Fish self-awareness: limits of current knowledge and theoretical expectations.

Animal self-awareness is divided into three levels: bodily, social, and introspective self-awareness. Research has focused mainly on the introspection of so-called higher organisms such as mammals. Herein, we turn our attention to fish and provide opinions on their self-awareness based on a review of the scientific literature. Our specific aims are to discuss whether fish (A) could have a neural substrate supporting self-awareness and whether they display signs of (B) social and (C) introspective self-awareness. The present knowledge does not exclude the possibility that fish could have a simple neocortex or other structures that support certain higher cognitive processes, as the function of the primate cerebral cortex can be replaced by other neurological structures. Fish are known to display winner, loser, and audience effects, which could be interpreted as signs of social self-awareness. The audience effect may be explained not only by ethological cost and benefit theory but also by the concept of public self-awareness, which comes from human studies. The behavioural and neural manifestations of depression may be induced in fish under social subordination and may be viewed as certain awareness of a social status. The current findings on fish introspective self-awareness have been debated in the scientific community and, therefore, demand replication to provide more evidence. Further research is needed to verify the outlined ideas; however, the current knowledge indicates that fish are capable of certain higher cognitive processes, which raises questions and implications regarding ethics and welfare in fish-related research and husbandry.

Ferroptosis: A New Road towards Cancer Management.

Ferroptosis is a recently described programmed cell death mechanism that is characterized by the buildup of iron (Fe)-dependent lipid peroxides in cells and is morphologically, biochemically, and genetically distinct from other forms of cell death, having emerged to play an important role in cancer biology. Ferroptosis has significant importance during cancer treatment because of the combination of factors, including suppression of the glutathione peroxidase 4 (Gpx4), cysteine deficiency, and arachidonoyl (AA) peroxidation, which cause cells to undergo ferroptosis. However, the physiological significance of ferroptosis throughout development is still not fully understood. This current review is focused on the factors and molecular mechanisms with the diagrammatic illustrations of ferroptosis that have a role in the initiation and sensitivity of ferroptosis in various malignancies. This knowledge will open a new road for research in oncology and cancer management.

Theranostic Approach for the Protein Corona of Polysaccharide Nanoparticles.

Polysaccharide nanoparticles are promising materials in the wide range of disciplines such as medicine, nutrition, food production, agriculture, material science and others. They excel not only in their non-toxicity and biodegradability but also in their easy preparation. As well as inorganic particles, a protein corona (PC) around polysaccharide nanoparticles is formed in biofluids. Moreover, it has been considered that the overall response of the organism to nanoparticles presence depends on the PC. This review summarises scientific publications about the structural chemistry of polysaccharide nanoparticles and their impact on theranostic applications. Three strategies of implementation of the PC in theranostics have been discussed: I) Utilisation of the PC in therapy; II) How the composition of the PC is analysed for specific disease markers; III) How the formed PC can interact with the immune system and enhances the immunomodulation or immunoelimination. Thus, the findings from this review can contribute to improve the design of drug delivery systems. However, it is still necessary to elucidate the mechanisms of nano-bio interactions and discover new connections in nanoscale research.

Methamphetamine pollution elicits addiction in wild fish.

Illicit drug abuse presents pervasive adverse consequences for human societies around the world. Illicit drug consumption also plays an unexpected role in contamination of aquatic ecosystems that receive wastewater discharges. Here, we show that methamphetamine, considered as one of the most important global health threats, causes addiction and behavior alteration of brown trout Salmo trutta at environmentally relevant concentrations (1 µg l-1). Altered movement behavior and preference for methamphetamine during withdrawal were linked to drug residues in fish brain tissues and accompanied by brain metabolome changes. Our results suggest that emission of illicit drugs into freshwater ecosystems causes addiction in fish and modifies habitat preferences with unexpected adverse consequences of relevance at the individual and population levels. As such, our study identifies transmission of human societal problems to aquatic ecosystems.

Prescribed aggression of fishes: Pharmaceuticals modify aggression in environmentally relevant concentrations.

Traces of psychoactive substances have been found in freshwaters globally. Fish are chronically exposed to pollution at low concentrations. The changes of aggressive behaviour of chub (Squalius cephalus) were determined under the exposure to four psychoactive compounds (sertraline, citalopram, tramadol, methamphetamine) at environmentally relevant concentrations of 1 µg/L for 42 days. We tested whether (A) the behavioural effect of compounds varies within a single species; (B) there is a correlation between the individual brain concentration of the tested pollutants and fish aggression using the novel analysis of pollutants in brain; and (C) there is detectable threshold to effective pollutant concentration in brain. Behaviour and pollutant concentrations in brain were determined repeatedly (1st, 7th, 21st, 42nd and 56th days), including a two-week-long depuration period. The effect of particular compounds varied. Citalopram and methamphetamine generally increased the fish aggression, while no such effect was found after exposure to tramadol or sertraline. The longitudinal analysis showed an aggression increase after depuration, indicating the presence of withdrawal effects in methamphetamine- and tramadol-exposed fish. The analysis of pollutant concentration in brain revealed a positive linear relationship of citalopram concentration and aggression, while no such effect was detected for other compounds and/or their metabolites. Structural break analyses detected concentration thresholds of citalopram (1 and 3 ng/g) and sertraline (1000 ng/g) in brain tissue, from which a significant effect on behaviour was manifested. While the effect of sertraline was not detected using traditional approaches, there was a reduction in aggression after considering its threshold concentration in the brain. Our results suggest that pursuing the concentration threshold of psychoactive compounds can help to reduce false negative results and provide more realistic predictions on behavioural outcomes in freshwater environments, especially in the case of compounds with bioaccumulation potential such as sertraline.

Traces of tramadol in water impact behaviour in a native European fish.

Tramadol is a widely used analgesic with additional antidepressant and anxiolytic effects. This compound has been reported in continental waters reaching concentrations of µg/L as a consequence of its inefficient removal in sewage treatment plants and increasing use over time. In this study, European chubs (Squalius cephalus) were exposed to 1 µg/L of tramadol in water for 42 days with a subsequent 14 days of depuration. Our results revealed that chubs exposed to this analgesic underwent changes in their behaviour as compared to the control group. The behavioural outcome was also influenced by the individual concentration of tramadol in brain tissue. In particular, experimental fish presented anxiolytic-like effects, characterized by less bold and less social individuals. Exposed animals were less frequently out of the shelter and moved a shorter distance, indicating that they explored the new environment less during the boldness test. In the novel object recognition experiment, although they distinguished the new item, they examined it less and displayed a reduced activity. Shoal cohesion was disrupted as observed in an increased distance between individuals. After the depuration phase, this alteration remained whereas the boldness effect disappeared. Moreover, the degree of behavioural changes was correlated with the concentration of the substance in brain. According to our findings, chronic presence of tramadol in the environment can impact the fitness of exposed aquatic fauna by altering evolutionary crucial behaviours.

Applicability of the OECD 455 in-vitro assay for determination of hERa agonistic activity of isoflavonoids.

The Organisation for Economic Co-operation and Development (OECD)-validated transactivation assay using the human estrogen receptor alpha (hERα) Hela9903 cell line is used for activity evaluation of hERα agonists and antagonists. Due to many advantages, this assay is broadly used as an initial screening process. However, response significantly higher from that of 17-ß estradiol (E2) was observed with phytoestrogens for concentrations commonly above 1 µM in previous studies. The main aim of this study was thus to ascertain the applicability of OECD protocol 455 for evaluation of estrogenic activity of natural flavonoids, including known phytoestrogens. The estrogenic activities of aglycones as well as of O-methylated and glycosylated flavonoids were evaluated. Supra-maximal luciferase activity was seen for most of the flavonoids tested at concentrations even below 1 µM. hERα-mediated luciferase expression was confirmed with the competition assay specified in OECD protocol 455. However, at concentrations above 1 µM, non-specific interactions were also observed. Instead of EC50 values, which could not be determined for most of the isoflavonoids tested, the concentrations corresponding to 10% (PC10) and 50% (PC50) of the maximum activity of the positive control, E2, were used for quantitative determination of estrogenic activities. Appropriate evaluation of the data obtained with the current OECD protocol 455 validated assay represents a valuable tool for initial screening of natural flavonoids for estrogenic activity.

Test-dependent expression of behavioral syndromes: A study of aggressiveness, activity, and stress of chub.

Aggressiveness has been one of the behavioral traits most examined with various standard testing methods. We used two distinct methods (the mirror and the real opponent tests) to evaluate individual aggression and relate it to the activity and individual stress of chub (Squalius cephalus L.). Three hypotheses were formulated and tested: (a) there is a significant positive relationship between the aggressiveness of individuals measured with the mirror and the real opponent tests, indicating their convergent validity; (b) the irregularities in response to the aggressiveness and activity tests lead to the context-specific expression of the behavioral syndromes; and (c) there is a significant positive relationship between the stress induced in individuals by both tests of aggressiveness, demonstrating individually consistent stress-coping strategies. The first and the second hypothesis were confirmed, while the third hypothesis was rejected. Our results suggest that particular tests of aggressiveness could act as a situation with high strength, leaving little variation between individual responses. Thus, we propose that for the proper interpretation of various studies using different tests to study identical behavioral traits, it is important to consider the convergent validity of not only the tested behavioral traits but also the individual stress responses. The chub also showed stress relieve through aggressiveness, suggesting the species as a prospective animal model to the study interaction between the stress and the aggressiveness. A detailed aggression ethogram of chub was provided to facilitate the use of this specie in future studies.

Development of pH-Responsive Biopolymeric Nanocapsule for Antibacterial Essential Oils.

It is generally believed that antibacterial essential oils have the potential to become one of the alternatives in preventing diarrheal diseases of monogastric animals. The disadvantage is their low efficiency per oral due to easy degradation during digestion in the stomach. This study compares the efficacy of chitosan, alginate-chitosan, guar gum-chitosan, xanthan gum-chitosan and pectin-chitosan nanocapsules to the synthesis of pH-responsive biopolymeric nanocapsule for Thymus vulgaris, Rosmarinus officinalis and Syzygium aromaticum essential oils. Using spectrophotometric approach and gas chromatography, release kinetics were determined in pH 3, 5.6 and 7.4. The growth rates of S. aureus and E. coli, as well as minimal inhibition concentration of essential oils were studied. The average encapsulation efficiency was 60%, and the loading efficiency was 70%. The size of the nanocapsules ranged from 100 nm to 500 nm. Results showed that chitosan-guar gum and chitosan-pectin nanocapsules released 30% of essential oils (EOs) at pH 3 and 80% at pH 7.4 during 3 h. Similar release kinetics were confirmed for thymol, eugenol and α-pinene. Minimal inhibition concentrations of Thymus vulgaris and Syzygium aromaticum essential oils ranged from 0.025 to 0.5%. Findings of this study suggest that the suitable pH-responsive nanocapsule for release, low toxicity and antibacterial activity is based on chitosan-guar gum structure.

Altered thermoregulation as a driver of host behaviour in glochidia-parasitised fish.

Parasites alter their host behaviour and vice versa as a result of mutual adaptations in the evolutionary arms race. One of these adaptations involves changes in host thermoregulation, which has the potential to harm the parasite and thereby act as a defence mechanism. We used a model of the brown trout (Salmo trutta) experimentally parasitised with glochidia ectoparasitic larvae from the endangered freshwater pearl mussel (Margaritifera margaritifera) to reveal whether parasitisation alters fish behavioural thermoregulation. A study using radiotelemetry temperature sensors was performed during almost one year of the M. margaritifera parasitic stage. Glochidia-infested S. trutta altered their thermoregulation through active searching for habitats with different thermal regimes. The general preference for temperatures in infested fish varied and was either above or below the temperature preferred by uninfested individuals. Infested fish also preferred different temperatures across localities, whereas uninfested fish maintained their thermal preference no matter which stream they inhabited. Glochidia further induced the expression of a behavioural syndrome among S. trutta personality traits, suggesting that it might increase the probability that the fish host would occur in the glochidia temperature optimum. Our findings present the first evidence that thermoregulation plays a fundamental role in the relationship of affiliated mussels and their fish hosts. Incorporating thermoregulation as a factor in the study of this relationship can help to interpret results from previous behavioural studies, as well as to optimise management measures related to endangered mussels.

Improved river continuity facilitates fishes' abilities to track future environmental changes.

Barriers represent one of the largest anthropogenic impacts on the ecological status of rivers, and they also potentially restrict fishes' ability to respond to future environmental changes. Thus, river management aims to restore the longitudinal connectivity of rivers to allow continuous migration and movement of water, sediments and biota. However, it is often unclear whether the targeted barriers are also those most relevant for fish species, particularly to track future habitat shifts caused by environmental change. In this study, we applied species distribution models and the GIS-based fish dispersal model FIDIMO to evaluate the impacts of barriers (e.g. weirs and dams) on the dispersal of 17 native fish species in the European River Elbe with a particular focus on climate- and land use-induced habitat shifts. Specifically, we compared three scenarios of longitudinal connectivity: (i) current longitudinal connectivity, (ii) connectivity improvements as planned by river managers for 2021 and (iii) a reference with full longitudinal connectivity. The models indicated that barriers restricted the movement of two modeled fish species on average, thus impeding fishes' abilities to track future habitat shifts. Moreover, the number of species affected by barriers increased downstream. For the River Elbe, our results suggest that river management has most likely identified the most relevant barriers in respect to the modeled species and future environmental change. We emphasize that river management and barrier prioritization must thoroughly consider species-specific movement and dispersal abilities, as well as the specific spatial arrangement of barriers in the river system in relation to the spatial distribution of species' populations and suitable habitats.

The future distribution of river fish: The complex interplay of climate and land use changes, species dispersal and movement barriers.

The future distribution of river fishes will be jointly affected by climate and land use changes forcing species to move in space. However, little is known whether fish species will be able to keep pace with predicted climate and land use-driven habitat shifts, in particular in fragmented river networks. In this study, we coupled species distribution models (stepwise boosted regression trees) of 17 fish species with species-specific models of their dispersal (fish dispersal model FIDIMO) in the European River Elbe catchment. We quantified (i) the extent and direction (up- vs. downstream) of predicted habitat shifts under coupled "moderate" and "severe" climate and land use change scenarios for 2050, and (ii) the dispersal abilities of fishes to track predicted habitat shifts while explicitly considering movement barriers (e.g., weirs, dams). Our results revealed median net losses of suitable habitats of 24 and 94 river kilometers per species for the moderate and severe future scenarios, respectively. Predicted habitat gains and losses and the direction of habitat shifts were highly variable among species. Habitat gains were negatively related to fish body size, i.e., suitable habitats were projected to expand for smaller-bodied fishes and to contract for larger-bodied fishes. Moreover, habitats of lowland fish species were predicted to shift downstream, whereas those of headwater species showed upstream shifts. The dispersal model indicated that suitable habitats are likely to shift faster than species might disperse. In particular, smaller-bodied fish (<200 mm) seem most vulnerable and least able to track future environmental change as their habitat shifted most and they are typically weaker dispersers. Furthermore, fishes and particularly larger-bodied species might substantially be restricted by movement barriers to respond to predicted climate and land use changes, while smaller-bodied species are rather restricted by their specific dispersal ability.

Synergistic and antagonistic interactions of future land use and climate change on river fish assemblages.

River ecosystems are threatened by future changes in land use and climatic conditions. However, little is known of the influence of interactions of these two dominant global drivers of change on ecosystems. Does the interaction amplify (synergistic interaction) or buffer (antagonistic interaction) the impacts and does their interaction effect differ in magnitude, direction and spatial extent compared to single independent pressures. In this study, we model the impact of single and interacting effects of land use and climate change on the spatial distribution of 33 fish species in the Elbe River. The varying effects were modeled using step-wise boosted regression trees based on 250 m raster grid cells. Species-specific models were built for both 'moderate' and 'extreme' future land use and climate change scenarios to assess synergistic, additive and antagonistic interaction effects on species losses, species gains and diversity indices and to quantify their spatial distribution within the Elbe River network. Our results revealed species richness is predicted to increase by 0.7-2.9 species by 2050 across the entire river network. Changes in species richness are likely to be spatially variable with significant changes predicted for 56-85% of the river network. Antagonistic interactions would dominate species losses and gains in up to 75% of the river network. In contrast, synergistic and additive effects would occur in only 20% and 16% of the river network, respectively. The magnitude of the interaction was negatively correlated with the magnitudes of the single independent effects of land use and climate change. Evidence is provided to show that future land use and climate change effects are highly interactive resulting in species range shifts that would be spatially variable in size and characteristic. These findings emphasize the importance of adaptive river management and the design of spatially connected conservation areas to compensate for these high species turnovers and range shifts.

Selenium Status of Southern Africa.

Selenium is an essential trace element that exists in inorganic forms (selenite and selenates) and organic forms (selenoamino acids, seleno peptides, and selenoproteins). Selenium is known to aid in the function of the immune system for populations where human immunodeficiency virus (HIV) is endemic, as studies suggest that a lack of selenium is associated with a higher risk of mortality among those with HIV. In a recent study conducted in Zambia, adults had a median plasma selenium concentration of 0.27 µmol/L (IQR 0.14-0.43). Concentrations consistent with deficiency (<0.63 µmol/L) were found in 83% of adults. With these results, it can be clearly seen that selenium levels in Southern Africa should be investigated to ensure the good health of both livestock and humans. The recommended selenium dietary requirement of most domesticated livestock is 0.3 mg Se/kg, and in humans above 19 years, anRDA (recommended daily allowance) of 55 mcg Se/per dayisis recommended, but most of the research findings of Southern African countries have recorded low levels. With research findings showing alarming low levels of selenium in soils, humans, and raw feed materials in Southern Africa, further research will be vital in answering questions on how best to improve the selenium status of Southern African soils and plants for livestock and humans to attain sufficient quantities.

The effect of parasitism on boldness and sheltering behaviour in albino and pigmented European catfish (Silurus glanis).

Parasites can change the behaviour of their hosts, but little attention has been given to the relationship between parasite effects on host behaviour and colouration. The correlation between disrupted melanin production and alterations in various physiological and behavioural traits, e.g., aggression, shoaling behaviour, stress responsiveness and sensitivity to brood parasitism, has been reported in albino fish. We hypothesized that parasitism would affect the behaviour of albino and pigmented conspecifics differently. In laboratory conditions, we infested a group of pigmented and a group of albino individuals of European catfish Silurus glanis with glochidia of two Uninoidea species, namely, the native species Anodonta anatina and the invasive species Sinanodonta woodiana, and investigated the effect of parasitization on the boldness and sheltering behaviour of the hosts. The behaviour of albino individuals differed from that of pigmented conspecifics both before and after parasitization. Parasitization with glochidia did not affect sheltering behaviour, but it increased boldness in pigmented individuals, whereas albino individuals did not exhibit any changes in behaviour. Sheltering results were consistent in both binomial and continuous variable analyses, whereas boldness was significant only in the binomial analyses. Our results demonstrate the reduced susceptibility of the albino phenotype to glochidia infestation, together with questions of the choice of analyses.

Differential effects of antidepressant sertraline in glochidia-fish interactions involving drug transfer from parasite to host.

This study examined the impact of sertraline, an antidepressant common in treated wastewater, on the host-parasite dynamics between parasitic freshwater mussel (Unio tumidus, Unionidae) larvae (glochidia) and their host fish (Squalius cephalus, Cyprinidae). Employing a full-factorial design, both fish and glochidia were subjected to sertraline at the combinations of 0 µg L-1 (control), 0.2 µg L-1 (environmentally relevant concentration), and 4 µg L-1 (elevated concentration, short-term exposure of the parasite). The results showed that long-term host exposure (involving intensive sertraline accumulation in the fish brain) marginally increased subsequent glochidia attachment success by 2 %, while parasite exposure at the same environmentally relevant concentrations had no detectable effect. There was also no effect of exposure of glochidia to 0.2 µg L-1 of sertraline on their viability and encapsulation success during the initial parasitic stage. However, a significant alteration in attachment behavior, marked by a 3.3 % increase in attachment success and changes in the glochidia spatial distribution on the host body, was noted after 24 h of glochidia exposure to 4 µg L-1 of sertraline. Importantly, this study provides the first evidence of sertraline transfer from exposed glochidia to nonexposed host fish, as indicated by elevated levels of sertraline (12.8 ng g-1) in the brain tissue of nonexposed hosts. These findings highlight the subtle yet significant effects of pharmaceutical pollutants on freshwater ecosystems but also underscore the importance of understanding the unexpected dynamics of such contamination to predict and address future ecological changes.

Monitoring of taurine dietary supplementation effect on parameters of Duroc boar ejaculate in summer season.

The aim of this experiment was to find out whether the taurine supplementation in daily ration had an effect on quantity or quality of Duroc boar ejaculate. The experiment duration was from June to August, when it could assumed the possible occurrence of heat stress. For the study was chosen 12 Duroc boars of approximately the same age and condition. The control group of 6 Duroc boars was fed only by basic diet and the experimental group of 6 Duroc boars was fed by the same basic diet with supplementation of 15 g taurine/boar/day. Ejaculate was collected once a week by hand glowed technique. From ejaculate parameters were monitored volume of ejaculate, sperm concentration, total amount of sperm, morphologically abnormal sperm, taurine concentration and GSH/GSSH concentration. From microscopic analysis, results were statistically significant in motility in June and July (P<0.05). In biochemical results, a significant difference (P<0.05) has been found between the experimental groups in the concentrations of taurine as well as GSH/GSSG in ejaculate which indicates the effect of heat stress on boars during the experimental period.

Use of nanotechnology-based nanomaterial as a substitute for antibiotics in monogastric animals.

Nanotechnology has emerged as a promising solution for tackling antibiotic resistance in monogastric animals, providing innovative methods to enhance animal health and well-being. This review explores the novel use of nanotechnology-based nanomaterials as substitutes for antibiotics in monogastric animals. With growing global concerns about antibiotic resistance and the need for sustainable practices in animal husbandry, nanotechnology offers a compelling avenue to address these challenges. The objectives of this review are to find out the potential of nanomaterials in improving animal health while reducing reliance on conventional antibiotics. We examine various forms of nanomaterials and their roles in promoting gut health and also emphasize fresh perspectives brought by integrating nanotechnology into animal healthcare. Additionally, we delve into the mechanisms underlying the antibacterial properties of nanomaterials and their effectiveness in combating microbial resistance. By shedding light on the transformative role of nanotechnology in animal production systems. This review contributes to our understanding of how nanotechnology can provide safer and more sustainable alternatives to antibiotics.

Mycotoxin production in different varieties of Dactylis glomerata L. silage in response to biological and chemical additives.

Silage has been identified as a source of different microbial toxins, that may impair farm animal health and productivity as human health can also be compromised. In this sense, the aim of this study was to determine the impact of silage additives on the concentrations of deoxynivalenol (DON) and zearalenone (ZEN) mycotoxins and, eventually, to evaluate the hygienic quality of orchardgrass (Dactylis glomerata L.) silage based on the concentration of them compared to control silage. This study evaluated the influence of biological and chemical additives used in six different varieties of orchardgrass silage on DON and ZEN mycotoxin contents for the first time. The content of both fusariotoxins (DON and ZEN) in fresh matter and grass silage were below the threshold stipulated by the European Commission. The concentration of DON ranges from ~21.86 to 37.26 ng/kg, ~10.21 to 15 ng/kg, ~20.72 to 29.14 ng/kg; and ZEN range from ~3.42 to 7.87 ng/kg, ~3.85 to 8.62 ng/kg and ~2.15 to 5.08 ng/kg, in control, biological and chemical silages, respectively. In general, the biological additive was more efficient for preventing DON contamination, whereas the chemical additive was more efficient for preventing ZEN contamination in grass silage. In summary, the results obtained in this work demonstrate that biological and chemical additives can inhibit fungal growth and mycotoxin production on Dactylis glomerata L. silage and whose use could prevent animal and human diseases.

Aggression repeatability in stressed fish in response to an environmental concentration of sertraline and lunar cycle as evidenced by brain metabolomics.

Sertraline is an environmental pollutant which received magnified scientific attention due to its global presence in waters. Adverse effects on feeding, reproduction and other traits were observed mostly in unstressed aquatic organisms. Chronic stress, however, induces significant physiological changes, and the effects of sertraline in stressed fish may differ from those observed in non-stressed individuals. The current laboratory study addresses this gap by repeatedly monitoring the individual aggression of chronically stressed juvenile chub (Squalius cephalus L.) using the non-reversing mirror test at an environmental sertraline concentration of 0.022 g/L every three to four days for a period of 39 days. Specifically, it was hypothesized that the level and repeatability of aggressiveness would be (i) correlated with the concentration of sertraline/norsertraline in the fish brain; (ii) linked to the individual brain metabolomic profile described by LC-HRMS analyses; (iii) related to the lunar cycle. Sertraline led to an increase in fish aggression and more repeatable/consistent behaviour compared to control fish. While the level of sertraline in the brain did not correlate with aggressiveness, aggressive responses increased with higher norsertraline concentration. The observed aggressive behaviour also varied depending on the individual metabolomic profile of the brain. The behavioural outcome and metabolic change in fish brain may indicate that sertraline has demonstrated neuroprotective effects by reducing cortisol release. It is possible that fish exposed to sertraline could suffer a blunted stress response under the chronic stressors in the wild. Aggressiveness of both treatments evolved in time, revealing a sinusoid-like pattern corresponding to a lunar cycle with a peak of the aggressiveness during the new moon. There is a need for future studies to focus on this relationship to reveal its details and general validity. Our results emphasize that long-term behavioural variability should generally be taken into account in laboratory behavioural studies.