Freshwater Fish Poecilia Research Articles

Ecotoxicity of the formulated biosurfactant from Pseudomonas cepacia CCT 6659 and application in the bioremediation of terrestrial and aquatic environments impacted by oil spills

Dispersants with a low environmental impact are necessary for oil spill remediation. Thus, the biosurfactant produced by the bacterium Pseudomonas cepacia CCT6659 using industrial waste and formulated using a method of adding food preservative was evaluated for its toxicity against the vegetable Allium cepa and aquatic species such as the freshwater fish Poecilia vivipara and the bivalve Anomalocardia brasiliana. The biosurfactant was also applied in the removal of hydrophobic contaminant in sand and soils, in sea stones, in the dispersion and in the bioremediation of oil in seawater. The surfactant was considered to be of low toxicity for the bioindicators evaluated. As a petroderivative removal agent, the formulated tensoactive reached 76.55 % removal in soil and 84.50 % in sea stones. The biosurfactant was able to disperse 96.00 % of oil in seawater and promoted an increase in the biodegradation of oil by 70.00 % during a bioremediation process carried out in seawater. Therefore, the formulated biosurfactant presents suitable conditions for application as a dispersing agent in the decontamination of terrestrial and aquatic environments impacted by oil spills in substitution of chemical and toxic compounds.

Extreme Y chromosome polymorphism corresponds to five male reproductive morphs of a freshwater fish.

Loss of recombination between sex chromosomes often depletes Y chromosomes of functional content and genetic variation, which might limit their potential to generate adaptive diversity. Males of the freshwater fish Poecilia parae occur as one of five discrete morphs, all of which shoal together in natural populations where morph frequency has been stable for over 50 years. Each morph uses a different complex reproductive strategy and morphs differ dramatically in colour, body size and mating behaviour. Morph phenotype is passed perfectly from father to son, indicating there are five Y haplotypes segregating in the species, which encode the complex male morph characteristics. Here, we examine Y diversity in natural populations of P. parae. Using linked-read sequencing on multiple P. parae females and males of all five morphs, we find that the genetic architecture of the male morphs evolved on the Y chromosome after recombination suppression had occurred with the X. Comparing Y chromosomes between each of the morphs, we show that, although the Ys of the three minor morphs that differ in colour are highly similar, there are substantial amounts of unique genetic material and divergence between the Ys of the three major morphs that differ in reproductive strategy, body size and mating behaviour. Altogether, our results suggest that the Y chromosome is able to overcome the constraints of recombination loss to generate extreme diversity, resulting in five discrete Y chromosomes that control complex reproductive strategies.

Y chromosome evolution spurs behavioural diversity in male fish.

The Y chromosome of the freshwater fish Poecilia parae may have successively evolved five haplotypes that are maintained in the population for alternative male reproductive strategies.

Environmentally relevant concentrations of benzophenone-3 induce differential histopathological responses in gills and liver of freshwater fish.

BP-3 is one of the most used organic UV filters. However, its widespread use and release into aquatic environment can induce ecotoxicological impact on aquatic organisms. Thus, the aim of the current study is to evaluate the gills and liver of freshwater fish Poecilia reticulata subjected to acute exposure (96 h) to BP-3 at environmentally relevant concentrations (10-1000 ng L-1). The study was based on adopting qualitative and semi-quantitative approach to assess histopathological changes and integrated the biomarker response in order to investigate organ-specific responses to BP-3 exposure. BP-3 has induced high histopathological index associated with circulatory disturbances, as well as with regressive and immunological changes in gills, whereas the hepatic histopathological index was associated with circulatory disturbances. Moreover, lower BP-3 concentrations were mostly associated with changes in gills, whereas higher BP-3 concentration was mostly linked to hepatic changes. In conclusion, acute exposure to BP-3 at environmentally relevant concentrations had stronger impact on gills than on the liver of P. reticulata, which confirmed organ-specific responses to UV filters.

Sulphide-toxic habitats are not refuges from parasite infections in an extremophile fish

We still have a limited understanding of why animals colonize extreme environments, but one hypothesis (the Pathogen Refuge Hypothesis, PRH) posits that they might represent a safe haven from parasites and other pathogens. We tested this idea by quantifying endoparasite infections in five populations of the neotropical freshwater fish Poecilia mexicana, three populations from toxic, H2S-rich habitats and two control populations from nearby rivers and creeks. Counter to predictions derived from the PRH, only P. mexicana from toxic habitats harboured heterophyid metacercariae in their hearts. We further uncovered differences in parasite prevalences and abundances between the three toxic habitats. Our results provide evidence against the PRH and add depth to our understanding of life in (and adaptation to) extreme environments.

Potential of fascaplysin and palauolide from Fascaplysinopsis cf reticulata to reduce the risk of bacterial infection in fish farming

Marine natural products isolated from the sponge Fascaplysinopsis cf reticulata, in French Polynesia, were investigated as an alternative to antibiotics to control pathogens in aquaculture. The overuse of antibiotics in aquaculture is largely considered to be an environmental pollution, because it supports the transfer of antibiotic resistance genes within the aquatic environment. One environmentally friendly alternative to antibiotics is the use of quorum sensing inhibitors (QSIs). Quorum sensing (QS) is a regulatory mechanism in bacteria which control virulence factors through the secretion of autoinducers (AIs), such as acyl-homoserine lactone (AHL) in gram-negative bacteria. Vibrio harveyi QS is controlled through three parallel pathways: HAI-1, AI-2, and CAI-1. Bioassay-guided purification of F. cf reticulata extract was conducted on two bacterial species, i.e., Tenacibaculum maritimum and V. harveyi for antibiotic and QS inhibition bioactivities. Toxicity bioassay of fractions was also evaluated on the freshwater fish Poecilia reticulata and the marine fish Acanthurus triostegus. Cyclohexanic and dichloromethane fractions of F. cf reticulata exhibited QS inhibition on V. harveyi and antibiotic bioactivities on V. harveyi and T. maritimum, respectively. Palauolide (1) and fascaplysin (2) were purified as major molecules from the cyclohexanic and dichloromethane fractions, respectively. Palauolide inhibited QS of V. harveyi through HAI-1 QS pathway at 50 μg ml–1 (26 μM), while fascaplysin affected the bacterial growth of V. harveyi (50 μg ml–1) and T. maritimum (0.25 μg). The toxicity of fascaplysin-enriched fraction (FEF) was evaluated and exhibited a toxic effect against fish at 50 μg ml–1. This study demonstrated for the first time the QSI potential of palauolide (1). Future research may assess the toxicity of both the cyclohexanic fraction of the sponge and palauolide (1) on fish, to confirm their potential as alternative to antibiotics in fish farming.

Emerging human pathogen Acinetobacter baumannii in the natural aquatic environment: a public health risk?

Bacterium Acinetobacter baumannii is an emerging human pathogen whose presence in the aquatic environment raises the issue of public health risk. Fish colonization represents the potential route of pathogen transmission to humans. The aim was to examine the colonization of A. baumannii to freshwater fish Poecilia reticulata. An extensively drug-resistant A. baumannii was tested at three concentrations in natural spring water. Additionally, 70 fish from the Sava River (Croatia) were screened for the presence of A. baumannii, which was not found in gill swabs or analysed gut. The colonization potential of A. baumannii in freshwater fish is dependent upon its concentration in surrounding water. The low concentration of A. baumannii in natural waters represents low colonization potential of freshwater fish. The risk for public health exists in closed water bodies where there is constant inflow of water polluted by A. baumannii in concentrations above 3 log CFU mL−1.

Bisphenol risk in fish exposed to a contamination gradient: Triggering of spatial avoidance

Bisphenol A (BPA) is an emerging contaminant widely used in various industrial products. Sublethal toxicity of BPA on aquatic organisms is expected to occur at a concentration of around 500 μg L−1, which is much higher than environmentally realistic concentrations found in water bodies (up to 0.41 μg L−1). However, there is no information concerning how a BPA contamination gradient could affect the spatial displacement of organisms. We hypothesized that fish might be able to detect an environmentally realistic BPA contamination gradient and avoid potential toxic effects due to continuous exposure. Therefore, the objectives of this work were: (i) to determine if BPA could trigger an avoidance response in the freshwater fish Poecilia reticulata; (ii) to assess whether BPA-driven avoidance occurs at environmentally relevant concentrations; and (iii) to estimate the population immediate decline (PID) at the local scale, considering avoidance and mortality as endpoints. Avoidance experiments were performed in a seven-compartment non-forced exposure system, in which a BPA contamination gradient was simulated. The results indicated that BPA triggered avoidance in P. reticulata. In a traditional forced acute toxicity test, lethal effects in 50% of the population occurred at a BPA concentration of 1660 μg L−1, while in the non-forced system with a BPA concentration gradient, avoidance of 50% of the population occurred at a concentration four orders of magnitude lower (0.20 μg L−1). At environmentally relevant BPA concentrations, PID was mainly determined by the avoidance response. Avoidance in P. reticulata populations is expected to occur at BPA concentrations below those that cause sublethal effects on fish and are considered safe by international agencies (≤1 μg L−1). The approach used in the present study represents a valuable tool for use in environmental risk assessment strategies, providing a novel and ecologically relevant response that is complementary to traditional ecotoxicological tests.

Artificial selection for food colour preferences.

Colour is an important factor in food detection and acquisition by animals using visually based foraging. Colour can be used to identify the suitability of a food source or improve the efficiency of food detection, and can even be linked to mate choice. Food colour preferences are known to exist, but whether these preferences are heritable and how these preferences evolve is unknown. Using the freshwater fish Poecilia reticulata, we artificially selected for chase behaviour towards two different-coloured moving stimuli: red and blue spots. A response to selection was only seen for chase behaviours towards the red, with realized heritabilities ranging from 0.25 to 0.30. Despite intense selection, no significant chase response was recorded for the blue-selected lines. This lack of response may be due to the motion-detection mechanism in the guppy visual system and may have novel implications for the evolvability of responses to colour-related signals. The behavioural response to several colours after five generations of selection suggests that the colour opponency system of the fish may regulate the response to selection.

Do freshwater ecoregions and continental shelf width predict patterns of historical gene flow in the freshwater fishPoecilia butleri?

We examined historical patterns of gene flow in the freshwater fish Poecilia butleri in western Mexico. We tested the hypothesis that the boundaries between four freshwater ecological communities (ecoregions) might have limited the movement of P. butleri because changes in species compositions might restrict establishment between adjacent ecoregions, even in situations where a physical barrier is absent. Hence, we predicted that boundaries between ecoregions should correspond to phylogeographical breaks in P. butleri. We also tested the hypothesis that the width of the continental shelf affected historical gene flow in P. butleri because a broad continental shelf provides a greater opportunity for rivers to coalesce during historical episodes of low sea levels as opposed to a narrow continental shelf that should restrict the potential for gene flow among adjacent rivers. Hence, we predicted greater amounts of historical gene flow among neighbouring river basins in the region of western Mexico where the continental shelf is wider, whereas, in the region where the continental shelf is narrower, we expected to detect limited levels of historical gene flow. We analyzed mitochondrial DNA sequence data (cytochrome b) taken from 264 individuals of P. butleri collected from 34 locations distributed across four different ecoregions in western Mexico. To examine patterns of phylogenetic diversification and historical gene flow in P. butleri, we employed several analytical approaches, including traditional tree-based phylogenetic analyses (likelihood and parsimony), haplotype network reconstruction, analyses of molecular variance, and spatial analysis of molecular variance. We found genetic breaks coinciding with two out of three different ecoregion boundaries, suggesting limited historical gene flow. In addition to different species compositions between these adjacent ecoregions, geological features such as the Trans-Mexican Volcanic Belt and the mountainous topography in south-western Mexico, likely contributed to these observed genetic breaks. By contrast, no genetic break was evident between two other ecoregions, a result that partially rejects our first hypothesis. Several results were consistent with our second hypothesis. Changes in the width of the continental shelf in western Mexico are associated with the observed patterns of historical gene flow. Our results indicate that the interactions among multiple geological and biological factors affect the spatial patterns of genetic diversity of widespread freshwater species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 399–416.

Homosexual behaviour increases male attractiveness to females

Male homosexual behaviour-although found in most extant clades across the Animal Kingdom-remains a conundrum, as same-sex mating should decrease male reproductive fitness. In most species, however, males that engage in same-sex sexual behaviour also mate with females, and in theory, same-sex mating could even increase male reproductive fitness if males improve their chances of future heterosexual mating. Females regularly use social information to choose a mate; e.g. male attractiveness increases after a male has interacted sexually with a female (mate choice copying). Here, we demonstrate that males of the tropical freshwater fish Poecilia mexicana increase their attractiveness to females not only by opposite-sex, but likewise, through same-sex interactions. Hence, direct benefits for males of exhibiting homosexual behaviour may help explain its occurrence and persistence in species in which females rely on mate choice copying as one component of mate quality assessment.

Inner ear morphology in the Atlantic molly Poecilia mexicana--first detailed microanatomical study of the inner ear of a cyprinodontiform species.

BackgroundFishes show an amazing diversity in hearing abilities, inner ear structures, and otolith morphology. Inner ear morphology, however, has not yet been investigated in detail in any member of the diverse order Cyprinodontiformes. We, therefore, studied the inner ear of the cyprinodontiform freshwater fish Poecilia mexicana by analyzing the position of otoliths in situ, investigating the 3D structure of sensory epithelia, and examining the orientation patterns of ciliary bundles of the sensory hair cells, while combining μ-CT analyses, scanning electron microscopy, and immunocytochemical methods. P. mexicana occurs in different ecotypes, enabling us to study the intra-specific variability (on a qualitative basis) of fish from regular surface streams, and the Cueva del Azufre, a sulfidic cave in southern Mexico.ResultsThe inner ear of Poecilia mexicana displays a combination of several remarkable features. The utricle is connected rostrally instead of dorso-rostrally to the saccule, and the macula sacculi, therefore, is very close to the utricle. Moreover, the macula sacculi possesses dorsal and ventral bulges. The two studied ecotypes of P. mexicana showed variation mainly in the shape and curvature of the macula lagenae, in the curvature of the macula sacculi, and in the thickness of the otolithic membrane.ConclusionsOur study for the first time provides detailed insights into the auditory periphery of a cyprinodontiform inner ear and thus serves a basis—especially with regard to the application of 3D techniques—for further research on structure-function relationships of inner ears within the species-rich order Cyprinodontiformes. We suggest that other poeciliid taxa, or even other non-poeciliid cyprinodontiforms, may display similar inner ear morphologies as described here.

Inner ear morphology in the Atlantic molly Poecilia mexicana

Fishes show an amazing diversity in hearing abilities, inner ear structures, and otolith morphology. Inner ear morphology, however, has not yet been investigated in detail in any member of the diverse order Cyprinodontiformes. We, therefore, studied the inner ear of the cyprinodontiform freshwater fish Poecilia mexicana by analyzing the position of otoliths in situ, investigating the 3D structure of sensory epithelia, and examining the orientation patterns of ciliary bundles of the sensory hair cells, while combining μ-CT analyses, scanning electron microscopy, and immunocytochemical methods. P. mexicana occurs in different ecotypes, enabling us to study the intra-specific variability (on a qualitative basis) of fish from regular surface streams, and the Cueva del Azufre, a sulfidic cave in southern Mexico. The inner ear of Poecilia mexicana displays a combination of several remarkable features. The utricle is connected rostrally instead of dorso-rostrally to the saccule, and the macula sacculi, therefore, is very close to the utricle. Moreover, the macula sacculi possesses dorsal and ventral bulges. The two studied ecotypes of P. mexicana showed variation mainly in the shape and curvature of the macula lagenae, in the curvature of the macula sacculi, and in the thickness of the otolithic membrane. Our study for the first time provides detailed insights into the auditory periphery of a cyprinodontiform inner ear and thus serves a basis--especially with regard to the application of 3D techniques--for further research on structure-function relationships of inner ears within the species-rich order Cyprinodontiformes. We suggest that other poeciliid taxa, or even other non-poeciliid cyprinodontiforms, may display similar inner ear morphologies as described here.

Behavioural and histochemical changes induced by osmotic stress in Poecilia reticulata Peters (pisces, cyprinodontidae)

1. 1. Behavioural activities and histochemical changes of mucopolysaccharides, ATPase and respiratory enzymes in the gill epithelium of freshwater fish Poecilia reticulata Peters were examined at different times after 100% sea-water exposure. 2. 2. Acute stress was observed in the first 6 hr, with behavioural and histochemical changes. 3. 3. Up to 6 hr reduction in reaction activities of succinic-dehydrogenase, cytochrome-oxidase, ATPase and mucopolysaccharides was observed. 4. 4. After the first 6 hr a strong increase in ATPase and respiratory enzymes levels was observed until they reached levels similar to the controls at 7 days. Mueopolysaccharide reactions were gradually reduced and disappeared completely at 7 days. 5. 5. Behavioural adaptations changed in the same time and behavioural activity appeared normal at 24 hr. 6. 6. A correlation between the adaptive flexibility of P. reticulata and morphological and physiological characters is hypothesized.

Histopathological effects in Poecilia reticulata (guppy) exposed to methyl mercury chloride.

To evaluate the usefulness of histopathology in aquatic toxicity testing, studies were carried out on the small freshwater fish Poecilia reticulata (guppy) following aqueous methyl mercury chloride exposure. Fish were exposed to concentrations of 0, 1.0, 1.8, 3.2, 5.6, or 10 micrograms/L for 1 and 3 months. Histopathological changes included the occurrence of multiple granulomas in various tissues, in particular, the integument and orbit. These changes were accompanied by hyperplasia of monocytopoietic interrenal tissue, and hepatocellular change which was confirmed by morphometry. The latter findings were probably a result of monocyte "consumption" by granulomas, and hepatic synthesis of ("stress") proteins, respectively. The bile duct and, focally, the proximal intestine, showed hyperplasia of the epithelium. In the testis of sexually mature fish (3-month study), degeneration and necrosis of sperm occurred, with severe cases exhibiting Sertoli cell hypertrophy, interstitial inflammation, and absence of mature sperm. Epidermal mucous cells disappeared in the highest concentration used, and, after 3 months, clusters of undifferentiated basophilic cells were seen in the gas gland, which occasionally were suggestive of malignant growth. The changes in the kidney tubules were characterized by degeneration and necrosis of single cells which also showed mitotic figures. This is considered a result of the mitosis-disturbing activity of methyl mercury (MeHg). It is concluded that MeHg has effects on various target organs in guppies with the occurrence of granulomas as the most sensitive indicator, yielding a no-observed-effect concentration (NOEC) of 1.0 micrograms/L. In contrast to mammalian species, no morphologic evidence for neurotoxicity was found.

Pathological effects in freshwater fish Poecilia reticulata (guppy) and Oryzias latipes (medaka) following methyl bromide and sodium bromide exposure

To study the effects of the fumigant methyl bromide (CH 3Br) and its anorganic residue, bromide (Br −), young guppies and medakas were exposed to these chemicals for 1 and 3 months. The concentration ranges were 10–32 000 mg/l (guppy) and 180–5 600 mg/l (medaka) for NaBr and 0.032–3.2 mg/l for CH 3Br. Besides monitoring of general toxicological parameters, histopathology was performed on total body sections. In addition, a short-term study with the two highest concentrations CH 3Br was conducted for the evaluation of (lethal) effects, in which scanning electron microscopy of the gills was included. In the guppy, a NaBr concentration of 100 mg/l and higher caused paresis and paralysis. Histopathology of these animals, exposed to concentrations of 3 200 mg/l, showed muscle changes indicative of a functional neuromuscular disturbance. In the thyroid, the epithelium appeared to be stimulated (at 32 and 100 mg/l and higher after 1 and 3 months' exposure, respectively), and the thyroid stimulating hormone producing cells in the pituitary were also activated. The development of gonads in both sexes was more advanced than in the controls after the 3-month exposure period, and there was inflammation in and around the larger blood vessels in the abdomen at concentrations of 3 200 mg/l and higher after 3 months. Medakas showed only activation of the thyroid epithelium even at the lowest concentration tested (180 mg/l). In the CH 3Br study, no specific effects were observed in the long-term study of either species. In the short-term study, however, major degenerative and regenerative changes were found in the superficial epithelia, especially of the gills and oral mucosa. These were apparently caused by the local irritating action of this compound. Moreover, at these lethal concentrations, necrotic alterations were seen in the thymic cortex and the testis which were considered stress-related. In this context, the importance of gill lesions is discussed. It is concluded that Br − is goitrogenic in both species at low concentrations, and in guppies, at higher concentrations, it also affects skeletal muscle, blood vessels and gonads. Methyl bromide has no specific action but is irritating for superficial epithelia at relatively high concentrations.