HedayatiRad et al., 2017 Mosquitofish (Gambusia hoolbrooki) Yes Bisazza and De Santi, 2003 Redtail splitfin (Xenotoca eiseni) Yes Bisazza and De Santi, 2003 asymmetries rather than behavioral lateralization induced by eye-use preference (Stennett and Strauss, 2010). Rotational bias represents another example of motor asymmetry. ...
... The same right bias has been recently reported by Forsatkar et al. (2015) in nest-holding males fighting fish although the stages of reproduction and the paternal care affected the eye-preference with a shift from the righteye to the left-eye after spawning. Similarly, exposure to an antidepressant drug (fluoxetine) reduced aggressive behavior and caused a change from a right to a left-eye use in this species even if the underlying mechanisms are still unknown (HedayatiRad et al., 2017). ...
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It is widely acknowledged that the left and right hemispheres of human brains display both anatomical and functional asymmetries. For more than a century, brain and behavioral lateralization have been considered a uniquely human feature linked to language and handedness. However, over the past decades this idea has been challenged by an increasing number of studies describing structural asymmetries and lateralized behaviors in non-human species extending from primates to fish. Evidence suggesting that a similar pattern of brain lateralization occurs in all vertebrates, humans included, has allowed the emergence of different model systems to investigate the development of brain asymmetries and their impact on behavior. Among animal models, fish have contributed much to the research on lateralization as several fish species exhibit lateralized behaviors. For instance, behavioral studies have shown that the advantages of having an asymmetric brain, such as the ability of simultaneously processing different information and perform parallel tasks compensate the potential costs associated with poor integration of information between the two hemispheres thus helping to better understand the possible evolutionary significance of lateralization. However, these studies inferred how the two sides of the brains are differentially specialized by measuring the differences in the behavioral responses but did not allow to directly investigate the relation between anatomical and functional asymmetries. With respect to this issue, in recent years zebrafish has become a powerful model to address lateralization at different level of complexity, from genes to neural circuitry and behavior. The possibility of combining genetic manipulation of brain asymmetries with cutting-edge in vivo imaging technique and behavioral tests makes the zebrafish a valuable model to investigate the phylogeny and ontogeny of brain lateralization and its relevance for normal brain function and behavior.
... Chronic administration of piracetam also reduces fear behavior in zebrafish where fish spend more time in a white area in a scototaxic (light versus dark chamber) test [86]. Similarly, there are numerous ecotoxicological studies indicating that fish respond to pharmaceuticals such as fluoxetine (Prozac) in a manner similar to humans (e.g., [87]). These examples demonstrate the capacity for fear in fishes and clearly show that the underlying physiological mechanisms and neural substrates are similar. ...
... We still do not fully understand what fishes make of their own mirror image. Many fish species seem to treat mirror images as unfamiliar conspecifics although the responses are not the same as when they first meet a real unfamiliar fish [110][111][112][113]. Male Siamese fighters, for example, initially respond as if the image is a rival and they behave aggressively toward it [87,114]. Many species, however, treat the image as a social companion or gradually ignore it [113]. ...
Chapter
Fish models are increasingly used in a wide variety of experimental contexts and their adoption is growing globally. This chapter reviews the evidence for sentience and cognitive abilities in fishes to highlight the growing empirical evidence of the mental capacities of fish. The definition of sentience is presented along with the scientific data pertinent to understanding what fishes are capable of, as well as higher order cognitive abilities such as numerical skills and the capacity for learning and memory. Being able to experience positive and negative welfare states such as pain, fear, and stress is highly debated for fishes; thus this chapter reviews the evidence for and arguments against conscious perception of pain and fear. If suffering and sentience are accepted in fishes, this has ethical implications for the way in which we use fish in scientific studies.
... Model species such as zebrafish (Danio rerio) and medaka (Oryzias latipes) are extensively used in large-scale screening of drugs (e.g. MacRae and Peterson 2015), while Siamese fighting fish (Betta splendens) has been exploited in behavioral toxicology studies (Forsatkar et al. 2014;Dzieweczynski et al. 2014;HedayatiRad et al. 2017). Owing to the conservative nature of vertebrate physiology, results from fish models may be applicable to other vertebrates including humans (Kari et al. 2007). ...
... Specimens were stocked individually in 500 mL transparent plastic containers filled to 300 mL old tap-water. Water temperature was controlled by warming the environment and set at 26 ± 0.5°C as recommended for betta fish (HedayatiRad et al. 2017). Levels of pH (7.2-7.8) and ammonia (<0.5 mg/L) were kept within the optimum levels by partial water changes every three days. ...
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Siamese fighting fish (Betta splendens) has been extensively exploited in the behavioral and physiological toxicology studies of drugs. Tacrolimus is an immunosuppressant drug largely used in liver and renal transplantations. Here we found that a 7-day exposure of male B. splendens to concentrations of 0.05 and 0.1 µg/mL Prograf® (tacrolimus) caused alterations in aggression and immunity indexes. Tacrolimus exposed fish presented lower opercular display in a mirror test which is indicative of reduced aggression. In addition, serum levels of lysozyme, IgM, alternative complement, and bactericidal activity of subjects exposed to 0.1 µg/mL tacrolimus were lower than those from the control treatment. These results showed the behavioral impairment and immunotoxic impacts of tacrolimus in a model of aquatic toxicology. The results suggest fishes provide a possible model for better understanding of the drug action in vertebrates, and possible consequences for the environment via its effects on non-target organisms in an ecotoxicology context.
... Several studies have also examined the effect of environmental stressors on foraging efficiency (e.g., Figueiredo et al. 2016), collective behavior (e.g., Herbert-Read et al. 2017;Chamberlain and Ioannou 2019), or avoidance of model predators (e.g., Webber and Haines 2003), among other behaviors. Siamese Fighting Fish, for example, are often employed in ecotoxicology studies because their aggressive behavior is so well documented (e.g., Hedayatirad et al. 2017;Khoei et al. 2019). One consideration with many of these environmental and toxicological studies is the method and duration of exposure; acute and chronic exposure will prompt drastically different responses, and one should choose a method that is biologically relevant (see Murphy et al. 2021, Chapter 15, this volume). ...
Chapter
Methods for Fish Biology, 2nd edition Chapter 16: Behavior Julianna P. Kadar, Catarina Vila Pouca, Robert Perryman, Joni Pini-Fitzsimmons, Sherrie Chambers, Connor Gervais, and Culum Brown doi: https://doi.org/10.47886/9781934874615.ch16 Kadar, J. P., C. V. Pouca, R. Perryman, J. Pini-Fitzsimmons, S. Chambers, C. Gervais, and C. Brown. 2022. Pages 593–642 in S. Midway, C. Hasler, and P. Chakrabarty, editors. Methods for fish biology, 2nd edition. American Fisheries Society, Bethesda, Maryland. Humans interact with fish in a wide variety of contexts. Fish are rapidly becoming the go-to model for medical research because of the conservative nature of vertebrate physiology. We catch and grow fish in captivity for human consumption and frequently rear fish for release into the wild either to supplement wild populations to enhance fisheries or as a conservation measure. In all cases, understanding fish behavior is vital whether you are interested in stock management, conservation biology, or animal welfare (Brown 2015). Gone are the days when fish were viewed as mindless automata. We now know that fish behavior is highly flexible, providing the plasticity to allow individuals to adjust to prevailing conditions or contexts (Bshary and Brown 2014). Their level of cognitive and behavioral sophistication is on par with the rest of the vertebrates (Bshary and Schäffer 2002; Vila Pouca and Brown 2018a; 2018b). Unsurprisingly, a change in behavior is often the first sign that something has shifted in the environment; thus, behavioral studies are at the forefront of environmental and ecotoxicological research (Brown 2012; Oulton et al. 2014). The massive diversity of fishes (currently more than 32,000 described species), and the range of niches they occupy, means that generalization is nearly impossible. Thankfully, the approaches for studying fish behavior are also many and varied and rapidly developing with changes in technology. Here we provide a brief overview of some of the emerging methods for studying fish behavior. We will not be reviewing fish behavior in general since this is the topic of multiple books (e.g., Magnhagen et al. 2008; Brown et al. 2011), nor will we be providing a general overview of how to study animal behavior. Such details can readily be found in any of the many excellent texts on animal behavior or behavioral ecology (Davies 1991; Dugatkin and Earley 2004; Alcock 2005; Goodenough et al. 2009). Many people study fish behavior under captive conditions where it is possible to control the environment and observe behaviors that can be attributed to specific cognitive processes. In most instances, it is simply a matter of refining the standard methods to suit the aquatic environment and the species of interest. The main difficulties of studying fish behavior arise when trying to observe them in their natural environment. The underwater world is not a place with which most people are comfortable or familiar. Humans can stay only so long in the watery world of fishes, so many of the methods we describe here attempt to overcome these problems by studying fish behavior remotely.
... The Siamese fighting fish is a particularly attractive model for behavioural quantification thanks to its explicit antagonistic display (Thompson 1963;Simpson 1968). Furthermore, because atypical aggression is associated with a range of pathological conditions and drugs are easily delivered to fish via their natural medium, fighting fish are of interest to pharmacological studies (Lynn et al. 2007;Eisenreich et al. 2017;Dzieweczynski et al. 2016;HedayatiRad et al. 2017). To support targeted drug delivery and manipulation, however, it is imperative that aggressive behaviour is characterized and understood to a satisfactory degree of specificity. ...
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We currently have limited knowledge about complex visual representations in teleosts. For the specific case of Siamese fighting fish (Betta splendens), we do not know whether they can represent much more than mere colour or size. In this study, we assess their visual capabilities using increasingly complex stimulus manipulations akin to those adopted in human psychophysical studies of higher-level perceptual processes, such as face recognition. Our findings demonstrate a surprisingly sophisticated degree of perceptual representation. Consistent with previous work in established teleost models like zebrafish (Danio rerio), we find that fighting fish can integrate different features (e.g. shape and motion) for visually guided behaviour; this integration process, however, operates in a more holistic fashion in the fighting fish. More specifically, their analysis of complex spatiotemporal patterns is primarily global rather than local, meaning that individual stimulus elements must cohere into an organized percept for effective behavioural drive. The configural nature of this perceptual process is reminiscent of how mammals represent socially relevant signals, notwithstanding the lack of cortical structures that are widely recognized to play a critical role in higher cognitive processes. Our results indicate that mammalian-centric accounts of social cognition present serious conceptual limitations, and in so doing they highlight the importance of understanding complex perceptual function from a general ethological perspective.
... To acquire territory and mating opportunities, male betta fish compete fiercely with each other by employing well documented behavioral displays that include gill flaring, darting, finning and lateral displays during swimming (Brown and Clotfelter, 2012;Gozlan et al., 2003). Once males have successfully defended a territory, they must build a bubble nest and then defend it from egg and larva predation for a few days following egg laying by the female (HedayatiRad et al., 2017). Nest building behavior in betta fish is thus a key component needed for successful reproduction (Jaroensutasinee and Jaroensutasinee, 2003). ...
Article
Uptake by fishes of crude oil and its polycyclic aromatic hydrocarbons (PAHs) components occurs via gills, dietary intake, or diffusion through the skin. Dietary exposure to crude oil and its components is environmentally relevant, and induces physiological and morphological disruptions in fish. However, the impacts of crude oil on fish social and reproductive behaviors and thus the possible influences on reproductive success are poorly understood. As a part of their intraspecific interactions, male Siamese fighting fish (Betta splendens) exhibit highly stereotypic behavioral and territorial displays. This makes this species a tractable model for testing crude oil effects on behavior. After 2 weeks of acclimation at 29 °C, male adult betta fish were divided into three groups and fed for 4 weeks with food spiked with water (control), low oil concentrations or high oil concentrations (∑Total PAH concentrations 340, 3960 or 8820 ng/g dw, respectively) to determine subsequent alterations in behavioral displays. Compared with control fish, the aggressive display of “opercular flaring” was significantly increased (P < 0.03, n = 14-16) in oil-exposed fish. Bubble nest building, as well as testis and brain mass, were significantly reduced in treated fish (P < 0.05). Hematocrit of treated groups was increased significantly (P < 0.02) from 21% in control fish to ~27% in both oil exposure groups. Dietary exposure over a 4-week period to low, relevant levels of crude oil thus leads to an increase in aggressive behavioral displays, a decrease in reproductive activity and additional morphological changes.
... Fish exposed to cortisol exhibited a higher degree of turning bias compared to fish of the control condition. On the opposite side, the exposure of Siamese fighting fish (Betta splendens) to the antidepressant drug fluoxetine (Prozac) caused both a decrease in the aggressive displays and a switch in the preferential eye use during aggressive encounters, from the right to the left eye (HedayatiRad et al., 2017). Overall, these results provide evidence that lateralization is a highly variable trait, whose expression can be modulated within days or even hours. ...
Chapter
The study of brain and behavioral lateralization in so-called “lower vertebrates” (fish, amphibians, and reptiles) has received increasing attention in the last years, in an attempt to understand its phylogenetic origins and evolutionary significance. Observations on the earliest tetrapods, the amphibians, have helped us to understand the evolution of limb preference and suggest that laterality could have appeared even prior to the evolution of tetrapods. Insights into lateralized behaviors in fish—such as the turning behavior—have had an important role in uncovering proximate and ultimate causes of motor lateralization in the vertebrate subphylum. Additionally, investigations on the alignment of behavioral preferences in fish populations have helped do develop formal models to explain the unequal distribution of left- and right-lateralized individuals as the result of evolutionarily stable strategies among lateralized asymmetric individuals that interact cooperatively or competitively.
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The selective serotonin reuptake inhibitor fluoxetine has frequently been detected in surface waters around the world. Fluoxetine modulates levels of serotonin, a neurotransmitter that regulates several important physiological and behavioural processes including fear and anxiety, aggression, locomotion and feeding. In this study, groups of sub-adult Arabian killifish (Aphanius dispar) were exposed to either 0, 0.03, 0.3 or 3 μg/L fluoxetine hydrochloride for 7 days and their swimming behaviour and social interactions videotaped in a circular arena. The fish were subsequently exposed to a predator alarm chemical (from dragonfly larvae fed with A. dispar) and their short-term responses recorded. The video was analysed using the open-sourced software program Ctrax which objectively quantified swimming and social behaviours. Aggression (chasing behaviour was significantly reduced at 3.0 μg/L fluoxetine. After the addition of the predator alarm chemicals fish responded quickly, increasing the percentage of time spent drifting or motionless and reducing average swimming velocity. Controls and fish exposed to 0.03 or 3 μg/L fluoxetine reduced swimming speed by 20-30 % but returned to pre-exposure velocities within 6 min. Fish exposed to 0.3 μg/L fluoxetine reduced swimming speed by 38 % after addition of the predator alarm and did not return to pre-exposure speeds during the recording period (19 min). Schooling behaviour was also affected by fluoxetine and predator alarm with fish exposed to 0.3 μg/L fluoxetine significantly reducing nearest neighbour distance and swimming speed relative to nearest neighbour the following addition of the predator alarm.
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Mercury chloride (HgCl2) is a toxic mercury salt and a major pollutant, that can be found in soil, water and air, with influences on behavior, physiology and adaptation to the environment. In this study two experiments were designed to examine interactions and effects of HgCl2 on some behavioral patterns of Siamese fighting fish (Betta splendens). In the first experiment we tested the effect of a progressive dose (five 0.04 mg) on aggressive display with exposure to a mirror, whereas in the second experiment we tested the effect of an acute dose (0.2 mg) on the aggressive display with exposure to a mirror. The experiments were performed on 5 consecutive sessions at intervals of 18 hours between sessions. Differences of performance were shown by subjects in the acute and progressive treatments when compared with a control treatment in the majority of behaviors evaluated, namely Floating, Slow Swimming, Wavy Swimming, Emerging, Bend, Square Move and Motor Display Components. Acute treatment was different from control only on Show Body, while the progressive group differed on Resting, Horizontal Display and Appropriate Display Components. Differences between Correlate Display Components and Total were also shown. Both the acute and progressive contamination with HgCl2 decrease the motor activity in the aggressive display, mirror-image test of Betta splendens, mainly on the progressive dose. This implies an impairment on feeding behavior, predator avoidance, reproductive behavior, mate choice and territoriality. These results suggest that in this fish species, the progressive dose has a greater effect on behavior in general and that both the acute and progressive contamination with mercury chloride affect many other aspects of behavior.
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Elevated carbon dioxide (CO(2)) has recently been shown to affect chemosensory and auditory behaviour, and activity levels of larval reef fishes, increasing their risk of predation. However, the mechanisms underlying these changes are unknown. Behavioural lateralization is an expression of brain functional asymmetries, and thus provides a unique test of the hypothesis that elevated CO(2) affects brain function in larval fishes. We tested the effect of near-future CO(2) concentrations (880 µatm) on behavioural lateralization in the reef fish, Neopomacentrus azysron. Individuals exposed to current-day or elevated CO(2) were observed in a detour test where they made repeated decisions about turning left or right. No preference for right or left turns was observed at the population level. However, individual control fish turned either left or right with greater frequency than expected by chance. Exposure to elevated-CO(2) disrupted individual lateralization, with values that were not different from a random expectation. These results provide compelling evidence that elevated CO(2) directly affects brain function in larval fishes. Given that lateralization enhances performance in a number of cognitive tasks and anti-predator behaviours, it is possible that a loss of lateralization could increase the vulnerability of larval fishes to predation in a future high-CO(2) ocean.
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We investigated turning responses in 16 species of fish faced with a vertical-bar barrier through which a learned dummy predator was visible. Ten of these species showed a consistent lateral bias to turn preferentially to the right or to the left. Species belonging to the same family showed similar directions of lateral biases. We performed an independent test of shoaling tendency and found that all gregarious species showed population lateralisation, whereas only 40% of the non-gregarious species did so. The results provide some support to the Rogers (1989) hypothesis that population lateralisation might have been developed in relation to the need to maintain coordination among individuals in behaviours associated with social life.
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Cerebral lateralization refers to the division of information processing in either hemisphere of the brain and is a ubiquitous trait among vertebrates and invertebrates. Given its widespread occurrence, it is likely that cerebral lateralization confers a fitness advantage. It has been hypothesized that this advantage takes the form of enhanced cognitive function, potentially via a dual processing mechanism whereby each hemisphere can be used to process specific types of information without contralateral interference. Here, we examined the influence of lateralization on problem solving by Australian parrots. The first task, a pebble-seed discrimination test, was designed for small parrot species that feed predominately on small seeds, which do not require any significant manipulation with the foot prior to ingestion. The second task, a string-pull problem, was designed for larger bodied species that regularly use their feet to manipulate food objects. In both cases, strongly lateralized individuals (those showing significant foot and eye biases) outperformed less strongly lateralized individuals, and this relationship was substantially stronger in the more demanding task. These results suggest that cerebral lateralization is a ubiquitous trait among Australian parrots and conveys a significant foraging advantage. Our results provide strong support for the enhanced cognitive function hypothesis.
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The occurrence of functional left-right cerebral asymmetries has been documented in a wide range of animals, suggesting that the lateralization of cognitive functions enjoys some kind of selective advantage over the bilateral control of the same functions. Here, we compared schooling performance of fishes with high or low degree of lateralization, which were obtained through selective breeding. Schools of lateralized fishes moving in a novel environment showed significantly more cohesion and coordination than schools of non-lateralized (NL) fishes. Pairs of fishes lateralized in opposite directions were as efficient as pairs of same laterality, suggesting that the performance of lateralized fishes derives from a computational advantage rather than being the consequence of a behavioural similarity among schoolmates. In schools composed of both lateralized and NL fishes, the latter were more often at the periphery of the school while lateralized fishes occupied the core, a position normally safer and energetically less expensive.
Book
Human-induced environmental change currently represents the single greatest threat to global biodiversity. Species are typically adapted to the local environmental conditions in which they have evolved. Changes in environmental conditions initially influence behaviour, which in turn affects species interactions, population dynamics, evolutionary processes and, ultimately, biodiversity. How animals respond to changed conditions, and how this influences population viability, is an area of growing research interest. Yet, despite the vital links between environmental change, behaviour, and population dynamics, surprisingly little has been done to bridge these areas of research. This is the first book of its kind devoted to understanding behavioural responses to environmental change. The volume is comprehensive in scope, discussing impacts on both the mechanisms underlying behavioural processes, as well as the longer-term ecological and evolutionary consequences. Drawing on international experts from across the globe, the book covers topics as diverse as endocrine disruption, learning, reproduction, migration, species interactions, and evolutionary rescue.
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Selective serotonin reuptake inhibitors, such as fluoxetine, within the aquatic environment may adversely affect the health and behavior of exposed organisms. Most studies on the effects of inadvertent pharmaceutical exposure focus on the individual level rather than examining behavior within a network of individuals. Within communication networks, interactants send signals to multiple individuals, potentially altering, and being altered by, the behavior of nearby individuals. To address if fluoxetine interferes with communication within a network, male Siamese fighting fish interacted under three audience types (male, female, or no audience) and two exposure conditions (control, fluoxetine). In the control group, findings were similar to prior studies, with males altering gill flaring rate depending on the sex of the audience present. In the exposed group, gill flaring did not differ based on audience type and was lower overall compared to the control, suggesting a reduction in aggression. In contrast, both unexposed and exposed males performed more tail beats when a female audience was present, suggesting that fluoxetine has a context-specific effect on behavior. Behavioral changes during current interactions may affect behavior during later interactions as well as the outcome of future encounters with audience individuals. The influence of fluoxetine on total behavior within an interaction and loss of audience effect suggests it may generate broader changes in communication beyond the exposed individual, causing fitness consequences. This study stresses the importance of studying the effects of inadvertent pharmaceutical exposure on behavior in multiple social contexts to better understand its impacts on complex communication systems.
Article
A preference for the left-eye use during aggressive interactions has been widely reported in the literature, even though in some cases the direction of lateralization varies among individuals within populations. Laterality of aggression in male Siamese fighting fish has been described in a number of studies, yet very little is known about lateralization of aggression during reproduction and/or parental care in fish. Here, we aimed to investigate the relationship between the different reproductive phases and lateralization in eye use during aggressive interactions in males of Siamese fighting fish. Lateralization in eye use is influenced during the early reproductive state, before and after the bubble nest construction stages. We found that nest-holding males preferentially used the right eye before and after bubble nest construction independent of the sex of the intruder. During the later reproductive phases, aggressiveness increased whereby the direction of lateralization rather than the degree was influenced supporting the hypothesis that reproductive state influences behavioral consistency in Siamese fighting fish.
Article
Aggression plays an important role in survival and reproduction. It can be measured using mirror and dyadic tests, but there is some debate about whether interactions with a mirror image and with a real opponent measure the same aspects of aggressiveness. Variation in aggressiveness among individuals has been linked to behavioural lateralization. Lateralization, the preference for one side of the body over the other, has been reported widely in vertebrates. During aggression, individuals may use their right or left eye to view their opponent, but results vary among vertebrates; while some show a left-eye preference, others show a right-eye preference, with some individuals being more strongly lateralized than others within a population. In this study, we determined whether adult male and female zebrafish, Danio rerio, showed similar levels of aggression towards a mirror image as towards an opponent, and whether there were differences in eye use when the fish displayed aggressive behaviours. We found no difference in the rate of aggression shown towards a mirror image and an opponent, indicating that both tests are representative of the same measure. Furthermore, the sex of the zebrafish and the aggression test they experienced had a significant effect on eye use. Eye use by the females when viewing their opponent was similar to that of the males when they viewed an image and an opponent, but males used their left eye more.
Article
The increasing presence of aquatic contami-nants, such as the pharmaceutical fluoxetine, has raised concerns over potentially disrupting effects on several aspects of fish reproduction. However, the effects of flu-oxetine on reproductive and paternal behavior in fish remain understudied, particularly at environmentally rele-vant concentrations. In the current study, we therefore tested the hypothesis that waterborne fluoxetine at an environmentally relevant concentration (540 ng/l), disrupts specific reproductive and paternal behaviors in male Sia-mese fighting fish at distinct reproductive phases. A pre-post test design was adopted to investigate specific behavioral responses at the individual fish level in response to male conspecific intruders at two different distances from the nest across four distinct reproductive phases (before bubblenest construction, following bubblenest construction, after spawning and after hatching of the lar-vae). In the control specimens, the measured behaviours were not different between the spawning times and among the interactions in either distance to nest at the different reproduction phases. Our results indicate that fluoxetine specifically disrupts characteristic paternal territorial aggression behaviour only after spawning and hatching of the larvae, while male behaviour in previous reproductive phases is unaffected by fluoxetine exposure. Results of comparison between males at 1st spawning and specimens exposed to fluoxetine at 2nd spawning showed that the first reaction of the nest-holding males to the intruders, duration of fin spreading, number of bites, and 90° turn, and the frequency of sweeps were different between the spawning times after spawning or hatching of embryos. However, interaction of spawning time and reproduction phase was significant on biting behaviour. These results demonstrate that fluoxetine exposure at environmental concentrations negatively affects territorial defense behaviour in fighting fish during parental care after larval hatching, which may have possible implications on reproductive success and population dynamics.
Chapter
In the second edition of this fascinating book an international team of experts have been brought together to explore all major areas of fish learning, including: Foraging skills. Predator recognition. Social organisation and learning. Welfare and pain. Three new chapters covering fish personality, lateralisation, and fish cognition and fish welfare, have been added to this fully revised and expanded second edition. Fish Cognition and Behavior, Second Edition contains essential information for all fish biologists and animal behaviorists and contains much new information of commercial importance for fisheries managers and aquaculture personnel. Libraries in all universities and research establishments where biological sciences, fisheries and aquaculture are studied and taught will find it an important addition to their shelves.
Article
Due to the potential for long-term, low-level exposure of environmental species to pharmaceuticals in the environment, concerns over chronic ecotoxicity have been raised. Pharmaceuticals typically have specific enzyme and receptor-based modes of action, which are extensively studied in mammals during drug development. A survey of the literature demonstrated that there is conservation of many enzyme/receptor systems between mammalian and teleost systems. Based on this conservation of enzyme/receptor systems across teleost species, a model has been developed to utilize the information from mammalian pharmacology and toxicology studies to evaluate the potential for chronic receptor mediated responses in fish. In this model, a measured human therapeutic plasma concentration (HTPC) is compared to a predicted steady state plasma concentration (FSSPC) in fish, and an effect ratio (ER = HTPC/FSSPC) is computed. The lower the ER, the greater the potential for a pharmacological response in fish. Data collection and model validation will strengthen the applicability of this approach as a viable tool for prioritizing research initiatives that examine the potential impact of pharmaceuticals on fish.
Article
Cerebral lateralization refers to the lateralized partitioning of cognitive function in either hemisphere of the brain. Using a standard detour test, we investigated lateralized behaviour in wild-caught, female poeciliid fish, Brachyraphis (=Brachyrhaphis) episcopi, from high- and low-predation areas. Wild fish were bred and their offspring reared under controlled laboratory conditions. These laboratory-reared fish were screened in the same laterality assays as their parents. We observed differences between wild-caught females and their laboratory-reared female offspring in the pattern of lateralization (tendency to use one hemisphere over the other to process information). Conversely, the strength of lateralization (consistency of hemispherical bias) was largely conserved between generations, consistent with it being a heritable character. Both wild-caught females from high-predation sites and their laboratory-reared offspring showed stronger lateralized behaviour than their counterparts from low-predation sites. This difference in strength of lateralization is likely to provide fitness benefits to fish that occur in high-predation areas by enabling them to school and watch for predators simultaneously (dual processing). We hypothesized that the differences in the pattern of lateralization observed between species, and populations within species, are due to the manner in which they perceive and classify stimuli in the world around them. In particular, the perceived emotive content or context of a scene is likely to vary between individuals that have had different life experiences.
Article
A small but taxonomically diverse number of vertebrates have a left-eye preference for aggression, but this has been shown only in males. Here we present data consistent with a left-eye preference for aggressive rejection display in females of the striped plateau lizard, Sceloporus virgatus. Already-mated females perform this display, which contains key elements of male–male aggressive displays, to courting males. Lateral eye placement reduces binocular vision of such displays. In a field study, we recorded the responses of individual gravid females to one of three possible stimulus presentations: a tethered conspecific male presented so the female viewed him (1) from a head-on (HO) position, (2) with her left visual field (LVF) or (3) with her right visual field (RVF). Although a small proportion of all trials yielded no response, females were significantly less likely to show any response in RVF presentations compared with HO or LVF presentations. In a large majority of trials, females responded to males, and almost all responding females displayed aggressively. When females displayed after RVF presentations, a female was equally likely to use her LVF or RVF to view the male when she first performed an aggressive rejection display. In contrast, in LVF and HO presentations where females displayed, females were significantly more likely than expected by chance to use their LVF to view the males when they displayed. Charge, a very aggressive act, also was significantly more likely to occur when females were viewing males with their LVF than their RVF or HO. Finally, in a small number of unmanipulated natural encounters we observed, all females used their LVF to display to courting males. Our results suggest that, as in males of several vertebrate species, females show a left-eye bias for conspecific aggression.
Article
The advent of increasingly stringent and wider ranging European Union legislation relating to water and the environment has required regulators to assess compliance risk and to respond by formulating appropriate pollution control measures. To support this process the UK Water Industry has completed a national Chemicals Investigation Programme (CIP), to monitor over 160 wastewater treatment works (WwTWs) for 70 determinands. Final effluent concentrations of zinc, polynuclear aromatic hydrocarbons (fluoranthene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene and indeno(1,2,3-cd)pyrene), "penta" congeners (BDEs) 47 and 99, tributyltin, triclosan, erythromycin, oxytetracycline, ibuprofen, propranolol, fluoxetine, diclofenac, 17β-estradiol and 17α-ethinyl estradiol exceeded existing or proposed Environmental Quality Standards (EQSs) in over 50% of WwTWs. Dilution by receiving water might ensure compliance with EQSs for these chemicals, apart from the BDEs. However, in some cases there will be insufficient dilution to ensure compliance and additional management options may be required.
Chapter
IntroductionLateralized functions in fishIndividual differences in lateralizationEcological consequences of lateralization of cognitive functionsSummary and future researchAcknowledgementsReferences
Article
The detrimental effects of steroid-mimics are well known but investigations on non-steroid pharmaceuticals are less common. In addition, most behavioral studies do not examine the effects at multiple time points. This study examined the effects of fluoxetine, a selective serotonin reuptake inhibitor, on behavior when male Siamese fighting fish encounter female and male dummy conspecifics simultaneously. Thus, how chemical exposure impacts behavioral consistency and whether individuals differ in their sensitivity to exposure was assessed. Overall aggression was reduced after fluoxetine administration while courtship was unaffected. Fluoxetine affected behavioral consistency towards both the male and female, with individuals behaving less consistently to the male and more consistently to the female. In addition, males appeared to differ in their sensitivity to fluoxetine exposure as not all males reduced their aggression after administration. This has important implications for studying the effects of unintended pharmaceutical exposure. Exposure may have evolutionary implications as it may influence both territorial defense and mating success. In sum, these findings demonstrate that pharmaceutical exposure may alter more than just overall level of behavior and stress the importance of examining the effects of exposure on an individual level.
Article
Serotonin (5-HT) and norepinephrine (NE) innervate both the left and right hemispheres of the brain, but whether they affect lateralization of function is unknown. This paper concisely examines evidence that these two neurotransmitters differentially affect the two hemispheres, and puts forth the novel hypothesis 5-HT preferentially activates the right hemisphere (RH) and NE the left hemisphere (LH). The principal lines of evidence comprise studies of: (1) 5-HT and NE level measurement, (2) receptor binding, (3) functional brain imaging, (4) dichotic listening, and (5) electroencephalography and evoked potentials. In assessing these 5 lines, emphasis is placed on studies of pharmaceutical drugs that affect the 5-HT and NE systems. While all of the data do not support the hypothesis, they are generally consistent with it, or a variant of the hypothesis that there is a bias toward 5-HT preferentially activating a majority of brain areas or functions in the RH, and NE a majority of LH areas or functions. If this hypothesis, or a variant of it, is correct, it may be relevant to understanding the physiological basis of neuropsychiatric disorders that could involve dysfunction in brain monoaminergic systems, as well as understanding potential lateralization of the effects of drugs that act on these systems.
Article
The display of 24 individual male Siamese fighting fish to an unresponsive stimulus conspecific was measured, and the fish were then placed together in pairs. For 11 of the 12 pairs, the outcome of the aggressive interaction which ensued was predicted by the gill cover erection durations obtained in the pre-fight isolate tests. The implications of this result for theories of display function are discussed.
Article
For red deer stags, fighting both has appreciable costs and yields considerable benefits. Up to 6% of rutting stags are permanently injured each year, while fighting success and reproductive success are closely related, within age groups as well as across them. Fighting behaviour is sensitive to changes in the potential benefits of fighting: stags fight most frequently and most intensely where potential benefits are high and tend to avoid fighting with individuals they are unlikely to beat. The relevance of these findings to theoretical models of fighting behaviour is discussed.
Article
In Ostariophysan fish, the detection of the alarm substance liberated into the water as a consequence of an attack by a predator elicits an alarm reaction or anti-predatory behavior. In this study, experiments were performed to: (i) describe and quantitatively characterize the behavioral and ventilatory responses in piauçu fish (Leporinus macrocephalus), individually and as part of a school, to conspecific alarm substance (CAS) and; (ii) test the effect of acute fluoxetine treatment on alarm reaction. Histological analysis revealed the presence of club cells in the intermediate and superficial layers of the epidermis. The predominant behavioral response to CAS was freezing for fish held individually, characterized by the cessation of the swimming activity as the animal settles to a bottom corner of the aquarium. Fish exposed to CAS showed decrease in the mean ventilatory frequency (approximately 13%) relative to control. In schools, CAS elicited a biphasic response that was characterized by erratic movements followed by increased school cohesion and immobility, reflected as an increased school cohesion (65.5% vs. -5.8% for controls) and in the number of animals near the bottom of the aquarium (42.0% vs. 6.5% for controls). Animals treated with single i.p. injections of fluoxetine (10 μg/g b.w.) did not exhibit alarm behavior following CAS stimulation. These results show that an alarm pheromone system is present in piauçu fish, evidenced by the presence of epidermal club cells and an alarm reaction induced by CAS and consequently of a chemosensory system to transmit the appropriate information to neural structures responsible for initiating anti-predator behavioral responses. In addition, fluoxetine treatment caused an anxiolytic-like effect following CAS exposure. Thus, the alarm reaction in piauçu can be a useful model for neuroethological and pharmacological studies of anxiety-related states.
Article
Neurons using serotonin (5-HT) as neurotransmitter and/or modulator have been identified in the central nervous system in representatives from all vertebrate clades, including jawless, cartilaginous and ray-finned fishes. The aim of this review is to summarize our current knowledge about the anatomical organization of the central serotonergic system in fishes. Furthermore, selected key functions of 5-HT will be described. The main focus will be the adult brain of teleosts, in particular zebrafish, which is increasingly used as a model organism. It is used to answer not only genetic and developmental biology questions, but also issues concerning physiology, behavior and the underlying neuronal networks. The many evolutionary conserved features of zebrafish combined with the ever increasing number of genetic tools and its practical advantages promise great possibilities to increase our understanding of the serotonergic system. Further, comparative studies including several vertebrate species will provide us with interesting insights into the evolution of this important neurotransmitter system.
Article
Fluoxetine (FLX) is a pharmaceutical acting as a selective serotonin reuptake inhibitor and is used to treat depression in humans. Fluoxetine and the major active metabolite norfluoxetine (NFLX) are released to aquatic systems via sewage-treatment effluents. They have been found to bioconcentrate in wild fish, raising concerns over potential endocrine disrupting effects. The objective of this study was to determine effects of waterborne FLX, including environmental concentrations, on the reproductive axis in sexually mature male goldfish. We initially cloned the goldfish serotonin transporter to investigate tissue and temporal expression of the serotonin transporter, the FLX target, in order to determine target tissues and sensitive exposure windows. Sexually mature male goldfish, which showed the highest levels of serotonin transporter expression in the neuroendocrine brain, were exposed to FLX at 0.54μg/L and 54μg/L in a 14-d exposure before receiving vehicle or sex pheromone stimulus consisting of either 4.3nM 17,20β-dihydroxy-4-pregnene-3-one (17,20P) or 3nM prostaglandin F₂(α) (PGF₂(α)). Reproductive endpoints assessed included gonadosomatic index, milt volume, and blood levels of the sex steroids testosterone and estradiol. Neuroendocrine function was investigated by measuring blood levels of luteinizing hormone, growth hormone, pituitary gene expression of luteinizing hormone, growth hormone and follicle-stimulating hormone and neuroendocrine brain expression of isotocin and vasotocin. To investigate changes at the gonadal level of the reproductive axis, testicular gene expression of the gonadotropin receptors, both the luteinizing hormone receptor and the follicle-stimulating hormone receptor, were measured as well as expression of the growth hormone receptor. To investigate potential impacts on spermatogenesis, testicular gene expression of the spermatogenesis marker vasa was measured and histological samples of testis were analyzed qualitatively. Estrogen indices were measured by expression and activity analysis of gonadal aromatase, as well as liver expression analysis of the estrogenic marker, esr1. After 14d, basal milt volume significantly decreased at 54μg/L FLX while pheromone-stimulated milt volume decreased at 0.54μg/L and 54μg/L FLX. Fluoxetine (54μg/L) inhibited both basal and pheromone-stimulated testosterone levels. Significant concentration-dependent reductions in follicle-stimulating hormone and isotocin expression were observed with FLX in the 17,20P- and PGF₂(α)-stimulated groups, respectively. Estradiol levels and expression of esr1 concentration-dependently increased with FLX. This study demonstrates that FLX disrupts reproductive physiology of male fish at environmentally relevant concentrations, and potential mechanisms are discussed.
Article
It is well established that serotonin (5-HT; 5-hydroxytryptamine) plays a role in mammalian regulation of the hypothalamic-pituitary-adrenal (HPA) axis via the 5-HT receptor subtype 1A (5-HT(1A)). To date, there has not been a comprehensive investigation of the molecular, pharmacological and physiological aspects of the 5-HT(1A) receptor and its role in the activation of the hypothalamic-pituitary-interrenal (HPI) axis in teleost fish. The 5-HT(1A) receptor of the Gulf toadfish (Opsanus beta) was cloned and sequenced, showing 67.5% amino acid similarity to the human homologue. The 5-HT(1A) receptor was distributed throughout the brain, with the whole brain containing significantly higher levels of 5-HT(1A) mRNA compared to all other tissues and the midbrain/diencephalon region containing significantly higher levels of transcript than any other brain region. Substantial levels of transcript were also found in the pituitary, while very low levels were in the kidney that contains the interrenal cells. Xenopus oocytes injected with toadfish 5-HT(1A) receptor cRNA displayed significantly higher binding of [(3)H]5-HT that was abolished by the mammalian 5-HT(1A) receptor agonist, 8-OH-DPAT, indicating a conserved binding site of the toadfish 5-HT(1A) receptor and a high specificity for the agonist. Supporting this, binding of [(3)H]5-HT was not affected by the mammalian 5-HT(1B) receptor agonist, 5-nonyloxytryptamine, the 5-HT(7) receptor antagonist, SB269970, or the 5-HT(2) receptor agonist, alpha-methylserotonin. Confirming these molecular and pharmacological findings, intravenous injection of 8-OH-DPAT stimulated the HPI axis to cause a 2-fold increase in circulating levels of cortisol. The present study of the 5-HT(1A) receptor in a single teleost species illustrates the high conservation of this 5-HT receptor amongst vertebrates.
Article
In a variety of vertebrates, highly aggressive individuals tend to have high social status and low serotonergic function. In the sex changing fish Lythrypnus dalli, serotonin (5-HT) may be involved as a mediator between the social environment and the reproductive system because social status is a critical cue in regulating sex change. Subordination inhibits sex change in L. dalli, and it is associated with higher serotonergic activity in other species. We tested the hypothesis that high serotonergic activity has an inhibitory effect on sex change. In a social situation permissive to sex change, we administered to the dominant female implants containing the serotonin precursor 5-hydroxytryptophan (5-HTP). In a social situation not conducive to sex change, we administered either the serotonin synthesis inhibitor p-chlorophenylalanine (PCPA) or the 5-HT(1A) receptor antagonist p-MPPI. After three weeks we used HPLC to measure brain levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA). We also performed PCPA, p-MPPI and fluoxetine injections in size-matched pairs of females to assess its effect on dominance status. Males and newly sex changed fish showed a trend for higher levels of 5-HIAA and 5-HT/5-HIAA ratio than females. The different implants treatments did not affect the probability of sex change. Interestingly, this species does not seem to fit the pattern seen in other vertebrates where dominant individuals have lower serotonergic activity than subordinates.
Article
The experiment was performed in two phases. During the first phase (phase 1) the dominance hierarchy was determined in 4 groups of Arctic charr (Salvelinus alpinus L.), each group consisting of 4 fish. Phase 2 was started by rearranging phase 1 fish into 4 new groups. Group 1 consisted of previously dominant fish and groups 2, 3 and 4 of fish that previously held rank 2, 3 and 4, respectively. After phase 2 telencephalon and brain stem were analyzed with regard to their contents of serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), the principle metabolite of 5-HT. No correlation was found between the social rank (measured as dominance index) during phase 1 and the brain serotonergic activity (measured as the ratio 5-HIAA/5-HT) determined after phase 2. However, most important, the 5-HIAA/5-HT ratio was significantly correlated with the last experienced social rank, i.e. that acquired during phase 2. These results shows that the difference in brain serotonergic activity between dominant and subordinate fish develops through social interactions. Further, we found that previous subordinate experience inhibited aggressive behavior, an effect which, in the light of available information on stress and 5-HT, could be related to the increase in brain serotonergic activity. We hypothesize that stress induces an increased serotonergic activity which in turn inhibits the neuronal circuitry which mediates aggressive behavior.
Article
Evidence of lateral asymmetries in the direction of turning during escape behaviour in a species of poeciliid fish, Girardinus falcatus, is reported. When repeatedly faced with a simulated predator (in five successive sessions, spaced 7 days apart), immature Girardinus falcatus exhibited a significant population bias to turn right on the first session and a progressive bias to turn left in subsequent sessions. Mature Girardinus were then tested to check whether the shift in the direction of turn with repeated sessions depended on maturation or habituation. It was found that adult Girardinus showed a slight population bias to turn right in the first session and a strong subsequent bias to turn left after repeated sessions. The implications of these findings to our current understanding of the evolution of brain lateralization are discussed.
Article
The lateralized effects of ethanol (ETOH) upon behavior and monoamine biochemistry in the lizard, Anolis carolinensis, were examined. Eight adult male anoles consumed solutions of 19% ethanol (ETOH) twice daily over the course of 18 days, while controls consumed water. ETOH decreased the use of the left eye/right hemisphere, but not the right eye/left hemisphere, during territorial aggression (p<0.05). During crossover (i.e., ETOH to water and vice versa) this effect was reversible and replicable. Biochemically, an asymmetry was observed in 5-HT levels in the raphe both in ETOH and controls. ETOH increased levels of serotonin (5-HT; p<0.05), and 5-HIAA/5-HT ratios (p<0.05) in the raphe; serotonin levels in several brain regions correlated with aggressive responses. These results suggest that ETOH boosts 5-HT levels in animals subchronically exposed to ETOH. They further suggest that asymmetry in endogenous 5-HT systems may account for the asymmetrical regulation of aggression generally, and may explain the behavioral effects of ETOH upon lateralized aggression.
Article
It has recently been reported that predator inspection is more likely to occur when a companion (i.e. the mirror image of the test animal) is visible on the left rather than on the right side of mosquitofish Gambusia holbrooki. This very unexpected outcome could be consistent with the hypothesis of a preferential use of the right eye during sustained fixation of a predator as well as of a preferential use of the left eye during fixation of conspecifics. We measured the time spent in monocular viewing during inspection of their own mirror images in females of six species of fish, belonging to different families-G. holbrooki, Xenotoca eiseni, Phoxinus phoxinus, Pterophyllum scalare, Xenopoecilus sarasinorun, and Trichogaster trichopterus. Results revealed a consistent left-eye preference during sustained fixation in all of the five species. Males of G. holbrooki, which do not normally show any social behaviour, did not exhibit any eye preferences during mirror-image inspection. We found, however, that they could be induced to manifest a left-eye preference, likewise females, if tested soon after capture, when some affiliative tendencies can be observed. These findings add to current evidence in a variety of vertebrate species for preferential involvement of structures located in the right side of the brain in response to the viewing of conspecifics.
Article
The selective serotonin reuptake inhibitors (SSRIs) have become the most prescribed antidepressants in many countries. Although the SSRIs share a common mechanism of action, they differ substantially in their chemical structure, metabolism, and pharmacokinetics. Perhaps the most important difference between the SSRIs is their potential to cause drug-drug interactions through inhibition of cytochrome-P450 (CYP) isoforms. This paper provides an update on both the in vitro and in vivo evidence with respect to CYP-mediated drug-drug interactions with this class of antidepressants. The available evidence clearly indicates that the individual SSRIs display a distinct profile of cytochrome P450 inhibition. Fluvoxamine is a potent CYP1A2 and CYP2C19 inhibitor, and a moderate CYP2C9, CYP2D6, and CYP3A4 inhibitor. Fluoxetine and paroxetine are potent CYP2D6 inhibitors, whereas fluoxetine's main metabolite, norfluoxetine, has a moderate inhibitory effect on CYP3A4. Sertraline is a moderate CYP2D6 inhibitor; citalopram appears to have little effect on the major CYP isoforms. Fluoxetine deserves special attention as inhibitory effects on CYP-activity can persist for several weeks after fluoxetine discontinuation because of the long half-life of fluoxetine and its metabolite norfluoxetine. Drug combinations with SSRIs should be assessed on an individual basis. Knowledge regarding the CYP-isoforms involved in the metabolism of the co-administered drug may help clinicians to anticipate and avoid potentially dangerous drug-drug interactions. Anticipated interactions can usually be managed by appropriate dose adjustment and titration of the object drug. In some cases, therapeutic drug monitoring can be useful. Equally well, an SSRI with limited interaction potential may be selected to treat depression in patients that receive other medications.
Article
Recent research has suggested that lateralization of aggressive behaviors could follow an homogeneous pattern among all vertebrates. A left eye/right hemisphere dominance in eliciting aggressive responses has been demonstrated for all groups of tetrapods but teleost fish for which data is lacking. Here we studied differential eye use during aggressive interactions in three species of teleosts: Gambusia holbrooki, Xenotoca eiseni and Betta splendens. In the first experiment we checked for lateralization in the use of the eyes while the subject was attacking its own mirror image. In order to confirm the results, other tests were performed on two species and eye preference was scored during attacks or displays directed toward a live rival. All three species showed a marked preference for using the right eye when attacking a mirror image or a live rival. Thus, the direction of asymmetry in fish appears the opposite to that shown by all the other groups of vertebrates. Hypotheses on the origin of the difference are discussed.
Article
This study investigated how parental care increases with offspring age by examining the level of male aggressiveness toward potential intruders during egg guarding in a natural population of Siamese fighting fish (Betta splendens Regan). The degree of aggressiveness was measured at two reproductive phases in response to three types of intruders: male, female and females that have laid eggs. The nest-holding males became more aggressive after their eggs hatched than after the eggs were laid. Nest-holding males displayed gill cover erection, biting, tail beating and attacking at the highest rate towards male intruders, intermediate towards female intruders and the least aggressive towards females, which have laid eggs.
Article
Left- and right-monocular viewing during inspection of their own mirror-image was measured in fish (Xenopoecilus sarasinorum) that had been kept for 20 days in a tank with a mirror or in a tank in which conspecifics were visible behind a transparent glass partition. Results revealed a preferential use of the monocular visual field of the left eye in both conditions. The asymmetry was stronger during the first 5 min of observation and tended to fade slightly thereafter. In a second experiment left- and right-monocular viewing was measured in presence of artificial stimuli. Fish were kept for 20 days in a tank with either horizontal or vertical stripes positioned along one wall and then tested for eye use in a tank with a familiar (same orientation) or an unfamiliar (different orientation) pattern of stripes. Fish showed a preferential use of the monocular field of the left eye when presented with the familiar pattern and a slight preferential use of the right eye with the unfamiliar pattern. The former bias was stronger in the first minutes of test, after which it tended first to reverse and then to fade away; the latter bias, in contrast, appeared only after some minutes of observation. It is argued that the preferential use of the monocular visual field of the left eye (mainly serving structures located to the right side of the encephalon) is probably part of a more general specialization to establish identity, i.e. that an apparently familiar stimulus is indeed identical with one previously experienced. Preferential use of the monocular field of the right eye, in contrast, is argued to be associated with visual control of response.
Article
Low levels of human medicines (pharmaceuticals) have been detected in many countries in sewage treatment plant (STP) effluents, surface waters, seawaters, groundwater and some drinking waters. For some pharmaceuticals effects on aquatic organisms have been investigated in acute toxicity assays. The chronic toxicity and potential subtle effects are only marginally known, however. Here, we critically review the current knowledge about human pharmaceuticals in the environment and address several key questions. What kind of pharmaceuticals and what concentrations occur in the aquatic environment? What is the fate in surface water and in STP? What are the modes of action of these compounds in humans and are there similar targets in lower animals? What acute and chronic ecotoxicological effects may be elicited by pharmaceuticals and by mixtures? What are the effect concentrations and how do they relate to environmental levels? Our review shows that only very little is known about long-term effects of pharmaceuticals to aquatic organisms, in particular with respect to biological targets. For most human medicines analyzed, acute effects to aquatic organisms are unlikely, except for spills. For investigated pharmaceuticals chronic lowest observed effect concentrations (LOEC) in standard laboratory organisms are about two orders of magnitude higher than maximal concentrations in STP effluents. For diclofenac, the LOEC for fish toxicity was in the range of wastewater concentrations, whereas the LOEC of propranolol and fluoxetine for zooplankton and benthic organisms were near to maximal measured STP effluent concentrations. In surface water, concentrations are lower and so are the environmental risks. However, targeted ecotoxicological studies are lacking almost entirely and such investigations are needed focusing on subtle environmental effects. This will allow better and comprehensive risk assessments of pharmaceuticals in the future.