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The zebrafish (Danio rerio, Hamilton, 1822) is one of the most important fish model species in scientific research, with millions of fish housed in laboratory animal facilities around the world. During husbandry, it is necessary to regularly handle the fish, which could cause short‐ and long‐term stress, possibly affecting both fish welfare and experimental outcomes. In two experiments, the authors studied effects of transferring adult zebrafish, by chasing them with a net and/or exposing them to air (netting) on different endpoints: cortisol levels, reproduction parameters and behavioural parameters. They used realistic chase and air‐exposure times to mimic normal zebrafish husbandry and investigated the potential to habituate to handling stressors. Finally, the potential welfare improvements of a nutritional reward after handling were studied. All types of handling induced a stress response, but the authors did not find a correlation with the intensity of the stressor. Realistic (short) handling routines also caused stress, both after the first time and after regular handling over a long period of time. Cortisol levels peaked after 15 min, were still elevated after 30 min and dropped to resting level after 60 min. This should be taken into account by researchers when carrying out measurements or behavioural trials within an hour after handling. There is a minor potential benefit of nutritional rewards that may contribute to a faster recovery of normal behaviour. They did not find evidence of habituation to chasing and netting stress. Taking the stress response after handling into consideration will improve fish welfare and health and minimise husbandry‐associated sources of variation. [ABSTRACT FROM AUTHOR]

• No interactive effects of 3,4-DCA exposure and increased temperature emerged. • We found a negative effect of 3,4-DCA on thermal tolerance. • This is relevant in light of increasing temperatures under climate change. Although aquatic organisms are increasingly exposed to pollutants and abnormally high temperatures as a consequence of climate change, interactive effects between those stressors remain poorly assessed. Especially in ectotherms, such as fish, increases in ambient temperature are expected to affect fitness-related traits and physiology. We used the turquoise killifish Nothobranchius furzeri to study the effects of a range of 3,4-dichloroaniline concentrations (0, 50, 100 μg/L) in combination with two temperature conditions (control and control +4 °C) during four months of exposure. As part of an integrated multi-level approach, we quantified effects on classic life history traits (size, maturation time, body mass, fecundity), critical thermal maximum and physiology (energy reserves and stress-associated enzymatic activity). While no interactive effects of 3,4-DCA exposure and increased temperature emerged, our results do show a negative effect of 3,4-DCA on thermal tolerance. This finding is of particular relevance in light of increasing temperatures under climate change. Due to increases in pest species and faster degradation of 3,4-DCA under higher temperatures, increased use of the pesticide is expected under climate change which, in turn, could result in a decreased tolerance of aquatic organisms to high temperatures. [ABSTRACT FROM AUTHOR]

Pesticides are crucial to improve agricultural productivity, but often adversely affect surrounding aquatic systems and their fauna. To determine the environmental risk of pesticides, routine ecotoxicological tests are performed on several organisms, including standard fish models. However, these typically do not include fish species from variable habitats and with non-generic life-histories. In particular, inhabitants from temporary ponds such as annual killifish are conventionally understood to be resilient to natural stressors which could translate to higher pesticide resistance or, alternatively, trade-off with their resistance to pesticides and render them more sensitive than classic fish models. Using standard exposure tests, we assessed short-term toxicity effects of two commonly used pesticides, Roundup and cypermethrin, on the annual killifish Nothobranchius neumanni, and compared its sensitivity with that of classic fish models. For Roundup, we found a 72 h-LC 50 of 1.79 ± 0.11 mg/L, which is lower than the values reported for zebrafish, medaka, fathead minnow and rainbow trout, suggesting that N. neumanni is more sensitive to the compound. The opposite was true for cypermethrin, with a 72 h-LC 50 of 0.27 ± 0.03 mg/L. However, these LC 50 -values do not deviate strongly from those reported for other fish species, supporting earlier findings in the congeneric N. furzeri that the sensitivity of annual killifish to pollutants is similar to that of classic fish models despite their assumed robustness to environmental stress. [Display omitted] • Fish with non-generic life-histories are seldom included in ecotoxicological tests. • Sensitivity of N. neumanni to Roundup was higher than in classic fish models. • Sensitivity to cypermethrin was lower compared to classic fish models. • Overall, killifish sensitivity to pollutants is in line with that of other fish species. [ABSTRACT FROM AUTHOR]

As many freshwaters are chemically polluted, one of the challenges for policy makers is to determine the potential impact of these pollutants on ecosystems and to define safe concentrations. Common practice is the use of ecotoxicological assays to assess the response of model organisms from different trophic levels such as algae, invertebrates and fish during exposure to dilutions of a specific compound. Ideally, ecotoxicological assessments of (pseudo-)persistent chemicals should be performed across the life-cycle or even multiple generations for an accurate risk assessment. Multigenerational tests with fish are, however, impractical and costly given the long lifespan and generation time of classic model species. Here, we suggest a framework for more relevant, time- and cost-efficient fish-based testing in ecotoxicology and align it with accredited test guidelines. Next, we introduce an upcoming fish model, the turquoise killifish Nothobranchius furzeri, and show how it facilitates such research agendas due to a short lifespan and generation time. Through a review of fish-based exposure studies with a set of reference toxicants, we position N. furzeri as a sensitive species, suitable for screening effects of different pollutant types. Ultimately, we perform a cost-benefit analysis and propose a plan of action for the introduction of N. furzeri into accredited test guidelines. • We provide an overview of current issues with fish-based testing in ecotoxicology. • We suggest a framework for relevant, time- and cost-efficient fish-based testing. • We showcase killifish as a sensitive model for chronic and multigenerational tests. • We identify future research perspectives to integrate the model in accredited tests. [ABSTRACT FROM AUTHOR]

Pharmaceuticals are essential for human well‐being, but their increasing and continuous use pollutes the environment. Although behavioral ecotoxicology is increasingly advocated to assess the effects of pharmaceutical pollution on wildlife and ecosystems, a consensus on the actual environmental risks is lacking for most compounds. The main limitation is the lack of standardized reproducible tests that are based on sensitive behavioral endpoints and that accommodate a high ecological relevance. In the present study, we assessed the impact of a 3‐wk exposure to the antidepressant fluoxetine on multiple behavioral traits in the promising new model organism Nothobranchius furzeri (turquoise killifish). Overall, our study shows that fluoxetine can impact feeding behavior, habitat choice in a novel environment, and antipredator response of N. furzeri individuals; effects on spontaneous activity and exploration tendency were less pronounced. However, effects became only apparent when individuals were exposed to fluoxetine concentrations that were 10 times higher than typical concentrations in natural aquatic environments. Ecotoxicologists are challenged to maximize both the reliability and ecological validity of risk assessments of pollutants. Our study contributes to the development of a time‐ and cost‐efficient, standardized ecotoxicological test based on sensitive, ecologically relevant behavioral endpoints in N. furzeri. Environ Toxicol Chem 2019;38:262–270. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Abstract: In the animal kingdom, behavioral variation among individuals has often been reported. However, stable among‐individual differences along a behavioral continuum—reflective of personality variation—have only recently become a key target of research. While a vast body of descriptive literature exists on animal personality, hypothesis‐driven quantitative studies are largely deficient. One of the main constraints to advance the field is the lack of suitable model organisms. Here, we explore whether N. furzeri could be a valuable model to bridge descriptive and hypothesis‐driven research to further unravel the causes, function and evolution of animal personality. As a first step toward this end, we perform a common garden laboratory experiment to examine if behavioral variation in the turquoise killifish Nothobranchius furzeri reflects personality divergence. Furthermore, we explore if multiple behavioral traits are correlated. We deliver “proof of principle” of personality variation among N. furzeri individuals in multiple behavioral traits. Because of the vast body of available genomic and physiological information, the well‐characterized ecological background and an exceptionally short life cycle, N. furzeri is an excellent model organism to further elucidate the causes and implications of behavioral variation in an eco‐evolutionary context. [ABSTRACT FROM AUTHOR]

Abstract: Both constitutive and inducible antipredator strategies are ubiquitous in nature and serve to maximize fitness under a predation threat. Inducible strategies may be favored over constitutive defenses depending on their relative cost and benefit and temporal variability in predator presence. In African temporary ponds, annual killifish of the genus Nothobranchius are variably exposed to predators, depending on whether larger fish invade their habitat from nearby rivers during floods. Nonetheless, potential plastic responses to predation risk are poorly known. Here, we studied whether Nothobranchius furzeri individuals adjust their life history in response to a predation threat. For this, we monitored key life history traits in response to cues that signal the presence of predatory pumpkinseed sunfish (Lepomis gibbosus). While growth rate, adult body size, age at maturation, and initial fecundity were not affected, peak and total fecundity were higher in the predation risk treatment. This contrasts with known life history strategies of killifish from permanent waters, which tend to reduce reproduction in the presence of predators. Although our results show that N. furzeri individuals are able to detect predators and respond to their presence by modulating their reproductive output, these responses only become evident after a few clutches have been deposited. Overall our findings suggest that, in the presence of a predation risk, it can be beneficial to increase the production of life stages that can persist until the predation risk has faded. [ABSTRACT FROM AUTHOR]

• Multigenerational mixed-stressor impact is not routinely studied in ecotoxicology. • Life-cycle and multigenerational tests are inefficient with standard fish models. • Such studies are possible in under 6 months with turquoise killifish. • Antidepressant and pesticide effects differ in single vs. combined treatments. • Antidepressant and pesticide effects differ across successive generations. Ecological risks of a pollutant are typically assessed via short-term exposure of model organisms to that single compound. Such tests are informative, but cannot ascertain effects of long-term and multigenerational mixed-stressor exposure with which organisms are often confronted in their natural environment. Therefore, full life-cycle and multigenerational tests are needed. Yet, these are hampered due to long lifespans and generation times of many standard laboratory species, in particular for vertebrates such as fish. With a typical lifespan of 6 months and a generation time of about 3 months, the turquoise killifish (Nothobranchius furzeri) may be an ideal model for multigenerational testing. In this study, we assessed the impact of full life-cycle exposure to the emerging pollutant fluoxetine (0, 0.5 μg/L) in combination with chronic exposure during adulthood to the pesticide 3,4-dichloroaniline (0, 50, 100 μg/L) over two successive generations of N. furzeri. Overall, both life-history and behaviour were affected by exposure to fluoxetine and 3,4-DCA. Inhibitory effects of single chemical exposure on growth and fecundity were generation-dependent, while enhanced swimming acceleration and feeding in response to fluoxetine were dependent on the presence of 3,4-DCA. Together, these findings show the relevance of a multi-stressor approach across successive generations. Although full life-cycle and multigenerational tests are typically assumed to be impractical and costly for fish, we deliver an effective demonstration that such studies are possible within a timespan of less than 6 months with the killifish N. furzeri as a model organism. [ABSTRACT FROM AUTHOR]

Abstract: Freshwater organisms are increasingly exposed to combinations of stressors. However, because it is time‐consuming and costly, research on the interaction of stressors, such as compound toxicity and global warming on vertebrates, is scarce. Studies on multigenerational effects of these combined stressors are almost nonexistent. In the present study, we tested the combined effects of 4 °C warming and cadmium (Cd) exposure on life‐history traits, biomarkers, bioaccumulation, and multigenerational tolerance in the turquoise killifish, Nothobranchius furzeri. The extremely short life cycle of this vertebrate model allows for assessment of sublethal and multigenerational effects within 4 mo. The applied Cd concentrations had only limited effects on the measured endpoints, which suggests that N. furzeri is more resistant to Cd than fathead minnow and rainbow trout. In contrast, the temperature increase of 4 °C was stressful: it delayed female maturation and lowered adult mass and fecundity. Finally, indications of synergistic effects were found on peak fecundity and embryonic survival. Overall, these results indicate the importance of studying chronic and multigenerational effects of combined stressors. Environ Toxicol Chem 2018;37:2361–2371. © 2018 SETAC. [ABSTRACT FROM AUTHOR]