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Within aquatic ecosystems, chemosensory cues are widely used as publicly available risk assessment information, allowing prey to optimize behavioural decisions. In sexually dimorphic species, males and females often have different responses to local predation threats. According to the ‘distracted male’ hypothesis, reproductively active males should show a reduced response to risk cues compared to conspecific females due to the potentially high costs of lost courtship and mating opportunities among males. Recent evidence supports this hypothesis, showing that adult male guppies (Poecilia reticulata) show a reduced or absent response to chemosensory risk cues. Here, we further test the ‘distracted male’ hypothesis by testing non-reproductive male and female guppies, collected from the Lopinot River (high predation) or the Upper Aripo River (low predation). We found that juvenile male and female guppies exhibited similar response patterns. Consistent with our predictions, both juvenile male and female guppies collected from a high predation site exhibited a similar antipredator response (reduced number of lines crossed) when exposed to conspecific alarm cues or a novel odour (vs. water control). Those collected from a low predation site showed similar responses to conspecific alarm cues and no response to a novel odour or the water control. Combined, our results suggest that unlike adult guppies, non-reproductive male and female guppies make similar behavioural decisions in response to acute predation cues. As predicted by the ‘distracted male’ hypothesis, the previously reported absence of a response to chemosensory risk assessment cues among adult males may be due to a devaluation of risk assessment information in favour of continued mating. [ABSTRACT FROM AUTHOR]

Social learning, where animals learn from other individuals, occurs in many diverse species. The influential but debated 'costly information' hypothesis posits that animals will rely more on social information in high-risk contexts, such as under increased predation risk. We examined and compared the effects of perceived predation risk on social learning of foraging sites in female Trinidadian guppies from wild and domestic populations raised in common-garden environments. We used a demonstrator-observer pairing where a subject could observe conspecific 'demonstrators' feeding from one of two feeders, and measured whether the observer subsequently spent more time at a demonstrated or non-demonstrated feeder. We manipulated perceived predation risk using alarm cue (conspecific skin extract). Stress responses and social learning differed between the two populations. Most notably, high predation risk enhanced social learning in the wild-type guppies, but depressed it in the domestic guppies. Thus, fish from both populations were able to socially learn, but under opposing contexts. These results suggest social learning propensities are the product of multiple interacting systems, and biases to favour social learning can emerge dependent on evolutionary history and current conditions. [ABSTRACT FROM AUTHOR]

Evolution of male-biased coloration in the guppy Poecilia reticulata is driven by sexual and natural selection. The colorful male ornaments are attractive to females, but also attract predators. Distinct predation regimes in Trinidadian streams promote the evolution of different guppy color morphs, with male ornamentation and female mate preference also co-evolving among populations. How attractive a male guppy color morph is to a female depends not only on the coloration itself, but also on how strongly the morph evokes stimulation of the female visual system. Both allele type and gene expression levels of cone opsin genes play a role in female mate preferences. Previous studies have demonstrated that predation can alter female guppy mate choice, but the underlying mechanism remains unclear. Here, I hypothesize that guppies adjust their cone opsin expression profiles in response to predation pressure. Although I detected a significant change in LWS-R transcription in response to predation, cone opsin expression profiles in adult female guppies do not appear to be driven by predation pressure. However, the impacts of predation pressure on developmental plasticity in cone opsin expression and brain anatomy remain promising avenues of further investigation to determine how predators affect female mate preference in guppies. [ABSTRACT FROM AUTHOR]

Animal personalities are differences in behaviour among individuals of the same species that are consistent over time and contexts. The integration of animal personality into conservation actions is hampered by limited understanding of personality traits in non‐model organisms. We estimated repeatabilities and correlations between behaviours in Nannoperca vittata (western pygmy perch), a threatened freshwater fish species endemic to south‐western Australia, and, for comparative purposes, in Poecilia reticulata (guppy), a species frequently used in personality research. Each fish was measured four times for each of seven behavioural variables, presumed to reflect five underlying personality traits. Track length (TL) was used as a measure of activity; time spent in a risky zone (RZ) and time to emergence (ET) for boldness; latency to approach a novel object (LA) and time spent close to the object (TS) for exploration; time spent close to a mirror (CV) for sociability and number of attacks at the mirror (AT) for aggression. Four behavioural variables (TL, RZ, ET and CV) were significantly repeatable in N. vittata and also in P. reticulata. There was a lack of concordance in phenotypic and among‐individual correlations between variables in both species, emphasising the importance of partitioning trait covariances to infer behavioural syndromes. Significant among‐individual correlations were found between activity, boldness and sociability variables in N. vittata, consistent with a proactive‐reactive personality axis, but not in P. reticulata. Personality variation should be considered in conservation actions for N. vittata, particularly with respect to unintended consequences of domestication selection in captive breeding and release. [ABSTRACT FROM AUTHOR]

Consumers vary in their excretion of nitrogen and phosphorus, altering nutrient cycles and ecosystem function. Traditional mass balance models that focus on dietary and tissue nutrients have poorly explained such variation in excretion. Here, we contrast diet and tissue nutrient models for nutrient excretion with predation risk, an often overlooked factor, using the Trinidadian guppy (Poecilia reticulata) as our model system. We surveyed guppies at 12 sites spread across two streams with parallel gradients in food quality and predation risk. At each site, we assessed guppy diet, tissue nitrogen (N), and phosphorus (P) content, and N and P excretion. Predation risk best explained guppy excretion, especially P: guppies excreted less in sites with a dominant predator, while traditional models for excretion rate based on diet quality and tissue nutrients failed to explain it. Guppy tissue N (but not P) most closely correlated with guppy diet quality, showing evidence for flexible homeostasis. Our work extends previous laboratory studies' results to natural streams and shows that predation risk alters feeding behavior and physiology, driving substantial variation in guppy nutrient, particularly P, excretion rates. We suggest that predation risk is an important factor determining nutrient excretion variation, warranting further attention. Our results also show that tissue nutrients and excretion nutrients are decoupled. [ABSTRACT FROM AUTHOR]

In the present study, a mathematical model was developed to evaluate fish demography under different temperature conditions. The target organism was Poecilia reticulata whose population reared under controlled conditions was subjected to different temperatures (24, 28 and 30 °C) in order to understand how this affects the organisms. Individual fish lengths were recorded before and after the experiment, as well as data related to birth and mortality before, during and after the acclimatization period. From the life cycle of P. reticulata, six differential equations were derived, one for each stage of development, which allowed us to better model population growth as a function of time and environmental variables, in this case, water temperature. Subsequently, the stationary points of these equations were calculated, which allowed a stability analysis of the system to be carried out. In addition, a population projection was made using the data obtained from the proposed model, which allowed to better understand how different temperatures affect the size and dynamics of the P. reticulata population. Significant differences were found in Dunn's test for fish length among the different temperature treatments, suggesting a direct relationship between water temperature and the growth of these organisms. This study provides valuable information on how environmental conditions can influence the population dynamics of P. reticulata. [ABSTRACT FROM AUTHOR]

Non‐native species represent a significant threat to biodiversity, particularly in aquatic environments where they are often introduced for purposes such as fishing or the aquarium trade. This study aimed to evaluate the influence of isolation and the size of federal protected areas (PAs) on the number of non‐native and native freshwater fish species in Brazilian PAs. Data from Brazilian PAs were gathered, including year of creation, buffer of human impacts around the PA, PA categories, coverage by freshwater, tourist visits, sampling sites, geographical coordinates (predictor variables) and information on the number of non‐native and native freshwater fish species (response variables). Linear regression analysis was employed to examine the influence of predictor variables on the number of non‐native and native fish species. A total of 33 different non‐native fish species were identified, with Poecilia reticulata, Hyphessobrycon eques, Hoplias lacerda and Cichla kelberi being the most widespread, occurring in 15, 7, 5 and 4 distinct PAs, respectively. The overall fish biodiversity within PAs encompassed 2670 species, with the National Park of Anavilhanas and the Environmental Protection Area of Ilha e Várzea do Paraná exhibiting the highest species richness. Greater human impact, larger coverage by freshwater and increased sampling effort were positively correlated with the number of recorded non‐native species. Factors such as year of creation, type of PA and tourist visitation did not have a significant effect. In contrast, native species exhibited a higher number of occurrences in PAs with lower human impact, longer histories, larger freshwater coverage areas and more extensive sampling efforts. These findings underscore the necessity for comprehensive management strategies to mitigate the impact of non‐native species on biodiversity within PAs. [ABSTRACT FROM AUTHOR]

Studies of both professional science practice and children's science learning show that care is not merely ancillary to disciplinary work but a core and generative constituent of science practice. In science education research, however, students' care is often overlooked. In this paper, we describe the expression of care across two STEM classrooms (6th and 9th grade) studying biology and ecology and participating in a pen pal exchange. We analyze artifacts from the pen pal exchange as well as students' retrospective interviews and written reflections. Two ways of expressing care surfaced in students' letters: caring for guppies and caring for pen pals. We describe each form of care using examples from our data. We find that students' care for guppies and pen pals was both instrumental (in service of their investigations) and intrinsic (positioning guppies and pen pals as inherently valuable). We then connect these findings to studies of care in children's science learning and in professional science. We discuss methodological and practical implications for recognizing and analyzing how students' care manifests in classrooms and for designing learning activities that cultivate care. [ABSTRACT FROM AUTHOR]

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Symbionts tend to be aggregated on their hosts, such that few hosts harbor the majority of symbionts. This ubiquitous pattern can result from stochastic processes, but aggregation patterns may also depend on the type of host–symbiont interaction, along with traits that affect host exposure and susceptibility to symbionts. Untangling how aggregation patterns both within and among populations depend on stochastic processes, interaction type and host traits remains an outstanding challenge. Here, we address this challenge by using null models to compare aggregation patterns in a neutral system of Balanomorpha barnacles attached to patellid limpets and a host–parasite system of Gyrodactylus spp. monogeneans and their Trinidadian guppy Poecilia reticulata hosts. We first used a model to predict patterns of symbiont–host aggregation due to random partitioning of symbionts to hosts. This null model accurately predicted the aggregation of barnacles on limpets, but the degree of aggregation varied across 303 quadrats. Quadrats with larger limpets had less aggregated barnacles, whereas aggregation increased with variation in limpet size. Across 84 guppy populations, Gyrodactylus spp. parasites were significantly less aggregated than predicted by the null model. As in the neutral limpet–barnacle system, aggregation decreased with mean host size. Parasites were significantly less aggregated on males than females because male guppies tended to have higher prevalence and lower parasite burdens than predicted by the null model. Together, these results suggest stochastic processes can explain aggregation patterns in neutral but not parasitic systems, though in both systems host traits affect aggregation patterns. Because the distribution of symbionts on hosts can affect symbiont evolution via intraspecific interactions, and host behavior and evolution via host–symbiont interactions, identifying the drivers of aggregation enriches our understanding of host–symbiont interactions. [ABSTRACT FROM AUTHOR]

Inbreeding impairs the cognitive abilities of humans, but its impact on cognition in other animals is poorly studied. For example, environmental stress (e.g. food limitation and extreme temperatures) often amplifies inbreeding depression in morphological traits, but whether cognition is similarly affected is unclear. We, therefore, tested if a higher temperature (30°C versus 26°C) during development exacerbates any difference in inhibitory control between inbred (f = 0.25) and outbred guppies (Poecilia reticulata). Inhibitory control is an aspect of cognition that is often measured in vertebrates using a detour test, in which animals have to navigate around a transparent barrier to reach a reward. We also tested if inbreeding and temperature affect 'boldness', which is a putative personality trait in guppies. Inbreeding lowered inhibitory control of guppies raised at the higher temperature but not those raised at the control temperature. Inbred fish were significantly less bold than outbred fish. In addition, males, but not females, raised at the higher temperature had significantly lower inhibitory control. There was no effect of temperature on the boldness of either sex. Our study is among the first to test if experimentally induced inbreeding impairs cognition in a non-domesticated vertebrate. We show that both inbreeding and higher temperatures during development can affect the behaviour and cognitive abilities of fish. These findings are noteworthy given the twin threats of rising global temperatures and more frequent inbreeding as habitat fragmentation reduces population sizes. [ABSTRACT FROM AUTHOR]

Simple Summary: Organic insecticides against Aedes aegypti L. mosquitoes are regarded as one of the most important tools for containing arboviruses transmitted by this species, such as dengue, Zika, and chikungunya in tropical countries including Thailand, considering the development of mosquito resistance to synthetic chemical larvicides. The most critical way to contain outbreaks is to control the vector that transmits pathogens. Monoterpenes are new, effective, and eco-friendly alternatives. This study investigated the larvicidal and pupicidal activities of two monoterpenes—geranial and trans-cinnamaldehyde—and their combinations. The efficacies of each formulation were compared against each other and temephos. Binary mixtures were significantly more effective than single formulations or temephos. They are safe for the non-target aquatic predator, guppies (Poecilia reticulata). These combinations make excellent insecticides for both larvae and pupae mosquito vector control, and the results open up the opportunity for both compounds to be developed into eco-friendly products. Monoterpenes are effective and eco-friendly alternatives to conventional chemical larvicides. We tested single and binary mixtures of monoterpenes—geranial and trans-cinnamaldehyde—for their larvicidal and pupicidal activities against Aedes aegypti L. and for non-target toxicity on guppies (Poecilia reticulata Peters), using 1% (w/w) temephos as a reference. Geranial and trans-cinnamaldehyde at 250 ppm showed stronger larvicidal and pupicidal activities with a 100% mortality rate and an LT50 ranging from 0.3 to 0.6 h. All combinations were strongly synergistic against larvae and pupae compared to single formulations, with an increased mortality value (IMV) of 6% to 93%. The combination of geranial + trans-cinnamaldehyde (1:1) at 200 ppm showed the highest impact, with an IMV of 93%. The strongest larvicidal and pupicidal activities, a 100% mortality rate, and an LT50 of 0.2 h were achieved by geranial + trans-cinnamaldehyde (1:1) 500 ppm. They were thirty times more effective than a 1% temephos solution (LT50 ranging from 6.7 to 96 h) and caused obviously shriveled cuticles and a swollen respiratory system. All single and binary mixtures were not toxic to the guppies. Thus, the combination of geranial + trans-cinnamaldehyde has great potential as a safe insecticide for controlling mosquito larvae and pupae. [ABSTRACT FROM AUTHOR]

It has been argued that a preexisting sensory bias for food color influences female mate preference for male ornament color. However, the effect of diet color over a short period on female preference for color-polymorphic male ornaments has not yet been investigated. In this study, we examined the effect of diet color on female preference for mate color in the guppy Poecilia reticulata, with color-polymorphic ornaments such as orange and black spots. From an early age, females were reared on a diet with orange and black color, respectively. A dichotomous mate choice experiment using females was conducted between males with large orange spots and males with large black spots. Females fed on an orange-colored diet preferred males with large orange spots, whereas those fed on a black-colored diet preferred males with large black spots. Afterward, the diet color treatment for the females was reversed for seven days. This dietary color alteration resulted in the reversal of female preference for male color. These results suggest that diet color has a great influence on female preference for mate color, even within a short period, and environmental gradients may function to maintain color-polymorphic male ornaments in this species. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) negatively impacts organisms in many ways, from their feeding behaviors to their response and ability to deal with disease. Our knowledge of ALAN is focused on hosts, but we must also consider their parasites, which constitute half of all described animal species. Here, we assessed the impact of light exposure on a model host–parasite system (Poecilia reticulata and the ectoparasitic monogenean Gyrodactylus turnbulli). First, parasite‐free fish were exposed to 12:12 h light:dark (control) or 24:0 h light:dark (ALAN) for 21 days followed by experimental infection. Second, naturally acquired G. turnbulli infections were monitored for 28 days during exposure of their hosts to a specified light regime (6:18 h, 12:12 h, or 24:0 h light:dark). Experimentally infected fish exposed to constant light had, on average, a greater maximum parasite burden than controls, but no other measured parasite metrics were impacted. Host feeding behavior was also significantly affected: fish under ALAN fed faster and took more bites than controls, whilst fish exposed to reduced light fed slower. Thus, ALAN can impact parasite burdens, even in the short term, and altering light conditions will impact fish feeding behavior. Such responses could initiate disease outbreaks or perturb food‐webs with wider ecological impacts. [ABSTRACT FROM AUTHOR]

Fish coloration and growth can be enhanced by supplementing Spirulina in feed, though it is relatively expensive. As a cost-effective alternative, Chlorella was used in this study to replace Spirulina. The experiment was conducted by feeding one-day-old guppy (Poecilia reticulata) fry with either a control feed without algal supplementation (C), a diet supplemented with 5% Spirulina (5SP), or a diet supplemented with 5% Chlorella (5CH). After 30 days, the fry fed 5CH had significantly poorer growth performance (p<0.05) compared to 5SP, but not different from the control. Interestingly, there was a trend toward improved final weight and specific growth rate in the 5CH group, though the differences were not statistically significant compared to both 5SP and the control. Similar trends were observed for fry production per female. Additionally, no significant differences were found among treatments in terms of survival (ranged 96-97%), stress tolerance, and most reproductive traits (such as fry size). The colour intensity of fish fed both the 5SP and 5CH diets was significantly enhanced (p<0.05) compared to the control group. In conclusion, supplementing guppy feed with 5% Chlorella can replace Spirulina at the same rate for improving colour intensity, without negative effects on growth, survival, stress, or reproductive performances. However, further studies using higher inclusion levels of Chlorella are recommended, given the slight trend toward improved final weight and fry production in fish fed the Chlorella-supplemented diets. [ABSTRACT FROM AUTHOR]

Research Highlight: Aich, U., Polverino, G., Yazdan Parast, F., Melo, G. C., Tan, H., Howells, J., Nosrati, R., & Wong, B. B. M. (2024). Long‐term effects of widespread pharmaceutical pollution on trade‐offs between behavioural, life history and reproductive traits in fish. Journal of Animal Ecology. https://doi.org/10.1111/1365‐2656.14152. Pharmaceutical pollutants are increasingly common in aquatic ecosystems, and organisms living there are the unintended targets of these compounds, originally designed for humans. However, our understanding of these effects remains limited. In a recent study, Aich et al. (2024) investigated the effects of fluoxetine on a small freshwater fish, the guppy (Poecilia reticulata), with particular emphasis on behaviour. The authors found that, after multigenerational exposure to ecologically relevant concentrations of this compound, there was minimal impact on average behavioural traits at the population level. However, fluoxetine exposure reduced within‐individual behavioural plasticity and altered the delicate equilibrium among these traits. These findings could have far‐reaching evolutionary implications for how individuals and populations may respond to environmental changes and highlight the need for behavioural ecotoxicology to move beyond population‐level effects. This research provides valuable insights into the subtle and multifaceted—yet profound—impacts of pollutants on ecological and evolutionary processes, highlighting the importance of studying behavioural responses at the individual level to predict how populations will respond to our rapidly changing world. [ABSTRACT FROM AUTHOR]

In our rapidly changing world, understanding how species respond to shifting conditions is of paramount importance. Pharmaceutical pollutants are widespread in aquatic ecosystems globally, yet their impacts on animal behaviour, life‐history and reproductive allocation remain poorly understood, especially in the context of intraspecific variation in ecologically important traits that facilitate species' adaptive capacities. We test whether a widespread pharmaceutical pollutant, fluoxetine (Prozac), disrupts the trade‐off between individual‐level (co)variation in behavioural, life‐history and reproductive traits of freshwater fish. We exposed the progeny of wild‐caught guppies (Poecilia reticulata) to three field‐relevant levels of fluoxetine (mean measured concentrations: 0, 31.5 and 316 ng/L) for 5 years, across multiple generations. We used 12 independent laboratory populations and repeatedly quantified activity and risk‐taking behaviour of male guppies, capturing both mean behaviours and variation within and between individuals across exposure treatments. We also measured key life‐history traits (body condition, coloration and gonopodium size) and assessed post‐copulatory sperm traits (sperm vitality, number and velocity) that are known to be under strong sexual selection in polyandrous species. Intraspecific (co)variation of these traits was analysed using a comprehensive, multivariate statistical approach. Fluoxetine had a dose‐specific (mean) effect on the life‐history and sperm trait of guppies: low pollutant exposure altered male body condition and increased gonopodium size, but reduced sperm velocity. At the individual level, fluoxetine reduced the behavioural plasticity of guppies by eroding their within‐individual variation in both activity and risk‐taking behaviour. Fluoxetine also altered between‐individual correlations in pace‐of‐life syndrome traits: it triggered the emergence of correlations between behavioural and life‐history traits (e.g. activity and body condition) and between life‐history and sperm traits (e.g. gonopodium size and sperm vitality), but collapsed other between‐individual correlations (e.g. activity and gonopodium size). Our results reveal that chronic exposure to global pollutants can affect phenotypic traits at both population and individual levels, and even alter individual‐level correlations among such traits in a dose‐specific manner. We discuss the need to integrate individual‐level analyses and test behaviour in association with life‐history and reproductive traits to fully understand how animals respond to human‐induced environmental change. [ABSTRACT FROM AUTHOR]

Fish are excellent bioindicators and can reveal the presence of plastic in the environment. Diagnosing the composition and abundance of polymers in the fish diet makes it possible to evaluate their point sources and possible trophic transfers. We aimed to use the gastrointestinal contents of Poecilia reticulata in subtropical urban streams to detect the occurrence, shape, color, size, and chemical composition of polymers. For this, the diet of 240 individuals was analyzed using the volumetric method, and the microplastics (MPs; < 5 mm) recorded were characterized using Raman spectroscopy. Individuals predominantly consumed organic detritus and aquatic macroinvertebrates, with higher proportions of Diptera. A total of 111 plastic particles (< 0.5 to 12 mm) were recorded, and a subset of 14.4% was subjected to a micro-Raman spectrometer (830 nm excitation). The occurrence of polyethylene terephthalate (PET) and polypropylene (PP) with phthalocyanine dye was recorded. Some fragments could not be identified by Raman, but they contained indigo blue dye. Poecilia reticulata had a predominantly detritivorous diet with a record of plastic consumption, reflecting environmental pollution. Our results demonstrate that individuals of P. reticulata have ingested MPs in urban streams. This reinforces the need for future studies on the relationship between the presence of MPs in fish and the level of pollution in streams, comparisons with species of different feeding habits, and the potentially harmful effects on the entire biota. [ABSTRACT FROM AUTHOR]

With the growth of the fashion and textile industries into the twenty-first century, associated pollution has become pervasive. Fibre-based microplastics are the most common types of plastics recovered from aquatic ecosystems encouraging the move towards organic fibre usage. Often marketed as biodegradable and 'environmentally friendly', organic textile fibres are seen as less harmful, but their impacts are understudied. Here, we assess the health effects of reconstituted bamboo-viscose fibres, processed bamboo-elastane fibres (both at 700 fibres/L) and their associated dye (Reactive Black-5, at 1 mg/L) on fish, with an emphasis on disease resistance utilising an established host-parasite system: the freshwater guppy host (Poecilia reticulata) and Gyrodactylus turnbulli (monogenean ectoparasite). Following 3 weeks exposure to the bamboo fibres and associated dye, half the experimental fish were infected with G. turnbulli, after which individual parasite trajectories were monitored for a further 17 days. Overall, exposures to reconstituted bamboo-viscose fibres, processed bamboo-elastane fibres or dye were not associated with any change in host mortality nor any significant changes in parasite infection burdens. When analysing the routine metabolic rate (RMR) of fish, uninfected fish had, on average, significantly impacted RMR when exposed to processed bamboo-elastane (increased RMR) and reconstituted bamboo-viscose (decreased RMR). Hosts exposed to reconstituted bamboo-viscose and the associated dye treatment showed significant changes in RMR pre- and post-infection. This study bolsters the growing and needed assessment of the potential environmental impacts of alternative non-plastic fibres; nevertheless, more research is needed in this field to prevent potential greenwashing. [ABSTRACT FROM AUTHOR]

Behavioural traits are key to promote invasion success because they are easier to adjust to changing environmental conditions than morphological or life history traits. Often, research has overlooked variance in behavioural traits within populations or has assumed it to be mere noise. However, a recent focus towards individual variation of behaviour of successful invaders has revealed new and more profound insights into the invasion process. Behavioural variation within a population could lead to more successful invasions, as they include individuals with diverse behaviours, which ensures at least some individuals could be able to cope with changing conditions. The aim of this research was to examine if invasive guppies (Poecilia reticulata) present within‐population differences in their sociability (time spent associating with a shoal) when interacting with conspecifics or heterospecifics. Guppies presented significant differences in their individual tendencies to associate with conspecific or heterospecific shoals. There were among‐individual differences in the time spent shoaling with conspecifics versus heterospecifics, where most individuals did not differ in their sociability with conspecifics or heterospecifics, and only 22% of individuals presented a higher tendency to associate with conspecifics. Our results are the first to show individual differences in fish' tendencies to associate with heterospecifics among individuals of the same population and rearing conditions. Given that associations with heterospecific natives have been found to be as beneficial as associations with conspecifics for invaders, our results contribute to the understanding of mechanisms behind heterospecific sociability between natives and invaders. [ABSTRACT FROM AUTHOR]

Parental effects, or parental phenotypes affecting offspring phenotypes, are widespread across taxa, yet there is significant variation within species regarding which offspring traits are affected. One reason for this observed variation could be the type of sensory cues present in the parental environment. By exposing parents to sensory cues containing different information about the same ecological stressor, we can determine whether information is integrated differently by parents based on cue type, leading to differential trait development in offspring. In this study, we utilized predator cues, which can be found in isolation and in combination in natural settings, to test whether cue type plays a role in differential phenotype expression in Trinidadian guppies, Poecilia reticulata. Parents were exposed to predator cues (visual, olfactory or both combined) over 14 days, after which we assessed life history traits, morphology and activity. Offspring were then raised with no predator cues and tested for morphology and activity in adulthood. No differences in life history traits were observed across 10 weeks. In line with previous findings, behaviour differed in both the parent and F1 generations in response to predator cues; however, effects were dependent on cue type and sex. Our results suggest that exposure to even a single sensory cue is strong enough to initiate a cascade of responses both in parent and F1 generations, and that interacting factors such as cue type and sex lend importance to understanding consequences of parent risk perception for offspring. • Guppy adults were exposed to olfactory, visual or combined predator cues. • Offspring of adults exposed to different sensory cues were raised in freshwater. • Adults differed in behaviour but not life history based on sex and sensory cue type. • Offspring differed in morphology and behaviour based on sex and parental cue type. • Impact of sensory cues across generations may be linked to overall behavioural type. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, environmental DNA technology, 16S rRNA gene sequencing, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were employed to investigate the relationships between Tetrahymena pyriformis, bacteria, and guppies under varying temperature and pH conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observations were studied. Results of this study showed that several bacteria were related to T. pyriformis, and environmental factors affected the interaction between bacteria and T. pyriformis. In the aquaculture system of ornamental fish, the interaction between bacterial microbiota and ciliate protozoa can prevent or promote disease outbreaks, and different physicochemical conditions will affect the relationships between them. We investigated the interaction between bacterial microbiota and the parasite Tetrahymena pyriformis when infecting Poecilia reticulata (guppy) under different physicochemical conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observation were studied or monitored using environmental DNA (eDNA) extraction technology, the qPCR method, and 16s rRNA sequencing, respectively. The morphological identification and phylogenetic analysis of T. pyriformis were carried out. The infected guppy tissue was also stained by the hematoxylin and eosin methods. The results showed: (1) the bacterial communities of water samples were mainly composed of species assigned to Proteobacteria and Bacteroidetes, and Tabrizicola and Puniceicoccaceae were positively correlated with fish mortality, T. pyriformis abundance, and temperature. (2) Arcicella and Methyloversatilis universalis with different correlations between ciliates appeared in different treatment groups, the result of which proved that environmental factors affected the interaction between bacteria and T. pyriformis. (3) Lower temperatures and a higher pH were more beneficial for preventing disease outbreaks. [ABSTRACT FROM AUTHOR]

Several factors influence whether an organism remains in its local habitat. Parasites can, for example, influence host movement by impacting their behavior, physiology, and morphology. In rivers, fish that swim efficiently against the current are able to maintain their position without being displaced downstream, a behavior referred to as positive rheotaxis. We hypothesized that both the presence and number of ectoparasites on a host would affect the ability of fish to avoid downstream displacement and thus prevent them from remaining in their habitat. We used the guppy‐Gyrodactylus host‐ectoparasite model to test whether parasite presence and parasite load had an effect on fish rheotaxis. We quantified rheotaxis of sham‐infected and parasite‐infected fish in a circular flow tank in the laboratory prior to infection and 5–6 days postinfection. Both parasite‐infected and sham‐infected individuals expressed similar levels of positive rheotaxis prior to infection and after infection. However, with increasing parasite numbers, guppies covered less distance in the upstream direction and spent more time in slower flow zones. These results suggest that higher numbers of Gyrodactylus ectoparasites negatively influence rheotactic movements. Further research is needed to understand the ecological and evolutionary implications of this ectoparasite on fish movement. [ABSTRACT FROM AUTHOR]

Males often strategically adjust the number of available sperm based on the social context (i.e. sperm priming response), but it remains unclear how environmental and genetic factors shape this adjustment. In freshwater ecosystems, high ambient temperatures often lead to isolated pools of hotter water in which inbreeding occurs. Higher water temperatures and inbreeding can impair fish development, potentially disrupting sperm production. We used guppies (Poecilia reticulata) to investigate how developmental temperature (26 °C, 30 °C) and male inbreeding status (inbred, outbred) influence their sperm priming response. We also tested if sperm priming was affected by whether the female was a relative (sister) and whether she was inbred or outbred. There was no effect of rearing temperature; male inbreeding status alone determined the number of available sperm in response to female presence, her inbreeding status, and her relatedness. Inbred males produced significantly more sperm in the presence of an unrelated, outbred female than when no female was present. Conversely, outbred males did not alter the number of sperm available in response to female presence or relatedness. Moreover, inbred males produced marginally more sperm when exposed to an unrelated female that was outbred rather than inbred, but there was no difference when exposed to an inbred female that was unrelated versus related. Together, a sperm priming response was only observed in inbred males when exposed to an outbred female. Outbred females in our study were larger than inbred females, suggesting that inbred males strategically allocated ejaculate resources toward females in better condition. [ABSTRACT FROM AUTHOR]

Collective motion is common across all animal taxa, from swarming insects to schools of fish. The collective motion requires intricate behavioral integration among individuals, yet little is known about how evolutionary changes in brain morphology influence the ability for individuals to coordinate behavior in groups. In this study, we utilized guppies that were selectively bred for relative telencephalon size, an aspect of brain morphology that is normally associated with advanced cognitive functions, to examine its role in collective motion using an open-field assay. We analyzed high-resolution tracking data of same-sex shoals consisting of 8 individuals to assess different aspects of collective motion, such as alignment, attraction to nearby shoal members, and swimming speed. Our findings indicate that variation in collective motion in guppy shoals might not be strongly affected by variation in relative telencephalon size. Our study suggests that group dynamics in collectively moving animals are likely not driven by advanced cognitive functions but rather by fundamental cognitive processes stemming from relatively simple rules among neighboring individuals. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is critical for organismal performance and can evolve in response to natural selection. Brain morphology is often developmentally plastic, affecting animal performance in a variety of contexts. However, the degree to which the plasticity of brain morphology evolves has rarely been explored. Here, we use Trinidadian guppies (Poecilia reticulata), which are known for their repeated adaptation to high-predation (HP) and low-predation (LP) environments, to examine the evolution and plasticity of brain morphology. We exposed second-generation offspring of individuals from HP and LP sites to 2 different treatments: predation cues and conspecific social environment. Results show that LP guppies had greater plasticity in brain morphology compared to their ancestral HP population, suggesting that plasticity can evolve in response to environmentally divergent habitats. We also show sexual dimorphism in the plasticity of brain morphology, highlighting the importance of considering sex-specific variation in adaptive diversification. Overall, these results may suggest the evolution of brain morphology plasticity as an important mechanism that allows for ecological diversification and adaptation to divergent habitats. [ABSTRACT FROM AUTHOR]

Introduction: Variation in eye size is sometimes closely associated with brain morphology. Visual information, detected by the retina, is transferred to the optic tectum to coordinate eye and body movements towards stimuli and thereafter distributed into other brain regions for further processing. The telencephalon is an important visual processing region in many vertebrate species and a highly developed region in visually dependent species. Yet, the existence of a coevolutionary relationship between telencephalon size and eye size remains relatively unknown. Methods: Here, we use male and female guppies artificially selected for small- and large-relative-telencephalon-size to test if artificial selection on telencephalon size results in changes in eye size. In addition, we performed an optomotor test as a proxy for visual acuity. Results: We found no evidence that eye size changes with artificial selection on telencephalon size. Eye size was similar in both absolute and relative terms between the two selection regimes but was larger in females. This is most likely because of the larger body size in females, but it could also reflect their greater need for visual capacity due to sex-specific differences in foraging and mating behaviour. Although the optomotor response was stronger in guppies with a larger telencephalon, we found no evidence for differences in visual acuity between the selection regimes. Conclusion: Our study suggests that eye size and visual perception in guppies do not change rapidly with strong artificial selection on telencephalon size. [ABSTRACT FROM AUTHOR]

Animals often moderate behaviours based on environmental and social cues to enhance their chances of survival and reproductive success. This requires reliable cues that reflect changes in ambient conditions. Environmental pollutants can increase communication costs and distort the accuracy of received information, leading to negative effects on the outcome of behavioural adjustments. Consequently, selection may reduce behavioural plasticity to avoid errors or promote more prudent decision making when certain cues become unreliable. In aquatic ecosystems, water turbidity shows high levels of natural variation, but human activities amplify its magnitude and extent by increasing algae and suspended solids in the water. Here, we investigated how elevated levels of water turbidity affected mating decisions made by female guppies in a laboratory setting. Guppies are a widespread species with a broad tolerance of polluted environments, and females rely heavily on visual cues when making mate choice decisions. We manipulated turbidity by adding suspended solids to water and tested how this affected female preference for males with more orange coloration. We found that females spent more time near males with a greater area of orange coloration in low turbidity water, but that this preference disappeared in both the mid and high turbidity water treatments. Moreover, female preferences were repeatable in low turbidity water and high turbidity water but not in mid turbidity water. Together, our results suggest that water turbidity impairs the ability of females to discern male coloration and affects the consistency of mate preferences. This could have consequences for the evolution of male coloration in turbid waters. • Male guppies have vibrant colour patterns indicating quality. • We investigated how water turbidity affects mating decisions by female guppies. • Females preferred to associate with more colourful males in low turbidity water. • Increased turbidity resulted in no preference for more colourful males. • Female mate preference was not repeatable in mid turbidity water. [ABSTRACT FROM AUTHOR]

Heterospecific sociability could enhance invasion success in social species since social non‐natives usually belong to small founding populations during the early stages of invasion. The twospot livebearer (Pseudoxiphophorus bimaculatus) is native to Central America and southern Mexico and is recently recognised as invasive in the Mexican Central Plateau, where it poses a threat to native species. Here, we evaluated twospot livebearer sociability towards either a conspecific pair or a shoal of four fish with one of four possible compositions, all conspecifics or two conspecifics combined with either two guppies, two porthole livebearers or two twoline skiffias. In a second experiment, foraging time, latency to feed, first fish to begin foraging and aggressive interactions were recorded under the same social conditions used in the sociability experiment, with body size included as a covariate in both experiments. All focal twospot livebearers spent significantly more time with the given shoals rather than with the available space in the aquarium. They showed a higher tendency to associate with small shoals of conspecifics than with pairs. Larger twospot livebearers associated more, regardless of the social condition. Twospot livebearer fed more with porthole livebearers, less with guppies and similarly with twoline skiffias. Latency to forage did not vary significantly between social conditions. Twospot livebearers were involved in more aggressive interactions when with guppies or porthole livebearers than when with native twoline skiffias or conspecifics. Twospot livebearers could gain benefits from associating with natives and conspecifics, but not with other invasive poeciliids. Heterospecific shoaling behaviour with natives may enhance invasion success during early stages when conspecifics are scarce while associating with other invasive poeciliids could lead to increased competition. Further research is needed on heterospecific interactions of non‐natives to better understand their behavioural role in invasion likelihood. [ABSTRACT FROM AUTHOR]

As cosmological simulations have grown in size, the permanent storage requirements of their particle data have also grown. Even modest simulations present a major logistical challenge for the groups which run these boxes and researchers without access to high performance computing facilities often need to restrict their analysis to lower quality data. In this paper, we present guppy , a compression algorithm and code base tailored to reduce the sizes of dark matter-only cosmological simulations by approximately an order of magnitude. guppy is a 'lossy' algorithm, meaning that it injects a small amount of controlled and uncorrelated noise into particle properties. We perform extensive tests on the impact that this noise has on the internal structure of dark matter haloes, and identify conservative accuracy limits which ensure that compression has no practical impact on single-snapshot halo properties, profiles, and abundances. We also release functional prototype libraries in C, Python, and Go for reading and creating guppy data. [ABSTRACT FROM AUTHOR]

Potential toxicity of treated effluents of selected natural rubber processing industries was evaluated by integrating physicochemical analysis with Daphnia magna and Poecilia reticulata bioassays as ecotoxicity tools. Further, the efficacy of the constructed wetland treatments practiced by the industries for reducing the ecotoxicity of the final effluents reaching the receiving water course was assessed. Even after passing through the constructed wetlands, some of the measured physicochemical parameters of the final effluents did not comply with the stipulated rubber processing effluent regulatory limits. Acute toxicity data of treated effluents demonstrated greater susceptibility of D. magna compared to P. reticulata. Erythrocytic abnormality tests with P. reticulata revealed that rubber industry effluents contained cytogenotoxic contaminations which had not been completely eliminated by the treatment processes. Wetland treatment technique was not effective in reducing the cytogenotoxic effects of final effluents reaching the receiving water course. The use of ecotoxicity tools for optimization of rubber industry effluent treatment processes would help to reduce potential toxic/cytogenotoxic effects of effluent receiving waterbodies considering sustainable development goals focusing on ecosystem safety. [ABSTRACT FROM AUTHOR]

Dispersal is critical to population persistence, colonization and connectivity which are all critical components of invasive success. While individual propensity to disperse varies within populations, the underlying mechanisms promoting individual dispersal remain unclear. Collectively, dispersal is influenced by the environment and individual phenotype. Here we investigated individual dispersal propensity in the Trinidadian guppy, Poecilia reticulata , and related individual variation in dispersal behaviour to phenotype and social/environmental conditions. Namely, we addressed the effect of sex ratio (social/environmental factor) on the tendency for individuals to disperse across physical barriers via jumping behaviour. Jumping is vital for the dispersal of many aquatic species and has been anecdotally linked to the guppy's global invasive success. We found similar jumping behaviour for males and females, with population sex ratio not influencing the magnitude of male or female dispersal. Further, we found consistent among-individual variation in jumping probability; individual differences explained 17.46% and 7.92% of total variation in jumping probability for males and females, respectively. These results strongly indicate that sex ratio does not influence jumping behaviour, suggesting that species invasions are mediated by a nonrandom subset of individuals with greater dispersal tendencies. Overall, this study stresses the need to move the focus of invasion biology from the species level to incorporate information on individual variation in behaviour. • Guppies differ in individual propensity to disperse over physical barriers. • Sex ratio does not influence jumping behaviour. • Species invasions are mediated by individuals with greater dispersal tendencies. [ABSTRACT FROM AUTHOR]

The guppy, Poecilia reticulata, is one of the most common cultured ornamental fish species, and a popular pet fish highly desired by hobbyists worldwide due to its availability of many brilliantly coloured fish of many varieties. The susceptibility of guppies to diseases presents a remarkable concern for both breeders and hobbyists. In this study, we report the emergence of disease in fancy guppies caused by a previously uncharacterized virus in the USA. This virus was isolated from moribund guppies in two separate outbreaks in California and Alabama, from December 2021 to June 2023. The infected guppies presented with acute morbidity and mortality shortly after shipping, displaying nonspecific clinical signs and gross changes including lethargy, anorexia, swimming at the water surface, gill pallor, mild to moderate coelomic distension and occasional skin lesions including protruding scales, skin ulcers and hyperaemia. Histological changes in affected fish were mild and nonspecific; however, liver and testes from moribund fish were positive for Tilapia lake virus (TiLV), the single described member in the family Amnoonviridae, using immunohistochemistry and in situ hybridization, although the latter was weak. A virus was successfully recovered following tissue inoculation on epithelioma papulosum cyprini and snakehead fish cell lines. Whole genome sequencing and phylogenetic analyses revealed nucleotide and amino acid homologies from 78.3%–91.2%, and 78.2%–97.7%, respectively, when comparing the guppy virus genomes to TiLV isolates. Based on the criteria outlined herein, we propose the classification of this new virus, fancy tailed guppy virus (FTGV), as a member of the family Amnoonviridae, with the name Tilapinevirus poikilos (from the Greek 'poikilos', meaning of many colours; various sorts, akin to 'poecilia'). [ABSTRACT FROM AUTHOR]

Guppy fish (Poecilia reticulata) is an ornamental fish in great demand because of its small size and beautiful color. The color of ornamental fish will generally fade due to a lack of carotenoids in their feed. This study aimed to determine the effect of giving Tubifex sp. in commercial feed to increase the color intensity of guppy fish and the best dose of Tubifex sp. The test fish used were male guppy fish strain HB Red. This study used a completely randomized design (CRD) method with five treatments and three replications, that is, commercial feed with the addition of Tubifex sp. with doses of 0% (P1), 2% (P2), 4% (P3), 6% (P4), and 8% (P5). The parameters observed were color intensity (chroma value), survival, and water quality. The addition of Tubifex sp. in commercial feed gave the effect with the highest yield on P5 at a dose of 8%, with an increase in color intensity (chroma value) of 4,21±0,25d. At P1, it gave an increase of 1,19±0,02a, P2 was 1,34±0,04a, P3 was 1,81±0,21b, and P4 was 2,88±0,18c. So, the best treatment is P5 (8%). Survival showed the results were not significantly different, that is, 100%. Water quality is included in the tolerance limit of fish with the results of temperature 26,6 - 27,4°C, pH 7,4 - 7,9, and DO 6,2 - 7,7 mg/L. [ABSTRACT FROM AUTHOR]

Environmental change can alter predator-prey dynamics. However, studying predators in the context of co-occurring environmental stressors remains rare, especially under field conditions. Using in situ filming, we examined how multiple stressors, including temperature and turbidity, impact the distribution and behaviour of wild fish predators of Trinidadian guppies (Poecilia reticulata). The measured environmental variables accounted for 17.6% of variance in predator species composition. While predator species differed in their associations with environmental variables, the overall prevalence of predators was greatest in slow flowing, deeper, warmer and less turbid habitats. Moreover, these warmer and less turbid habitats were associated with earlier visits to the prey stimulus by predators, and more frequent predator visits and attacks. Our findings highlight the need to consider ecological complexity, such as co-occurring stressors, to better understand how environmental change affects predator-prey interactions. Field observations show that fish predators exhibit stronger association with warmer, still, clear waters. Here they exert heightened predation pressure on prey fish, highlighting the importance of ecological context in predator-prey dynamics. [ABSTRACT FROM AUTHOR]

Behavioural and physiological resistance are key to slowing epidemic spread. We explore the evolutionary and epidemic consequences of their different costs for the evolution of tolerance that trades off with resistance. Behavioural resistance affects social cohesion, with associated group-level costs, while the cost of physiological resistance accrues only to the individual. Further, resistance, and the associated reduction in transmission, benefit susceptible hosts directly, whereas infected hosts only benefit indirectly, by reducing transmission to kin. We therefore model the coevolution of transmission-reducing resistance expressed in susceptible hosts with resistance expressed in infected hosts, as a function of kin association, and analyse the effect on population-level outcomes. Using parameter values for guppies, Poecilia reticulata, and their gyrodactylid parasites, we find that: (1) either susceptible or infected hosts should invest heavily in resistance, but not both; (2) kin association drives investment in physiological resistance more strongly than in behavioural resistance; and (3) even weak levels of kin association can favour altruistic infected hosts that invest heavily in resistance (versus selfish tolerance), eliminating parasites. Overall, our finding that weak kin association affects the coevolution of infected and susceptible investment in both behavioural and physiological resistance suggests that kin selection may affect disease dynamics across systems. [ABSTRACT FROM AUTHOR]

For many mammalian and avian species, it has been proposed that cognitive enrichment, such as puzzle feeders, can improve welfare in captive conditions. A well‐established method to evaluate the need for cognitive enrichment is to observe the preference of the animal between freely available food and a puzzle feeder. We investigated this preference in a teleost fish, the guppy. In most of our experimental trials, guppies first chose the feeder with freely available food over the puzzle feeder, in contrast with what was observed in most other species. Nevertheless, the guppies' number of choices for the puzzle feeder was significantly greater than zero. Moreover, after consuming the freely available food, most of the guppies tackled the puzzle feeder. This pattern of results suggests that guppies displayed a certain interest in the puzzle feeder that was overshadowed by their strong attraction towards the free food. Interestingly, several measures of performance indicated that female guppies responded more positively towards the puzzle feeder as compared to the males, suggesting sex differences in the preference for cognitive enrichment. In conclusion, our study highlights the potential significance of cognitive enrichment for captive fish. Considering that the number of individual fish maintained in captivity exceeds by far that of any other vertebrate group, it is paramount to investigate cognitive enrichment in other teleost species. [ABSTRACT FROM AUTHOR]

The presence of bystanders can influence the behavior of a forager, which has mainly been studied in primates and birds. We tested the effect of the absence and presence of an unfamiliar audience (females, males, and their combination) near or far from a food patch on the foraging behavior of guppies (Poecilia reticulata). Our investigation includes both males and females, recognizing that different social dynamics and reproductive strategies between the sexes could lead to varied responses to audience effects. For each focal fish, we measured the latency to start feeding, bite frequency, time spent near the audience, and overall mobility. Both males and females started feeding faster when food was close to any audience type. Specifically, females exhibited a faster feeding response in the presence of a female audience. Males reduced their feeding rate in the presence of male and mixed audiences, while both sexes increased their consumption when food was close to the audience. Focal fish, irrespective of their sex, spent more time in the vicinity of the audience zone when the audience was present, but surprisingly, females spent less time with a female audience compared to others. Only females increased their mobility when the food patch was far from any audience. Here, we show that guppies adjust their foraging behavior in the presence of an audience. The specific responses observed varied between the sexes, reflecting the distinct social trade-offs faced by each sex. [ABSTRACT FROM AUTHOR]

Diverse clades of fishes adapted to feeding on the benthos repeatedly converge on steep craniofacial profiles and shorter, wider heads. But in an incipient radiation, to what extent is this morphological evolution measurable and can we distinguish the relative genetic vs. plastic effects? We use the Trinidadian guppy (Poecilia reticulata) to test the repeatability of adaptation and the alignment of genetic and environmental effects shaping poecilid craniofacial morphology. We compare wild-caught and common garden lab-reared fish to quantify the genetic and plastic components of craniofacial morphology across 4 populations from 2 river drainage systems (n  = 56 total). We first use micro-computed tomography to capture 3D morphology, then place both landmarks and semilandmarks to perform size-corrected 3D morphometrics and quantify shape space. We find a measurable, significant, and repeatable divergence in craniofacial shape between high-predation invertivore and low-predation detritivore populations. As predicted from previous examples of piscine adaptive trophic divergence, we find increases in head slope and craniofacial compression among the benthic detritivore foragers. Furthermore, the effects of environmental plasticity among benthic detritivores produce exaggerated craniofacial morphological change along a parallel axis to genetic morphological adaptation from invertivore ancestors. Overall, many of the major patterns of benthic-limnetic craniofacial evolution appear convergent among disparate groups of teleost fishes. [ABSTRACT FROM AUTHOR]

Background: Exotic and ornamental fish are highly popular companion animals resulting in a significant transcontinental trade of fish, invertebrates and aquatic plants. A major issue is the diseases associated with these organisms, as they have a major impact on health of the fish in both public and private household aquaria. A secondary issue is the trade with these products, which potentially may expand the distribution area and spread a range of diseases to new habitats. Results: We here describe how Poecilia reticulata (guppy), produced in a private household aquarium, were invaded by cercariae of an exotic trematode released by imported Melanoides tuberculata snails. The fish presented with severe clinical signs (tremor, flashing, scraping of body against objects). A standard parasitological examination and morphometric identification showed scale pocket infections with a digenean trematode species within the genus Transversotrema. Molecular identification by PCR, sequencing and phylogenetic analyses of a 2646 bp sequence encoding ribosomal RNA (partial 18 S, ITS1, 5.8 S, ITS2, partial 28 S) was performed. The 1107 bp sequence of mitochondrial DNA (cox1) showed that the parasite differed from previously described Transversotrema species in M. tuberculata. Morphometrics of adult and larval specimens of this isolate also differed from previously described freshwater species within the genus. The new species was described and is named after Copenhagen, for its geographic origin. Conclusions: The genus Transversotrema comprises a range of species, adapted to a microhabitat in scalepockets of teleosts. A combination of morphological and molecular characterization techniques has been shown to provide a good differentiation between species. The fish were not purchased from a pet shop but produced in the home aquarium. This indicated that an infection pressure existed in the aquarium, where the source of infection was found to be exotic intermediate host snails M. tuberculata, which originally were imported and purchased from a pet shop. The potential spread of fish diseases associated with trade of fish and snails to new geographic regions, where climate conditions are favourable, is discussed. [ABSTRACT FROM AUTHOR]

One hundred and twenty red fantail male guppies (Poecilia reticulata) with an average weight of 0.64 ± 0.07 g were fed ad libitum a control diet without any herbals (0), 20 g/kg garlic, 20 g/kg red onion, and 20 g/kg sweet red pepper powders in 12 circular tanks for 60 d. The herbal treatments had significantly higher weight gain (94.70 ± 0.89 to 96.26 ± 0.90%), protein (3.58 ± 0.05 to 3.72 ± 0.06 mg/ml), ACH50 (1.41 ± 0.00 to 1.56 ± 0.00 U/ml), Ig (0.16 ± 0.00 to 0.32 ± 0.02 mg/ml), lysozyme activity (60.33 ± 0.88 to 68.00 ± 1.15 U/ml), carotenoids in lateral skin body (5.75 ± 0.025 to 8.26 ± 0.003 µg/g), and caudal fin (6.49 ± 0.003 to 10.10 ± 0.005 µg/g) than the control. Therefore, dietary garlic and sweet red pepper can be used for immunity and coloration in red fantail male guppies. [ABSTRACT FROM AUTHOR]

Cooperative behaviours, which benefit a recipient, are widespread in the animal kingdom; yet their evolution is not straightforward. Reciprocity, i.e., cooperating with previously experienced cooperative partners, has been suggested to underly cooperation, but has been contested throughout the years. Once a textbook example of reciprocity was cooperative predator inspection, where one or several individuals leave their group to approach a potential threat. Each can at any point stop or retreat, increasing the risk for its partner. It was suggested that inspecting individuals follow a specific reciprocal strategy called tit‐for‐tat, i.e., cooperating on the first move and then copying the partner's last move. Numerous studies provide evidence to support the claim that fish cooperate to inspect predators, including three‐spined sticklebacks (Gasterosteus aculeatus), guppies (Poecilia reticulata) and minnows (Phoxinus phoxinus). However, over the past few decades some scholars have expressed scepticism whether predator inspection is indeed a cooperative behaviour or rather a case of by‐product mutualism, which describes behaviours that benefit a partner as a corollary of an otherwise selfish behaviour. For instance, it has been shown that pairs of fish moving in unfamiliar environments appear to coordinate movements even in the absence of predators. Many studies have also used coarse measures of overall approach rates towards predators rather than the fine‐grained analyses necessary to infer tit‐for‐tat in cooperative inspections. Now is the time to return to the question of cooperative predator inspection with new tools and approaches to resolve a decades‐old debate. [ABSTRACT FROM AUTHOR]

Generally, in vertebrates, the first step toward fertilization is the ovulation of mature oocytes, followed by their binding to sperm cells outside of the ovary. Exceptionally, the oocytes of poeciliid fish are fertilized by sperm cells within the follicle, and the developmental embryo is subsequently released into the ovarian lumen before delivery. In the present study, we aimed to identify the factor(s) responsible for intrafollicular fertilization in a viviparous teleost species, Poecilia reticulata (guppy). Sperm tracking analysis in this regard indicated that in this species, sperm cells reached immature oocytes including the germinal vesicle, and the insemination assay indicated that the immature oocytes robustly adhered to the sperm cells; similar binding was not observed in Danio rerio (zebrafish) and Oryzias latipes (medaka). We also identified the Ly6/uPAR protein bouncer as the factor responsible for the observed sperm binding activity of the immature oocytes in this species. The recombinant bouncer peptide acted as an inhibitory decoy for the sperm–oocyte binding in guppy. On the other hand, ectopic expression of guppy bouncer in zebrafish oocytes resulted in interspecific sperm–oocyte binding. These results argue that bouncer is responsible for sperm–immature oocyte binding. Our findings highlight the unique reproductive strategies of guppy fish and enhance our understanding of the diverse reproductive mechanisms in vertebrates. [ABSTRACT FROM AUTHOR]

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Simple Summary: This study examined the synergistic effect of eugenol and 1,8-cineole (eucalyptol) on anesthesia in female guppy fish. The results showed that eugenol induced fish anesthesia at concentrations of 50 and 70 mg/L, with durations of 256.5 and 171.5 s, respectively. 1,8-cineole did not induce fish anesthesia. Combining eugenol with 1,8-cineole resulted in the faster induction of anesthesia and a longer recovery time. This study concluded that eugenol and 1,8-cineole work better together as anesthetics, demonstrating the safety of using these agents on guppy fish. This study aimed to evaluate the synergistic effect between eugenol and 1,8-cineole on anesthesia in female guppy fish (Poecilia reticulata). Experiment I evaluated the concentrations of 0, 12.5, 25, 50, and 75 mg/L of eugenol and 0, 100, 200, 300, and 400 mg/L of 1,8-cineole for times of induction and recovery from anesthesia. Experiment II divided fish into 16 study groups, combining eugenol and 1,8-cineole in pairs at varying concentrations, based on the dosage of the chemicals in experiment I. The results of the anesthesia showed that eugenol induced fish anesthesia at concentrations of 50 and 70 mg/L, with durations of 256.5 and 171.5 s, respectively. In contrast, 1,8-cineole did not induce fish anesthesia. In combination, using eugenol at 12.5 mg/L along with 1,8-cineole at 400 mg/L resulted in fish anesthesia at a time of 224.5 s. Increasing the eugenol concentration to 25 mg/L, combined with 1,8-cineole at 300 and 400 mg/L, induced fish anesthesia at times of 259.0 and 230.5 s, respectively. For treatments with eugenol at 50 mg/L combined with 1,8-cineole at 100 to 400 mg/L, fish exhibited anesthesia at times of 189.5, 181.5, 166.0, and 157.5 s. In the case of eugenol at 75 mg/L, fish showed anesthesia at times of 175.5, 156.5, 140.5, and 121.5 s, respectively. The testing results revealed that 1,8-cineole as a single treatment could not induce fish anesthesia. However, when supplementing 1,8-cineole in formulations containing eugenol, fish exhibited a significantly faster induction of anesthesia (p < 0.05). Furthermore, all fish that underwent anesthesia were able to fully recover without any mortality. However, the shorter anesthesia duration resulted in a significantly prolonged recovery time. In conclusion, eugenol and 1,8-cineole work better together as anesthetics than when used separately, and demonstrated the safety of using these anesthetic agents on guppy fish. [ABSTRACT FROM AUTHOR]

Food quality (e.g. the presence of cyanobacteria) may affect the behavior, morphology and life history of cladocerans. However, little is known about how diet quality may affect the effectiveness of Daphnia 's behavioral defenses against predators. Here we test the hypothesis that the presence of non-toxic cyanobacteria in Daphnia 's diet reduces its ability to escape fish attack. The animals cultured under two different food quality regimes (green alga vs. cyanobacteria) were subjected to two types of predation experiments. In the first, we tested Daphnia 's ability to avoid a predator whose feeding was simulated using a pipette, while in the second we tested Daphnia 's ability to escape when confronted with a foraging fish (Poecilia reticulata). In both types of experiments, the ability to avoid predator attack was greater in Daphnia fed high quality green algae than in Daphnia fed low quality cyanobacteria.. We conclude that low food quality can affect the fitness of Daphnia not only by slowing their growth and reproduction rates, but also by increasing their susceptibility to predation. [ABSTRACT FROM AUTHOR]

Evolutionary biologists have long been interested in parsing out the roles of genetics, plasticity and their interaction on adaptive trait divergence. Since males and females often have different ecological and reproductive roles, separating how their traits are shaped by interactions between their genes and environment is necessary and important. Here, we disentangle the sex-specific effects of genetic divergence, developmental plasticity, social learning and contextual plasticity on foraging behaviour in Trinidadian guppies (Poecilia reticulata) adapted to high- or low-predation habitats. We reared second-generation siblings from both predation regimes with or without predator chemical cues, and with adult conspecifics from either high- or low-predation habitats. We then quantified their foraging behaviour in water with and without predator chemical cues. We found that high-predation guppies forage more efficiently than low-predation guppies, but this behavioural difference is context-dependent and shaped by different mechanisms in males and females. Higher foraging efficiency in high-predation females is largely genetically determined, and to a smaller extent socially learned from conspecifics. However, in high-predation males, higher foraging efficiency is plastically induced by predator cues during development. Our study demonstrates sex-specific differences in genetic versus plastic responses in foraging behaviour, a trait of significance in organismal fitness and ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Behavioural plasticity allows organisms to respond to environmental challenges on short time scales. But what are the ecological and evolutionary processes that underlie behavioural plasticity? The answer to this question is complex and requires experimental dissection of the physiological, neural and molecular mechanisms contributing to behavioural plasticity as well as an understanding of the ecological and evolutionary contexts under which behavioural plasticity is adaptive. Here, we discuss key insights that research with Trinidadian guppies has provided on the underpinnings of adaptive behavioural plasticity. First, we present evidence that guppies exhibit contextual, developmental and transgenerational behavioural plasticity. Next, we review work on behavioural plasticity in guppies spanning three ecological contexts (predation, parasitism and turbidity) and three underlying mechanisms (endocrinological, neurobiological and genetic). Finally, we provide three outstanding questions that could leverage guppies further as a study system and give suggestions for how this research could be done. Research on behavioural plasticity in guppies has provided, and will continue to provide, a valuable opportunity to improve understanding of the ecological and evolutionary causes and consequences of behavioural plasticity. [ABSTRACT FROM AUTHOR]

The high-elevation plateaus of the inter-Andean valleys are home to shallow lakes that have become eutrophic. These lakes share similarities with shallow lakes in temperate and subtropical areas. Because native species diversity is low, invasive species dominate the fish and macrophytes communities. The study aimed to investigate the behavioral response of the local Daphnia pulex from the Andean shallow Lake Yahuarcocha to the exotic submerged macrophyte Egeria densa and the exotic fish Poecilia reticulata. Laboratory habitat choice experiments revealed that D. pulex from Lake Yahuarcocha strongly avoid E. densa, irrespective of the presence of the fish P. reticulata or chemical cues indicating fish predation on D. pulex. This observation could be explained by the fact that P. reticulata displayed a strong attraction to E. densa during the daytime, probably to avoid bird predation. D. pulex from the nearby Lake San Pablo where P. reticulata is absent but where the fish community is dominated by Oncorhynchus mykiss displayed the same avoidance behavior to submerged macrophytes as D. pulex from Lake Yahuarcocha. These results indicate that macrophytes in these high-elevation shallow lakes may not facilitate top-down control of phytoplankton, since plants do not offer refuge to D. pulex from fish predation. [ABSTRACT FROM AUTHOR]

Environmental influences on species' functional traits are important ecological issues to assess biodiversity. Relationships among fish abundance, their functional traits, and environmental conditions across different levels of anthropogenic impacts in a tropical Brazilian river were evaluated. We combined RLQ and fourth-corner methods, utilizing local environmental variables and the Human Footprint Index (HFI) as a human activities indicator. Three HFI levels (High, Intermediate, and Low) and short-term (1993–2009) impact changes at each location were assigned. Fish with internal fertilization and small body sizes were strongly associated with high HFI scores. Grass-dominated riparian areas were common in altered locations, whereas less altered localities exhibited the riparian cover dominated by trees. Highly altered areas showed high HFI, grass-covered riparian zones, and small-sized species with internal fertilization (e.g., Cyprinodontiformes like Poecilia vivipara, Poecilia reticulata, and Phalloceros caudimaculatus). In contrast, less altered areas had tree-lined riparian zones and medium to large-sized species with external fertilization and diverse traits. Underlying deterministic processes shape species distribution, tied to environment and traits. Filtering of traits in the most altered locations may favor small-sized species with internal fertilization. This approach, utilizing HFI and local variables to assess trait–environment relationships of riverine fish, facilitates understanding organisms' responses to environmental constraints. [ABSTRACT FROM AUTHOR]