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Numerical discrimination is widespread in vertebrates, but this capacity varies enormously between the different species examined. The guppy (Poecilia reticulata), the only teleost examined following procedures that allow a comparison with the other vertebrates, outperforms amphibians, reptiles and many warm-blooded vertebrates, but it is unclear whether this is a feature shared with the other teleosts or represents a peculiarity of this species. We trained zebrafish (Danio rerio) to discriminate between numbers differing by one unit, varying task difficulty from 2 versus 3 to 5 versus 6 items. Non-numerical variables that covary with number, such as density or area, did not affect performance. Most fish reached learning criterion on all tasks up to 4 versus 5 discrimination with no sex difference in accuracy. Although no individual reached learning criterion in the 5 versus 6 task, performance was significant at the group level, suggesting that this may represent the discrimination threshold for zebrafish. Numerosity discrimination abilities of zebrafish compare to those of guppy, being higher than in some warm-blooded vertebrates, such as dogs, horses and domestic fowl, though lower than in parrots, corvids and primates. Learning rate was similar in a control group trained to discriminate between different-sized shapes, but zebrafish were slightly more accurate when discriminating areas than numbers and males were more accurate than females. At the end of the experiment, fish trained on numbers and controls trained on areas generalized to the reciprocal set of stimuli, indicating they had used a relational strategy to solve these tasks.

Here, I report an unexpected interaction between the introduced fish species, Poecilia (Mollienesia) latipinna and humans in Lake Vouliagmeni, Greece. In this lake, I observed the normally skittish P. latipinna approach and graze on the exposed skin of bathing humans, presumably removing dead skin cells in what amounts to an exfoliating process. The natural occurrence of this phenomenon in Lake Vouliagmeni is likely a product of multiple contingencies, including the introduction of P. latipinna sometime around the mid-twentieth century, and the fairly unique ecological circumstances. I suggest and discuss several conditions that must be met for such a cleaning interaction to develop, including an appropriate fish species being present, an environment in which fish are able to safely approach humans without being captured or otherwise harmed, and human tolerance—even enjoyment—of the behavior. Finally, I point out a number of remaining questions including whether both species receive a net benefit, if there has been any behavioral or physiological feeding specialization, and whether similar phenomena occur elsewhere in the world.

Male guppies display an outstanding diversity of color patterns which is formed as a result of a complex interplay between sexual selection, predation, and other environmental factors. The heterogeneity of the environment affects the variability of ornamental traits in male guppies through genotype–environment interaction. Thyroid hormones (THs) are important regulators of the ontogeny of fish and serve as a link between environmental changes and phenotypic development. However, the role of THs in the formation of a variety of color patterns in male guppies remained poorly understood. In this work, an experimental assessment of the effect of THs on the variability of ornamental traits in Poecilia wingei males was carried out. The fish were reared from birth to the initial stages of the formation of melanistic elements in males and until the final formation of the color pattern; they were subjected to different hormonal regimes: euthyroidism (natural TH status), hyperthyroidism (high TH level, at a triiodo-L-thyronine concentration of 0.15 μg/mL), and hypothyroidism (TH-deficiency, at a thiourea concentration of 0.025%). Alterations in the TH status caused changes in the timing and rate of the development of coloration and affected the transformation of various elements of the color pattern in males. These changes led to an increase in phenotypic variability and the appearance of ornamental traits in the male color patterns that were characteristic of closely related species of Poecilia. Thus, the data obtained indicate a potentially important role of thyroid hormones in the diversification of guppy color patterns and open up new prospects for studying the role of endocrine regulatory mechanisms in the adaptive evolution of poeciliid fish.

The ecological consequences of biological range extensions reflect the interplay between the functional characteristics of the newly arrived species and their recipient ecosystems. Teasing apart the relative contribution of each component is difficult because most colonization events are studied retrospectively, i.e., after a species became established and its consequences apparent. We conducted a prospective experiment to study the ecosystem consequences of a consumer introduction, using whole-stream metabolism as our integrator of ecosystem activity. In four Trinidadian streams, we extended the range of a native fish, the guppy (Poecilia reticulata), by introducing it over barrier waterfalls that historically excluded it from these upper reaches. To assess the context dependence of these range extensions, we thinned the riparian forest canopy on two of these streams to increase benthic algal biomass and productivity. Guppy's range extension into upper stream reaches significantly impacted stream metabolism but the effects depended upon the specific stream into which they had been introduced. Generally, increases in guppy biomass caused an increase in gross primary production (GPP) and community respiration (CR). The effects guppies had on GPP were similar to those induced by increased light level and were larger in strength than the effects stream stage had on CR. These results, combined with results from prior experiments, contribute to our growing understanding of how consumers impact stream ecosystem function when they expand their range into novel habitats. Further study will reveal whether local adaptation, known to occur rapidly in these guppy populations, modifies the ecological consequences of this species introduction.

Biological invasion is globally pervasive and an increasing threat to biodiversity. We need to be able to predict the ecological impacts of alien species, in order to prioritize management of those expected to be most damaging. Comparisons of functional response (FR) between invaders and trophically similar natives has been proposed as useful for predicting invader impacts, as interaction intensity tends to be reflected in higher FRs. We undertook feeding trials comparing FRs of four invasive poeciliids (mosquitofish [Gambusia affinis], guppy [Poecilia reticulata], liberty molly [P. salvatoris] and swordtail [Xiphophorus hellerii]) in Hong Kong with three similar-sized native fishes (ricefish [Oryzias curvinotus: Adrianichthyidae]; predaceous chub [Parazacco spilurus] and half-banded barb [Puntius semifasciolatus: Cyprinidae]). We tested whether FRs correctly reflected known impacts of the mosquitofish and guppy locally, and used FRs to forecast potential impacts of the molly and swordtail. Overall, the swordtail and molly consumed more prey and had higher FRs than the other five fishes, owing to their shorter prey handling time and/or higher attack rate. Mosquitofish and guppy had similar FRs to native fishes. All fishes showed type-II FRs, and had some potential to destabilize prey populations. Such results predict that the molly and swordtail could have strong ecological effects in Hong Kong freshwaters. However, FR alone was not highly predictive of known impacts of mosquitofish and guppy. It is suggested a more holistic approach incorporating estimates of field abundance and parameterization of other niche dimensions of the invader will be needed.

The effects of invaders on native species are usually tested using species mean trait values over long time scales. However, considering individual variation over short timescales can help us better understand the interaction between invaders and native species. We compared trophic traits of the non-native guppy (Poecilia reticulata) and the native Brazilian poeciliid Phalloceros harpagos using experiments simulating the early stages of an invasive process. We used short-term mesocosms to simulate an early invasion scenario, where the two species were placed together, and a pre-invasion scenario, where species were kept separated, and analyzed interspecific and intraspecific trophic variability. We also compared the foraging efficiency of species in laboratory experiments. We found no differences on the mean diet of both species between pre and early invasion treatments. At the individual level, in the early invasion scenario, individuals of both species reduced their trophic niche as a probable effect of the presence of the heterospecific. Phalloceros harpagos had higher consumption rates than guppies indicating greater efficiency in feeding on invertebrates. Our results suggest that non-native species were not intrinsically better consumers of high-quality resources. Instead, intraspecific variation might be playing an overlooked role in shaping interactions between species during the early stages of invasion.

Pro-social effects of oxytocin and its homologues are well-documented in birds and mammals. However, in fishes, the effect of isotocin, the homologue of oxytocin, on social behaviour is less clear. Studies in fishes have generally shown no effect of isotocin on social behaviours or even an anti-social effect. In our study, we measured association preference for conspecifics in 92 adult guppies (46 females and 46 males), half of which were injected with isotocin and the other half with an isotocin antagonist. We found that individuals injected with isotocin spent 29% more time associating with conspecifics than individuals injected with an isotocin antagonist. The effect of isotocin on association time did not differ between males and females. Our study provides some of the first evidence of a pro-social effects of isotocin in a fish and suggests that in fishes, isotocin may have a homologous role to oxytocin, at least in promoting shoaling behaviour.

A major advantage of animal aggregations concerns cooperative antipredator strategies. Schooling behavior emerges earlier in many fish species, especially in those cannibalizing their offspring. Experience is fundamental for developing schooling behavior. However, the cognitive ability of naive newborn fish to aggregate remains unclear. Herein, Poecilia reticulata, was selected as model organism to investigate how combinations of biomimetic robotic agents and adult conspecific olfactory cues affect collective responses in newborns. The role of white and brown backgrounds in evoking aggregations was also assessed. Olfactory cues were sufficient for triggering aggregations in P. reticulata newborns, although robotic agents had a higher influence on the group coalescence. The combination of robotic agents and olfactory cues increased schooling behavior duration. Notably, schooling was longer in the escape compartment when robotic agents were presented, except for the combination of the male-mimicking robotic fish plus adult guppy olfactory cues, with longer schooling behavior in the exploring compartment. Regardless of the tested cues, newborn fish aggregated preferentially on the brown areas of the arena. Overall, this research provides novel insights on the early collective cognitive ability of newborn fish, paving the way to the use of biomimetic robots in behavioral ecology experiments, as substitutes for real predators.

Aeromonas spp. are opportunistic pathogenic bacteria related to an assembly of infectious diseases in ornamental fish. In the present study, virulence properties and antibiotic susceptibility of 52 guppy-borne Aeromonas spp. were investigated. The isolates were identified as A. veronii (n = 34), A. dhakensis (n = 10), A. hydrophila (n = 3), A. caviae (n = 3) and A. enteropelogenes (n = 2) by gyrB gene sequencing. The gyrB sequence deviation within and among the species ranged from 0 to 2.6% and 2.7-9.2%. Each species formed a distinct group in the unrooted neighbor-joining phylogenetic tree. The phenotypic virulence factors such as β-hemolysis, slime, caseinase, DNase, gelatinase and lipase production were observed in 28 (53.9%), 33 (63.5%), 28 (53.9%), 42 (80.8%), 37 (71.2%) and 42 (80.8%) isolates, respectively. The virulence genes were detected by PCR assay in the following proportions- act (84.6%), hly (80.8%), aer (73.1%), lip (73.1%), gcaT (73.1%), ascV (53.8%), ahyB (53.8%) fla (51.9%), alt (48.1%), ast (36.5%) and ser (34.6%), respectively. The amoxicillin, ampicillin, imipenem, nalidixic acid, oxytetracycline and rifampicin were resistant to more than 70.0% of the isolates in antibiotic susceptibility test. Our study suggests that the ornamental guppy can be a potential reservoir of virulent and multi-drug resistant Aeromonas spp.

In this study, silver nanoparticle was green synthesized using the leaf extract of Solanum nigrum (Sn-AgNPs) and bio-physically characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HR-TEM), Zeta potential analysis and Energy dispersive X-ray (EDX) analysis. The ecotoxicity of silver nanoparticle (Sn-AgNPs) were tested against both invertebrate (Ceriodaphnia cornuta and Paramecium sp.) and vertebrate aquatic animal models (Guppy fish, Poecilia reticulata) in comparison with bare silver nitrate. Sn-AgNPs were observed to be less toxic than ionic silver (silver nitrate). The ecotoxicity levels of Sn-AgNPs were found to be varied between tested organisms. Sn-AgNPs caused 100% mortality of freshwater crustacean, C. cornuta at 50 µg mL−1. At concentration below 50 µg mL−1 (10–30 µg mL−1), abnormality in the swimming behavior of C. cornuta was noticed. The ingestion and accumulation of Sn-AgNPs in the intestine of C. cornuta neonates were visualized under light and confocal laser scanning microscopic images. The ecotoxicity of Sn-AgNPs to the freshwater protozoan ciliate, Paramecium sp. showed that 30 µg mL−1 were lethal and produced 100% mortality at the same concentration. The study concludes that Sn-AgNPs was less toxic to both invertebrate and vertebrate models compared to ionic silver nitrate.

A fundamental question in behavioural and evolutionary ecology is to what degree individual phenotypic traits are variable over time and across ecological contexts and whether they are correlated with each other, as (co)variation in traits determines in part their responses to selection and rate of evolution. A first step to addressing this question is to characterize variation in behavioural traits within and among individuals and their covariation in particular ecological contexts. Here, we ascertained whether adult female guppies (Poecilia reticulata), descendants of wild guppies in Trinidad, are consistent or repeatable in their behaviour over time, such that they exhibit individual ‘personalities’ or behavioural types, and whether their personality traits are inter-correlated. Using a repeated-measures design, we twice assayed individual females for each of three ecologically important behavioural traits, Exploration (of a novel environment), Sociability (shoaling with conspecifics) and Boldness (risk taking), under standardized laboratory conditions. We characterized the among-individual (co)variance structure of each behavioural trait measure, and estimated their respective repeatability and the among-individual correlations between these traits using mixed-effects models. All three traits were found to be significantly repeatable and thus can be considered personality traits. None of the estimated correlations between all possible pairings of the three traits were significantly different from zero. Although adult female Trinidadian guppies from our study population exhibited repeatable personality traits, these traits were not inter-correlated (i.e. did not constitute a behavioural syndrome) and were thus independent of each other. Our findings have important implications for the maintenance of behavioural variation within populations and trait evolution.

Chemical pollution of aquatic environments has been increasing in recent times, causing great damage to the ecosystems and to the fishery sector. Pollutants can negatively alter an animals’ life, and in this investigation, we verify if a neutral household detergent, one of the most common aquatic pollutants, causes changes in the behaviour and personality of guppy (Poecilia reticulata). Thirty milligrams per litre of detergent was added to the water of two aquariums and the behaviour of eight adult guppies were recorded using focal method with instantaneous recording of behaviours every 15 s, for 30 min daily. Results showed that the detergent modified the behaviour and the personality of guppies, making them shier and more inactive. Thus, more efficient disposal techniques should be applied or developed to avoid the pollution of aquatic environments.

Animals are often required to estimate object sizes during several fitness-related activities, such as choosing mates, foraging, and competing for resources. Some species are susceptible to size illusions, i.e. the misperception of the size of an object based on the surrounding context, but other species are not. This interspecific variation might be adaptive, reflecting species-specific selective pressures; according to this hypothesis, it is important to test species in which size discrimination has a notable ecological relevance. We tested susceptibility to a size illusion in the guppy, Poecilia reticulata, a fish species required to accurately estimate sizes during mate choice, foraging, and antipredator behaviours. We focussed on the Delboeuf illusion, in which an object is typically perceived to be larger when surrounded by a smaller object. In experiment 1, we trained guppies to select the larger of two circles to obtain a food reward and then tested them using stimuli arranged in a Delboeuf-like pattern. In experiment 2, we tested guppies in a spontaneous food choice task to determine whether the subjective size perception of food items is affected by the surrounding context. Jointly, our experiments indicated that guppies perceived the Delboeuf illusion, but in a reverse direction relative to humans: guppies estimated as larger the stimulus that human perceived as smaller. Our results indicated susceptibility to size illusions also in a species required to perform accurate size discrimination and support previous evidence of variability in illusion susceptibility across vertebrates.

Variation in predation risk can drive variation in fear intensity, the length of fear retention, and whether fear returns after waning. Using Trinidadian guppies, we assessed whether a low-level predation threat could easily re-trigger fear after waning. First, we show that background risk induced neophobia after either multiple exposures to a low-level threat or a single exposure to a high-level threat. However, a single exposure to the low-level threat had no such effect. The individuals that received multiple background exposures to the low-level threat retained their neophobic phenotype over an 8-day post-risk period, and this response was intensified by a single re-exposure to the low-level threat on day 7. In contrast, the neophobia following the single high-level threat waned over the 8-day period, but the single re-exposure to the low-level threat on day 7 re-triggered the neophobic phenotype. Thus, despite the single low-level exposure being insufficient to induce neophobia, it significantly elevated existing fear and re-triggered fear that had waned. We highlight how such patterns of fear acquisition, retention, and rapid re-triggering play an important role in animal ecology and evolution and outline parallels between the neophobic phenotype in fishes and dimensions of post-traumatic stress in humans.

Msb069 primer pairs encompassed region is believed to be associated with a quantitative trait loci (QTL) of dorsal fin length in subgenus Poecilia. However, detailed investigation on Msb069 which originated from Xiphophorus on subgenus Poecilia remains unexplored. In this study, full sequence of Msb069 was characterized by sequencing bioinformatics analysis and gene expression. The sequence analysis of Msb069 primer pairs encompassed region on three species of Poecilia revealed higher number of microsatellite tandem repeats in Poecilia latipinna $$(\hbox {ATG}_{{\textit{16}}})$$ compared to P. sphenops $$(\hbox {ATG}_{{\textit{13--14}}})$$ . There is no notable pattern of ATG tandem repeats discovered in the hybrids. The full sequence of Msb069 is 734 bp in length and showed a 233 bp conserved region between Xiphophorus and Poecilia. BLAST search performed on this sequence revealed no significant similarities. Nonquantitative RT-PCR exhibited the presence of Msb069 transcripts in three different tissues in subgenus Poecilia. Meanwhile, quantitative RT-PCR expression on two different tissues showed relatively higher expression of Msb069 transcript in P. latipinna dorsal fin tissues in both male and female fishes, suggesting a repressive function of this transcript with respect to dorsal fin length. However the exact gene expression event of Msb069 is still unknown and requires further investigation.

Recent studies on consistent individual differences in behavioural tendencies (animal personality) raised the question of whether individual differences in cognitive abilities can be linked to certain personality types. We tested female Atlantic mollies (Poecilia mexicana) in two different classical conditioning experiments. For the first time, we provide evidence for highly consistent individual differences in associative learning speed in fish. We characterized the same individuals for boldness in two experimental situations (latency to emerge from shelter and freezing time after a simulated predator attack) and found high behavioural repeatability. When we tested for a potential correlation between associative learning speed and boldness, however, there was no evidence for a link between them. Our study design included several steps to avoid typical pitfalls of disadvantaging shy individuals during learning tests. We caution that other experimental studies may have suffered from erroneous interpretations due to a more cautious coping style of shy individuals in the respective setup used to assess learning.

Guppies (Poecilia reticulata) are considered a candidate model species for the identification and testing of endocrine-disrupting chemicals. Male guppies may be used to address the challenge of making potential linkages between alterations of biomarkers, both at the cellular and organ level, and adverse outcomes. In the present study, a predictive relationship between sex characteristics and reproductive output was observed in male guppies that underwent a long-term toxicity test with 0.5 μg/L 17β-estradiol administered during the juvenile period. Radioimmunoassay and western blot analyses demonstrated that 17β-estradiol exposure caused a significant increase in testicular 17β-estradiol levels as well as the induction of exposure biomarkers, namely hepatic vitellogenin. Exposure to 17β-estradiol also caused a significant decrease in testosterone levels, which consequently reduced the gonadosomatic index, sperm counts, and the coloration index. These changes of male sexual characteristics further translated into adverse influences on reproduction, as measured by a decrease in offspring production and survival rate. Our results suggest that the above-mentioned sexual characteristics of male guppies may be considered potential in vivo biomarkers of estrogen effects on reproduction.

Guppy (Poecilia reticulata) is a promising model organism in toxicological studies, and vitellogenin (Vtg) is a commonly used biomarker for environmental estrogens. Although an ELISA for guppy Vtg has been developed previously, we found that guppy had two forms of Vtgs. In this study, two Vtgs were characterized and enzyme-linked immunosorbent assays (ELISAs) for each Vtg were developed. Two Vtgs purified from 17β-estradiol (E2)-exposed guppy were characterized as phospholipoglycoproteins with molecular weights of ~ 520 and ~ 480 kDa, respectively. In SDS-PAGE, one purified Vtg appeared as three major bands of ~ 210, ~ 126, and ~ 102 kDa, and the other revealed a clear band of ~ 68 kDa. Matrix-assisted laser desorption/ionization–time of flight/time of flight mass spectrometry analysis showed that they were VtgAb and VtgC. Using purified Vtgs and their corresponding antibodies, two sandwich ELISAs with working ranges of 7.8~1000 and 15.6~500 ng/mL were developed. Precision tests showed that intra- and inter-assay coefficients of variations of both ELISAs were below 10%. Parallelism between Vtg standard curves and serial dilutions of whole body homogenate from E2-exposed guppy confirmed that two ELISAs could quantify guppy Vtgs. Furthermore, two ELISAs were used to measure Vtg inductions in liver, caudal fin and whole body of male guppy exposed to 17a-ethinylestradiol to validate their use for detecting estrogenic effects of exogenous chemicals. These homologous Vtg ELISAs will promote the use of guppy as a model organism to study estrogenic chemicals.

Predators alter abundances and life history characteristics of prey, and effects of predator–prey interactions can be altered by third-party species. Here, we examine size structures of the caddisfly, Phylloicus hansoni, in Trinidadian streams with two distinct fish assemblages: upstream reaches where the predatory killifish, Anablepsoides hartii, is the only fish species (Killifish-Only reaches), and downstream reaches where killifish and the omnivorous guppy, Poecilia reticulata, coexist (Killifish–Guppy reaches). We asked: Do P. hansoni larvae exhibit differences in size structure between reaches with differing fish assemblages? We found that size distributions of larvae differed between reaches in the majority of replicate streams, with smaller median body lengths in Killifish-Only reaches. Killifish–Guppy reaches had higher proportions of the largest instar, but we did not find differences in body length within an instar. No evidence of size-selective predation was found through analysis of killifish stomach contents, and environmental variables were largely similar between upstream and downstream reaches of the five study streams, aside from higher killifish abundances in upstream reaches. Our results, coupled with previous evidence of guppies altering killifish populations, suggest that the mediating effects of a third-party species (guppies) on predator–prey (killifish–caddisfly) interactions can affect the population size structure of prey populations.

The ornamental fish trade provides a pathway for the global translocation of aquatic parasites. We examined a total of 1020 fish imported from Singapore, Malaysia, Thailand, or Sri Lanka to Australia (including freshwater and marine fish species) for monogenean ectoparasites. Fish were received following veterinary certification that they showed no clinical signs of pests and diseases from the exporting country and visual inspection at Australian border control. Australian import conditions require mandatory treatment for goldfish with parasiticides (e.g. trichlorfon, formaldehyde, sodium chloride) for the presence of gill flukes (Dactylogyrus vastator Nybelin, 1924 and Dactylogyrus extensus Mueller and Van Cleave, 1932) prior to export. Over 950 individual parasites were detected in five imported fish species, representing 14 monogenean species. Seven Dactylogyrus spp. including D. vastator and three Gyrodactylus spp. infected goldfish, Carassius auratus Linnaeus, 1758, from Malaysia, Singapore, and Thailand. Dactylogyrus ostraviensis Řehulka, 1988, infected rosy barb, Pethia conchonius Hamilton, 1822, from Singapore, Sri Lanka, and Thailand while two Trianchoratus spp. infected three spot gourami, Trichopodus trichopterus Pallas, 1970 and pearl gourami Trichopodus leerii Bleeker, 1852, from Sri Lanka. Urocleidoides reticulatus Mizelle & Price, 1964, infected guppy, Poecilia reticulata Peters, 1859, from Sri Lanka. The discovery of D. vastator in goldfish, as well as 13 other monogenean species, shows that pre-export health requirements, which include chemical treatment of goldfish, and inspection of all ornamental fish species did not prevent infection by monogeneans. Inspection prior to exportation and at border control must account for the highly cryptic nature of monogenean parasites and consider alternatives to current pre-export conditions and visual inspection at border control.

To understand how the diversity among male sexual traits is maintained despite directional female choice for attractive traits, it is important to study male reproductive success in each reproductive episode. Male reproductive success is indeed the comprehensive result of several processes such as mate choice, mating, and fertilization. In this study, male mating success was estimated in a wild guppy Poecilia reticulata population of Hiji River, Okinawa Island, in southern Japan. The mating success of males was estimated as the percentage of sperm transferred in relation to the total sperm reserve. In a preliminary experiment, it was confirmed that the sperm reserves of males were partly replenished after 12 h and fully replenished after 72 h, when all sperm were released. In addition, the results of investigation in the wild population revealed that approximately 20% of males had no sperm reserves at all, although their sperm reserves should have been replenished by sexual isolation. Male sexual traits such as body size or color pattern did not affect the percentage of sperm transferred. Results from this study provide important insights into male sperm transfer ability and sperm production in this population. However, the high frequency of male sperm-transfer success estimated in this study should to be taken with caution, and whether it is due to differences between wild and laboratory conditions, sex ratio or the rates of multiple matings by females in the wild population remain to be fully explored.

Introduced alien fish species and their associated parasites may result in a serious threat to indigenous biodiversity. Furthermore, this may have negative impacts on cultured fish as well as on native parasitic fauna. In the present study, the invasive Asian nematode, Camallanus cotti Fujita, 1927 (Nematoda: Camallanidae), is reported from the guppy (Poecilia reticulata) for the first time in Africa. This parasite is assumed to be introduced into Africa along with the introduction of exotic poeciliid fishes, which are known to be the most common hosts of C. cotti in ornamental fish industry worldwide.The presence of this parasite in both aquarium-cultured fish as well as fish from natural waterbodies is evidence of the introduction of the alien organisms due to insufficient prophylactic veterinary control during transfer of non-native hosts between countries and the spread of them by the anthropogenic introduction to natural systems.

The present study was carried out to establish the biofabrication of palladium nanoparticles (PdNPs) using the plant leaf extract of Tinospora cordifolia Miers and its toxicity studies on the larvae of filariasis vector, Culex quinquefasciatus Say and malaria vector, Anopheles subpictus Grassi. The biofabricated PdNPs were characterized by using UV-visible spectrum, FTIR, XRD, FESEM, EDX and HRTEM. HRTEM confirmed the PdNPs were slightly agglomerated and spherical in shape and the average size was 16 nm. Gas chromatography and mass spectrometry analysis result revealed that the major constituent present in the T. cordifolia leaf extract is 2,4-di-tert-butylphenol (31.79%) whereas the minor compounds are 1-hexadecanol (7.97%), 1-octadecanol (7.70%), 1-eicosanol (6.85%), behenic alcohol (5.36%), 1-tetradecene (6.22%), cyclotetradecane (6.23%), 1-hexadecene (7.97%), 1-octadecene (7.70%), 1-eicosene (6.85%), and 1-docosene (5.36%). T. cordifolia leaf extract exhibited the larvicidal activity against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC50 = 59.857 and 54.536 mg/L; LC90 = 113.445 and 108.940 mg/L, respectively. The highest toxicity was observed in the biofabricated PdNPs against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC50 = 6.090 and 6.454 mg/L; LC90 = 13.689 and 13.849 mg/L, respectively. Concerning non-target effects, Poecilia reticulata were exposed to PdNPs for 24 h and did not exhibit any noticeable toxicity. Overall, our findings strongly suggest that PdNPs is a perfect ecological and inexpensive approach for the control of filariasis and malaria vectors.

Objective The purpose of this study was to segregate the genetic lines responsible for the orange area of coloration in males and the response to orange coloration exhibited by females in the guppy (Poecilia reticulata) through artificial selection. This study is part of a project that uses QTL-seq to search for candidate genes involved in male orange coloration and female response to male coloration. We created two lines: high-selected lines of males having large areas of orange spots and of females with high response to male orange coloration; and low-selected lines of males having small areas of orange spots and of females with low response to male orange coloration. Results The male orange area and the female response became significantly different between high- and low-selected lines after three generations of artificial selection. This indicates that the differences in the frequencies of alleles at loci affecting the orange area and the female response between the lines increased over the generations through selection.

Our understanding of nanoparticle toxicity and fate in the aquatic environment is still patchy. In the present study, the toxicity of silver nanoparticles coated by Camellia sinensis (Cs) leaf extract metabolites (Cs-AgNPs) was investigated in comparison with C. sinensis leaf extract and AgNO3 on a micro-crustacean, Ceriodaphnia cornuta, and a fish Poecilia reticulata. 100% mortality of C. cornuta was observed post-exposure to AgNO3 (40 µg/ml) if compared to the Cs leaf extract and Cs-AgNPs, showing 30 and 56% mortality at the same concentration, respectively. In P. reticulata 100% mortality was observed testing AgNO3 and Cs-AgNPs post-exposure to 1 and 30 µg/ml, respectively. Light microscopy and CLSM images showed the accumulation of nanoparticles in the intestine of C. cornuta treated with Cs-AgNPs at 40 µg/ml. In addition, histological observations confirmed the abnormal tissue texture in nanoparticle-exposed P. reticulata, if compared to control fishes. Furthermore, C. cornuta and P. reticulata treated with Cs-AgNPs showed DNA damages compared to the control. Overall, these findings indicated relevant limits about the employ of silver-based pesticides in the environment, and also pointed out the Cs-AgNPs were less toxic to C. cornuta and P. reticulata if compared to silver ions.

Recently, the green synthesis of silver nanoparticles gained increasing attention due to interesting properties for optical, antimicrobial and pest control applications. However, their toxicity against micro-crustaceans and fishes has been scarcely explored, while most of the research efforts focused on mosquito control with the green-synthesized nanocomposites. In this study, we investigated the toxic effects of AgNO3, Cissus quadrangularis (Cq)-synthesized AgNPs and Cq extract in two different study models, the larvae of Poecilia reticulata fishes and adults of the micro-crustacean Ceriodaphnia cornuta. In both species, AgNO3 and Cq-AgNPs showed high mortality rates even if tested at very low doses. Molecular analysis revealed high DNA damages induced by Cq-AgNPs on both aquatic organisms. Furthermore, light microscopy studies evidenced lesions in the gills and vacuolization in the gills and in the abdomen of P. reticulata larvae. Overall, our research pointed out that the exposure of aquatic organisms to AgNO3 or green-fabricated AgNPs can damage fishes and crustaceans, posing noteworthy risks to the aquatic ecosystems.

The shoal-choice test is a popular method to investigate quantity discrimination in social fish based on their spontaneous preference for the larger of two shoals. The shoal-choice test usually requires a long observation time (20-30 min), mainly because fish switch between the two shoals with low frequency, thus reducing the possibilities of comparison. This duration limits the use of the shoal-choice test for large-scale screenings. Here, we developed a new version of the shoal-choice test in which the subject was confined in a large transparent cylinder in the middle of the tank throughout the experiment to bound the minimum distance from the stimulus shoals and favour switching. We tested the new method by observing guppies (Poecilia reticulata) in a 4 versus 6 fish discrimination (experiment 1). The new method allowed for a faster assessment of the preference for the larger shoal (

A recent study found that guppies (Poecilia reticulata) can be trained to discriminate 4 versus 5 objects, a numerical discrimination typically achieved only by some mammals and birds. In that study, guppies were required to discriminate between two patches of small objects on the bottom of the tank that they could remove to find a food reward. It is not clear whether this species possesses exceptional numerical accuracy compared with the other ectothermic vertebrates or whether its remarkable performance was due to a specific predisposition to discriminate between differences in the quality of patches while foraging. To disentangle these possibilities, we trained guppies to the same numerical discriminations with a more conventional two-choice discrimination task. Stimuli were sets of dots presented on a computer screen, and the subjects received a food reward upon approaching the set with the larger numerosity. Though the cognitive problem was identical in the two experiments, the change in the experimental setting led to a much poorer performance as most fish failed even the 2 versus 3 discrimination. In four additional experiments, we varied the duration of the decision time, the type of stimuli, the length of training, and whether correction was allowed in order to identify the factors responsible for the difference. None of these parameters succeeded in increasing the performance to the level of the previous study, although the group trained with three-dimensional stimuli learned the easiest numerical task. We suggest that the different results with the two experimental settings might be due to constraints on learning and that guppies might be prepared to accurately estimate patch quality during foraging but not to learn an abstract stimulus-reward association.

Individual differences in lateralization of cognitive functions characterize both humans and non-human species. Genetic factors can account for only a fraction of the variance observed and the source of individual variation in laterality remains in large part elusive. Various environmental factors have been suggested to modulate the development of lateralization, including asymmetrical stimulation of the sensory system during ontogeny. In this study, we raised newborn guppies in an asymmetric environment to test the hypothesis that early left-right asymmetries in visual input may affect the development of cerebral asymmetries. Each fish was raised in an impoverished environment but could voluntarily observe a complex scene in a nearby compartment containing a group of conspecifics. Using asymmetric structures, we allowed some subjects to observe the complex scene with the right eye, others with the left eye, and control fish with both eyes. Among asymmetrically stimulated fish, the mirror test revealed eye dominance congruent with the direction of asymmetric stimulation, while controls showed no left-right laterality bias. Interestingly, asymmetric exposure to social stimuli also affected another aspect of visual lateralization-eye preference for scrutinizing a potential predator-but did not influence a measure of motor asymmetry. As the natural environment of guppies is fundamentally asymmetrical, we suggest that unequal left-right stimulation is a common occurrence in developing guppies and may represent a primary source of individual variation in lateralization as well as an efficient mechanism for producing laterality phenotypes that are adapted to local environmental conditions.

Exploratory behavior—an individual’s response to novel environments, resources, or objects—should vary with the associated benefits, including new sources of food and reduced levels of competition, and the costs, such as predation pressure. Using guppies from multiple streams and rivers in Trinidad, we compared guppies from high- and low-predation populations. We found that wild-caught male and female guppies from low-predation populations were more exploratory than high-predation fish when tested in the field and in controlled laboratory conditions. We did not detect significant evidence for a genetic basis for differences in the behavior of high- and low-predation fish using a common-garden approach, but further study is required before conclusions can be made about the relative contribution of genes to population differences in exploratory behavior of guppies. Theory has assumed that predation risk is a cost that will select against high levels of exploratory behavior; this study is one of the few that has tested this assumption, and we show that exploratory behavior is indeed suppressed in guppies from high-predation localities. Exploratory behavior is a component of an individual’s responses to novel environments, resources, and objects (including potential predators) and thus can affect important decisions of animals in the wild (e.g., whether to sample new, potential sources of food, whether to disperse). We compared exploratory behavior of wild-caught guppies from sites with large, dangerous predators with those from sites with small predators that are only a threat to small individuals. Guppies co-occurring with large predators were less exploratory than those from sites with small predators. Factors contributing to this difference could include exposure to predators directly and to conspecifics’ responses to predators. Studies on general behavioral traits (e.g., temperament) combined with knowledge of animals’ environment and evolution are expanding our ability to test ideas about the origin and maintenance of intra-specific variation in fascinating and complex traits.

Selection pressure from parasites is thought to be a major force shaping the extreme polymorphism of the major histocompatibility complex (MHC) genes, but the modes and consequences of selection remain unclear. Here, we analyse MHC class II and microsatellite diversity in 16 guppy (Poecilia reticulata) populations from two islands (Trinidad and Tobago) that have been separated for at least 10 ky. Within-population MHC diversity was high, but allele sharing was limited within islands and even lower between islands, suggesting relatively fast turnover of alleles. Allelic lineages strongly supported in phylogenetic analyses tended to be island-specific, suggesting rapid lineage sorting, and an expansion of an allelic lineage private to Tobago was observed. New alleles appear to be generated locally at a detectably high frequency. We did not detect a consistent signature of local adaptation, but F

Animals can adapt to changes in their environment through behavioural or developmental plasticity, but studies of these responses tend to focus on either short-term exposure of adults to the changed conditions, or long-term exposure of juveniles. Juvenile guppies Poecilia reticulata reared in low-light environments have previously been shown to make a sensory switch to using olfactory, rather than visual, cues in foraging. It is not clear whether this compensatory sensory plasticity is limited to juveniles, or whether longer term exposure allows adults to similarly adapt. We investigated how adult guppies that were exposed to light or dark environments for 2 and 4 weeks responded to visual, olfactory and a combination of both food cues, in both dark- and light-test environments. We found that after 2 weeks of exposure, adult guppies were better able to locate a food cue in light test environments regardless of their exposure environment. After 4 weeks, however, guppies were more successful at locating the food cue in the environment they had been exposed to, suggesting that dark-exposed guppies adapted their behaviour in response to their environment. We found that foraging was most successful when both visual and olfactory cues were available and least successful in the presence of olfactory cues, suggesting that the mechanism behind the change in success for dark-exposed guppies was not due to increased reliance on, or sensory switch to olfactory cues. Human-induced environmental change often acts to disrupt an animal’s sensory environment. For example, turbidity can degrade the visual environment, resulting in reduced foraging rates in fish. Juvenile guppies (Poecilia reticulata) can compensate for the reduced visual information available in low-light environments through developmental changes that allow them to rely on an alternative sense, olfaction. This ability, however, may be limited to a critical developmental window, or possible throughout life. Here, we show that while adult guppies are generally better able to locate food resources in well-lit environments, after four (but not two) weeks living under low-light conditions, fish were better able to find food in dark environments than in the light. However, unlike juvenile fish, they did not seem to be relying more on olfactory cues to do so.

Establishing behavioural repeatability is important in animal personality research; however, a range of factors can influence repeatability. Experimental design, particularly acclimation time, is important in managing a subject’s stress prior to the onset of behavioural observations. Acclimatisation also ensures we capture “normal” behaviour and promotes consistency in the subject’s responses between observations. The importance of acclimatisation prior to an assay is widely recognised by animal researchers; however, acclimation time varies dramatically across personality studies. Here, we investigated the effects of acclimatisation time on the repeatability of activity and emergence behaviour in feral and domestic populations of lab-reared guppy, Poecilia reticulata. Contrary with expectations and previous findings, we found highest repeatability in guppy activity levels after 2 h of acclimation to the test arena. In the emergence assay, fish exposed to 10 min of acclimatisation showed highest repeatability; however, all acclimation periods produced high repeatability, suggesting that the emergence assay generates robust behavioural responses irrespective of acclimation time. The outcomes were broadly consistent across both populations. These results show that methodology can impact the findings of animal personality research and needs to be considered carefully for each assay. We recommend that researchers investigate appropriate acclimatisation times for their study species prior to commencing research. Animal personality is individual differences in behaviour that are maintained through time and across contexts. Thus, demonstrating the repeatability of behavioural differences between individuals is imperative to establishing animal personality. To estimate repeatability, individuals are assessed multiple times on the same task to ensure there are consistent differences between individuals. When carrying out repeated observations, acclimatisation time should be considered to minimise stress levels of an animal prior to the behavioural assay. We assessed a range of acclimation times on emergence and activity behaviour in two populations of guppies. While individual variation in emergence behaviour was repeatable across a range of acclimation times, activity levels in guppies became significantly more repeatable after 2 h of acclimatisation. These results show that considering proper acclimation time is important when performing behavioural experiments and should be properly calibrated by researchers prior to conducting personality research.

Artificial light at night (ALAN) is a major form of anthropogenic pollution. ALAN is well known to affect different behaviours during nighttime, when changes in light conditions often have immediate consequences for the trade-offs individuals experience. How ALAN affects daytime behaviours, however, has received far less attention. Here we studied how ALAN affected daytime personality traits and learning ability. We exposed Trinidadian guppies, Poecilia reticulata, for 10 weeks to different ALAN levels: bright light (24 hrs bright light, ~5,000 lx), dim light (12 hrs bright light; 12 hrs dim light, ~0.5 lx) and control (12 hrs bright light; 12 hrs dark). Afterwards, we tested how the treatments affected diurnal emergence from a refuge, space use, activity, sociability and the ability to memorize the location of companion fish. Individuals exposed to the light treatments (both dim and bright light) emerged quicker from a refuge and fish from the bright light treatment spent relatively more time in the open area of the arena. ALAN did not affect any of the other behaviours, although memory could not be tested since fish did not learn the companions’ location. Our results demonstrate that ALAN, next to affecting nocturnal behaviours, can also affect key diurnal behavioural processes, associated with risk-taking.

Phenotypic variation plays a critical role in determining the structural organisation and ecological function of wild populations. Animal groups are often structured according to factors such as species, sex, body size and parasite load, but it is unclear whether body shape also influences patterns of social organisation, and thus contributes to population phenotypic structure. Here, we use geometric morphometric analyses to determine whether wild-caught shoals of a freshwater fish, the western rainbowfish (Melanotaenia australis), are structured according to body size and shape. Using randomisation analyses, we show that the level of variation in size and shape observed in natural group assemblages is lower than that expected under a null model of random shoal composition. In addition, we found evidence of further phenotypic structuring along an upstream-downstream environmental gradient. The putative benefits of morphological assortment include a reduction in predation risk (due to prey oddity and predator confusion effects) and increased hydrodynamic or foraging efficiency. We suggest that morphological variation is a neglected component of population social organisation that can affect population processes, such as patterns of gene flow, and ecological interactions, such as predator-prey dynamics.

Ectotherms depend on the environmental temperature for thermoregulation and exploit thermal regimes that optimise physiological functioning. They may also frequent warmer conditions to up-regulate their immune response against parasite infection and/or impede parasite development. This adaptive response, known as ‘behavioural fever’, has been documented in various taxa including insects, reptiles and fish, but only in response to endoparasite infections. Here, a choice chamber experiment was used to investigate the thermal preferences of a tropical freshwater fish, the Trinidadian guppy (Poecilia reticulata), when infected with a common helminth ectoparasite Gyrodactylus turnbulli, in female-only and mixed-sex shoals. The temperature tolerance of G. turnbulli was also investigated by monitoring parasite population trajectories on guppies maintained at a continuous 18, 24 or 32 °C. Regardless of shoal composition, infected fish frequented the 32 °C choice chamber more often than when uninfected, significantly increasing their mean temperature preference. Parasites maintained continuously at 32 °C decreased to extinction within 3 days, whereas mean parasite abundance increased on hosts incubated at 18 and 24 °C. We show for the first time that gyrodactylid-infected fish have a preference for warmer waters and speculate that sick fish exploit the upper thermal tolerances of their parasites to self medicate.

In the presence of predators, many prey species exhibit immediate behavioral responses like the avoidance of risky areas, which imposes opportunity costs, for instance, in the form of reduced foraging. Thus, prey species should be able to discriminate between different predator types and adjust their response to the imminent predation risk. In our current study, we evaluated the relative importance of innate versus learned components of predator recognition and avoidance in the guppy (Poecilia reticulata). We used a feral guppy population occurring in Germany and compared avoidance reactions of each focal individual towards both coevolved piscine predators from their original distribution range and novel, presently co-occurring predator species. Wild-caught, predator-experienced as well as laboratory-reared, predator-naive individuals showed strong avoidance responses towards all predator animations. Avoidance was stronger in small-bodied than in large-bodied individuals in both cohorts; however, this effect was significant only in predator-naive fish. Moreover, wild-caught individuals showed a significantly higher within-individual variance (across the six predator species) along with a lower among-individual variance in predator avoidance, which resulted in a lower behavioral repeatability in this cohort. Our results suggest that consistent individual differences in risk-taking behavior (also referred to as the personality trait ‘boldness’) are modified by predator exposure and learning about predators.

Pregnancy inhibits locomotion, increases predation risk and may translate into reduced survival. The extent to which animals modify behavior in the wild to compensate for the locomotor costs of pregnancy remains poorly understood. We have investigated how reproductive allocation (RA-the proportion of body mass devoted to reproduction) affects locomotor performance and habitat use in Trinidadian guppy (Poecilia reticulata) populations from low- and high-predation regimes. During steady swimming, females with high RA had increased tail beat amplitudes, indicating increased swimming costs. Females with high RA also exhibited slower escape velocities, which may result in an increased risk of predation. In low-predation localities, females with high RA used habitats with a lower water velocity, suggesting that females may be modifying behavior to offset the locomotor costs of pregnancy. Habitat use in high-predation localities was severely restricted to areas without predators, which had a relatively slower water velocity with little or no variation in current. These results provide a link between the performance-related costs of reproduction and behavior in a natural setting and show that animals may compensate for reproductive traits that constrain locomotor performance by modifying habitat use.

Aquarium trade has been recognized as one of the major pathways of introduction of non-native fishes into new regions. Nearly 43 million freshwater ornamental fish of different species and varieties are annually commercialized in Mexico and there is a high probability for the establishment of some of these species because of their invasive attributes and the diverse climatic zones existing in the country. Within this context, the identification of high-risk species is of paramount importance considering the potential threat to Mexico’s great biological diversity. In the present study 700 freshwater aquarium fish species commonly imported and produced in the country were filtered for synonyms/varieties, resulting in 368 species, which where submitted to revision for invasive reports using specialized invasive species databases. This allowed ranking the main invasive species and the top 30 were subjected to risk analysis using the Fish Invasiveness Screening Kit (FISK). Calibration of FISK was carried out after generating the reports. A receiver operating characteristic curve was made to determine the FISK ability to discriminate between invasive and non-invasive species in Mexico. Thereafter, Youden’s index was calculated and a threshold of 24 was obtained, representing the cut-off value for defining high-risk species. A total of 17 species out of 30 were classified under a high-risk category, among them several species of the genus Xiphophorus, Pterygoplichthys and Poecilia. Most of the species were native to Asia, Central and South America. Some of these species are already invasive in Mexico.

Phenotypic plasticity is the capacity for an individual genotype to produce different phenotypes in response to environmental variation. Most traits are plastic, but the degree to which plasticity is adaptive or non-adaptive depends on whether environmentally induced phenotypes are closer or further away from the local optimum. Existing theories make conflicting predictions about whether plasticity constrains or facilitates adaptive evolution. Debate persists because few empirical studies have tested the relationship between initial plasticity and subsequent adaptive evolution in natural populations. Here we show that the direction of plasticity in gene expression is generally opposite to the direction of adaptive evolution. We experimentally transplanted Trinidadian guppies (Poecilia reticulata) adapted to living with cichlid predators to cichlid-free streams, and tested for evolutionary divergence in brain gene expression patterns after three to four generations. We find 135 transcripts that evolved parallel changes in expression within the replicated introduction populations. These changes are in the same direction exhibited in a native cichlid-free population, suggesting rapid adaptive evolution. We find 89% of these transcripts exhibited non-adaptive plastic changes in expression when the source population was reared in the absence of predators, as they are in the opposite direction to the evolved changes. By contrast, the remaining transcripts exhibiting adaptive plasticity show reduced population divergence. Furthermore, the most plastic transcripts in the source population evolved reduced plasticity in the introduction populations, suggesting strong selection against non-adaptive plasticity. These results support models predicting that adaptive plasticity constrains evolution, whereas non-adaptive plasticity potentiates evolution by increasing the strength of directional selection. The role of non-adaptive plasticity in evolution has received relatively little attention; however, our results suggest that it may be an important mechanism that predicts evolutionary responses to new environments.

Foraging theory predicts which prey patches predators should target. However, in most habitats, what constitutes a 'patch' and how prey density is calculated are subjective concepts and depend on the spatial scale at which the predator (or scientist) is observing. Moreover, the predator's 'foraging scale' affects prey population dynamics: predators should produce directly density-dependent (DDD) prey mortality at the foraging scale, but inversely density-dependent (IDD) mortality (safety-in-numbers) at smaller scales. We performed the first experimental test of these predictions using behavioral assays with guppies (Poecilia reticulata) feeding on bloodworm 'prey' patches. The guppy's foraging scale had already been estimated in a prior study. Our experimental results confirmed theoretical predictions: predation was IDD when prey were aggregated at a scale smaller than the foraging scale, but not when prey were aggregated at larger scales. These results could be used to predict outcomes of predator-prey interactions in continuous, non-discrete habitats in the field.

In recent years, the use of operant conditioning procedures has shown that species as diverse as chimpanzees, honeybees, and mosquitofish can be trained to discriminate between sets containing different numbers of objects. However, to succeed in this task, subjects can use two different strategies: either select the array containing a specific number of items (an absolute numerosity rule), or select the set containing the larger (or smaller) quantity of items (a relative numerosity rule). In the latter case, subjects need not only be able to judge whether two numerosities are equal or different but also be able to order numerosities. Here, in two experiments, we address whether fish can perform both kinds of judgment by training them with specific numerosities and testing their generalization to new numerosity contrasts. In Experiment 1, subjects were initially trained to select between visual arrays of 6 and 12 shapes, and were then tested with a contrast pairing the previously trained numerosity (either 6 or 12) with a novel numerosity (respectively, 3 or 24). Spontaneously, subjects selected the novel numerosity, in accordance with a relative numerosity rule. The second experiment tested whether guppies can also learn to select one specific number against all others, if appropriately trained. Fish trained to select an array of 4 shapes against several alternatives (4 vs. 1, 4 vs. 2, 4 vs. 8, 4 vs. 10) learned to recognize the number 4 against all alternatives and proved able to generalize their discrimination to novel, more difficult contrasts (4 vs. 3 and 4 vs. 6 items). In summary, although guppies preferentially opt for relative comparisons, they can flexibly learn either relative or absolute decision criteria on numerosity stimuli, depending on the context.

Turbidity (a measure of the cloudiness of water) decreases the visual range of organisms, altering interactions within and between species. For species that visually assess mates, turbidity may affect mating interactions and mate choice. A central question, then, is to what degree organisms plastically adjust mating behaviors to cope with visually altered environments. Here, we investigate the effect of turbidity on the mating behavior of guppies (Poecilia reticulata) in Trinidad, where some streams are increasingly turbid due to upstream rock quarrying. We collected fish from two highly turbid streams (with upstream rock quarries) and two pristine streams (no upstream quarries) in the same drainages. We then observed male mating behaviors with females from the same populations in both turbid and clear assays, recording displays and sneak copulation attempts. Males from turbid streams showed greater individual consistency in mating behaviors. But regardless of provenance, male guppies spent less time associating with females in turbid water overall. When males and females did interact, however, males greatly increased the rate of all mating behaviors in turbid as compared to clear water. Thus, even when lacking a long-term evolutionary history with high turbidity, guppies compensate for lost time when mating in a visually altered environment. Given the global nature of increases in turbidity, understanding behavioral responses to this aquatic anthropogenic change is critical. Here, we investigate the degree to which Trinidadian guppy males in affected areas are able to plastically compensate in turbid water by adjusting mating behaviors. We also test the degree to which previous chronic exposure to turbidity alters this plasticity. In contrast to predictions, we did not find population differences in plasticity; across all populations, however, we found significant plasticity in the guppy mating system in response to anthropogenically increased turbidity. While males spent less time associating with females in turbid water overall, males increased mating effort during periods of association, compensating for lost time in turbid water. We discuss this plasticity and the implications for guppy sexual selection and secondary sexual characteristics such as coloration.

Animals may use public information gained by observing sexual interactions between conspecifics and use this information for their own mate choice. This strategy, called mate-choice copying, is considered to play an important role for the evolution of mate preferences. Mate-choice copying is defined as non-independent mate choice, in which a female’s probability of choosing a given male increases if other females have chosen that male previously. Using the livebearing sailfin molly (Poecilia latipinna), we asked if increasing the distance between a model female and a male would affect copying behaviour of focal females. We tested focal females in two different treatments: (1) model female and male in close proximity and able to interact at close range and (2) model female and male positioned apart from each other and restricted from close-range interactions. We could show that focal females copied the choice of a model at short distance to the prior non-preferred male as predicted from previous experiments. Surprisingly, focal females also copied the choice of a model when positioned 40 cm apart from the male. When no model female and, hence, no public information were provided (choice consistency control), focal females were consistent in their mate choice, indicating that changes in mate preference observed in the two treatments were due to the simulated mate choice of the model female. Our results demonstrate that females gain and use public information and copy the mate choice of other females even when heterosexual conspecifics interact from a distance. Animals can copy the mate choice of conspecifics by observing their sexual interactions and, hence, choose the same mate as the other individual did before. So far, mate-choice copying was investigated when the so-called model female and the male were in close proximity. Here, we investigated whether female sailfin mollies (Poecilia latipinna) copy the choice of a model female for a male when the model female can only interact with a male at distance. We show for the first time that even interactions of heterosexual conspecifics at distance provide public information for an observing focal female to copy the choice of the model. Our results imply an even wider information transfer in sailfin molly social networks than previously thought.

Recent studies have shown that prey living under conditions of elevated predation risk respond very differently to novel predators than prey living under low-risk conditions, by displaying generalized avoidance patterns to novel stimuli. This phenotypic plasticity in neophobic responses provides prey with the means to respond flexibly to uncertain risks, but we know almost nothing about how long neophobic responses are maintained. Using extinction testing, we demonstrate that neophobic responses of guppies (Poecilia reticulata) to a novel odour waned relatively quickly over five consecutive exposures, but the waning of responses to one stimulus does not affect neophobic responses to other novel odours. In a subsequent experiment, we demonstrate that learned responses to predator cues in fish from high- and low-risk populations both waned over time, but fish from the high-risk population retained the response longer than those from the low-risk population. Background levels of predation risk appear to be crucial factors in driving differences in retention of risk-related information.

Turbidity, caused by suspended particles in the water column, induces light scattering and shifts in the wavelengths of light. These changes may impair the ability of fish to use physical cues and hence may modify social interactions. We experimentally investigated the social interactions of guppies, Poecilia reticulata, in clear and turbid water. Fish were significantly less active, formed smaller shoals and were found to be more often alone in turbid than in clear water. A Markov chain analysis revealed significant differences in the social dynamics when comparing clear and turbid water conditions. The probability of leaving a particular nearest neighbour and the probability of choosing some neighbour after swimming around alone differed between the treatments. Our results indicate that turbidity has a number of different effects on the social interactions of the guppy, and we discuss their potential costs and benefits and wider implications.

Urbanization can impact coastal fisheries by reducing the quality of important habitats, including salt marshes. Similarly, increased urban land use surrounding tidal creeks can impact the health of fish by changing salinities, altering habitat structure, and increasing exposure to pollution. In this study, we investigated the effects of residential urban land use on the condition of salt marsh resident fish along the northern Gulf of Mexico. Fish were sampled seasonally using minnow traps along salt marshes near the mouth of six second-order tidal creeks (three surrounded by residential development and three surrounded primarily by forest) in Alabama and west Florida. Fundulus grandis and Poecilia latipinna were the dominant species representing 65 % (n = 3588) and 15 % (n = 777) of the total number of fish caught, respectively. All F. grandis and P. latipinna were evaluated for mass, length, and length-weight relationship. A subset (745 and 367, respectively) was further analyzed for conditional measures of caloric density and liver somatic index (LSI). The mass per length relationships did not differ between urban and reference creeks for either F. grandis or P. latipinna; however, reference creeks yielded F. grandis and P. latipinna that were significantly larger. Further, F. grandis and P. latipinna had significantly lower LSI and caloric density in urban creeks compared to reference. Both species showed seasonal patterns of conditional measures that were likely related to reproduction and annual fattening cycles. Differences in fish condition between urban and reference creeks may reflect differences in food availability/quality, creek salinity regimes, and salt marsh structure.

Based on the nutrient requirement of guppy, Poecilia reticulata fingerlings as reported earlier, nine experimental diets with 300 g protein, 100 g lipid and 16.72 MJ digestible energy/kg diet were formulated using snail meat (D-1), freshwater fish processing waste (D-2), surimi by-product (D-3), chicken offal (D-4), earthworm (D-5), squid (D-6), mussel (T-7), chicken liver (T-8) and lean prawn (T-9) as major protein source in addition to fish meal and peanut oil cake and fed ad libitum to the fish (0.27 ± 0.01 g) for a period of 60 days. Twenty-seven indoor circular fiber-reinforced plastic tanks (10 fish/tank) with 40 L of water were used for rearing the fish. At the end of the experiment, it was found that the guppy fed surumi by-product, squid, mussel and lean prawn meal diets had significantly higher (p < 0.05) weight gain, specific growth rate and protein efficiency ratio and lowest (p < 0.05) food conversion ratio than the snail, freshwater fish processing waste, chicken offal, earthworm and chicken liver meal diets and therefore, these four could be used as dietary protein source in formulating the diets for guppy. However, to formulate the cost-effective diets for guppy fingerlings, the use surimi by-product is suggested as it is being discarded as waste material and therefore, available free of cost.

The movement of animals in groups is widespread in nature. Understanding this phenomenon presents an important problem in ecology with many applications that range from conservation to robotics. Underlying all group movements are interactions between individual animals and it is therefore crucial to understand the mechanisms of this social behaviour. To date, despite promising methodological developments, there are few applications to data of practical statistical techniques that inferentially investigate the extent and nature of social interactions in group movement. We address this gap by demonstrating the usefulness of a Hidden Markov Model approach to characterise individual-level social movement in published trajectory data on three-spined stickleback shoals (Gasterosteus aculeatus) and novel data on guppy shoals (Poecilia reticulata). With these models, we formally test for speed-mediated social interactions and verify that they are present. We further characterise this inferred social behaviour and find that despite the substantial shoal-level differences in movement dynamics between species, it is qualitatively similar in guppies and sticklebacks. It is intermittent, occurring in varying numbers of individuals at different time points. The speeds of interacting fish follow a bimodal distribution, indicating that they are either stationary or move at a preferred mean speed, and social fish with more social neighbours move at higher speeds, on average. Our findings and methodology present steps towards characterising social behaviour in animal groups. Electronic supplementary material The online version of this article (10.1007/s00114-017-1534-9) contains supplementary material, which is available to authorized users.

Guppy (Poecilia reticulata) is an ideal model for studying environmental estrogens, and its large caudal fin has a high capacity to regenerate. This study analyzed the feasibility of caudal fin for detecting vitellogenin (Vtg), the most commonly used biomarker of environmental estrogens. Firstly, a sandwich ELISA for guppy Vtg was developed using purified lipovitellin and its antibody and it had a working range of 7.8–1000 ng/mL and detection limit of 3.1 ng/mL. The ELISA was used to detect tissue distribution of Vtg. In male guppy exposed to 50 and 100 ng/L 17β-estradiol (E2), Vtg concentration in caudal fin was higher than that in whole fish, brain, eyes, gonad, and skin, and was close to that in the liver. Furthermore, male guppies were exposed to environmental concentrations of 17a-ethinylestradiol (EE2) and bisphenol S (BPS) to validate the utility of caudal fin Vtg for detecting estrogenic activities. The lowest observed effect concentration of EE2 and BPS were lower than 2 ng/L and 1 μg/L, which were below or equal to the values reported for other species, demonstrating that caudal fin Vtg was highly sensitive to estrogenic chemicals. Therefore, caudal fins of guppies are suggested as alternative samples for Vtg biomarker detection.