Effects of octylphenol and 17beta-estradiol on the gonads of guppies (Poecilia reticulata) exposed as adults via the water or as embryos via the mother

Effects of maternal exposure to environmentally relevant concentrations of 17α-ethinyloestradiol in a live bearing freshwater fish, Xenotoca eiseni (Cyprinodontiformes, Goodeidae)

The viviparous teleost Redtail Splitfin (Xenotoca eiseni) is a live bearing fish that presents a novel freshwater model for investigating the effects of maternally derived micropollutants on vulnerable early developmental life stages. Here, adult female X. eiseni were exposed to 17α-ethinyloestradiol (EE2), a potent contraceptive oestrogen, at environmentally relevant concentrations, to investigate for effects on sex partitioning and development. Pregnant and non-pregnant females were exposed for four weeks to EE2 at measured concentrations of 0.9 and 3.4 ng/L EE2 and offspring from gravid females were kept in clean water for a further four weeks. Only pregnant females were seen to respond to 3.4 ng/L EE2 with an increase in the transcription of hepatic vitellogenins (vtgA, vtgB and vtgC). Offspring of exposed mothers showed no obvious effects on somatic growth, gonadal development, sex partitioning or development. However, there was a higher rate of deformities and developmental abnormalities in offspring of EE2-exposed females. The work presented provides the foundation for the development of X. eiseni as a new freshwater model for studies on maternal transfer of chemical pollutants in live bearing animals.

The effect of tertiary treated wastewater on fish growth and health: Laboratory-scale experiment with Poecilia reticulata (guppy)

Treated wastewater (TWW) constitutes a sustainable water resource and has been used for fish culture in some countries around the world, although there are no comprehensive data on the effect of TWW on fish growth and health in the context of aquaculture production. Our objectives were to examine how fish culture in TWW affected fish growth and fitness, as well as compliance with the international standards for safe consumption. Guppy (Poecilia reticulata) fingerlings were reared in 0%, 50% and 100% tertiary TWW (TTWW), from the age of five days, for a period of four months. In water analyses, 33 out of 67 tested organic micropollutants (OMPs) were detected in the TTWW samples at least once, at concentrations that are typically reported in domestic TTWW. Fish survival ranged between 77-80% and did not differ between treatment groups. Fish growth and mortality following challenge infection with Tetrahymena sp. (which ranged between 64-68%), were similar among treatment groups. Of tested immunological parameters, lysozyme and anti-protease was similar among treatments while complement activity was highest in the 50% TTWW-reared fish. No abnormalities were observed in the histopathological analysis. Levels of heavy metals, polychlorinated-biphenyls (PCBs) and organochlorines (OCs) in fish were below the detection limit and below the Food and Agriculture Organization of the United Nations (FAO) and the European Union EU maximal permitted levels in food fish. Results suggest that the yield of fish grown in TTWW is potentially similar to that in freshwater, and the produced fish comply with the standards of consumer safety. The results are in line with previous studies that examined the feasibility of TWW-fed aquaculture.

Quality evaluation of sperm from livebearing fishes: Standardized assessment of sperm bundles (spermatozeugmata) from Xenotoca eiseni (Goodeidae)

Standardized evaluation of sperm quality is essential for research, commercial-scale cryopreservation, and induced spawning. However, standardized methods for evaluation of sperm bundles (spermatozeugmata or spermatophores) have not been established. The purpose of the present study was to use Redtail Splitfin (Xenotoca eiseni) as a model for freshwater livebearing fishes to establish initial standardized methods to collect sperm bundles, and quantitatively and qualitatively evaluate quality-related attributes. No sperm or sperm bundles were able to be collected by stripping. Testes were removed, rinsed, weighed, placed in 50 μL of buffer solution on a glass slide, and crushed gently 3-5 times with angled spade-tip forceps. Sperm bundles were released into the buffer solution and collected with a pipette into 1.5-mL centrifuge tubes. To quantify size and shape, images of bundles were captured with a CCD camera connected to a microscope, and measured with computer software. There was no significant correlation between body wet weight and major bundle axis length (P = 0.6759), minor axis length (P = 0.5658), average axis length (P = 0.5869), aspect ratio (P = 0.7839), and observed area (P = 0.5727). The concentrations of sperm bundles, estimated with the three methods (Makler® counting chamber, a hemocytometer, and direct counting) were significantly different (P < 0.0001). Hemocytometers were suitable for estimation of bundles from X. eiseni. To evaluate activation of sperm, bundles were viewed with a microscope, and classified into one of five phases by evaluating morphology of the bundles and motion of sperm within the bundles as Phase 0 through Phase 4 that represented early through late activation stages. The frequencies and duration of each activation phase were used to evaluate dissociation of sperm bundles and motility capability of sperm within the bundles. Within 180 min of activation, all five phases were observed. Overall, this study for the first time established standardized methods to collect and evaluate quality-related attributes of sperm bundles. These standardized evaluations provide a basis for further modification, standardization, and generalization, which are useful in research on livebearing fishes involving male gametes, such as studies on cryopreservation, artificial insemination, and in development of germplasm repositories for imperiled species including goodeids.

Effects of BPF on steroid hormone homeostasis and gene expression in the hypothalamic-pituitary-gonadal axis of zebrafish

Bisphenol F (BPF) has been frequently detected in various environmental compartments, and previous studies found that BPF exhibits similar estrogenic and anti-androgenic effects on the mammalian endocrine system to those of bisphenol A (BPA). However, the potential disrupting effects of BPF on aquatic organisms and the underling disrupting mechanisms have not been investigated. In this study, the potential disrupting mechanisms of BPF on the hypothalamic-pituitary-gonadal (HPG) axis and liver were probed by employing the OECD 21-day short-term fecundity assay in zebrafish. The results show that BPF exposure (1 mg/L) impaired the reproductive function of zebrafish, as exemplified by alterations to testicular and ovarian histology of the treated zebrafish. Homogenate testosterone (T) levels in male zebrafish decreased in a concentration-dependent manner, and 17β-estradiol (E2) levels increased significantly when fish were exposed to 0.1 and 1 mg/L BPF. The real-time polymerase chain reaction was performed to examine gene expression in the HPG axis and liver. Hepatic vitellogenin expression was significantly upregulated in males, suggesting that BPF possesses estrogenic activity. The disturbed hormone balance was enhanced by the significant changes in gene expression along the HPG axis. These alterations suggest that BPF leads to adverse effects on the endocrine system of teleost fish, and that these effects were more prominent in males than in females.

Brain nonapeptide and gonadal steroid responses to deprivation of heterosexual contact in the black molly

Fish may respond to different social situations with changes in both physiology and behaviour. A unique feature of fish is that social interactions between males and females strongly affect the sexual characteristics of individuals. Here we provide the first insight into the endocrine background of two phenomena that occur in mono-sex groups of the black molly (Poecilia sphenops): masculinization in females and same-sex sexual behaviour, manifested by gonopodial displays towards same-sex tank mates and copulation attempts in males. In socially controlled situations, brain neurohormones impact phenotypic sex determination and sexual behaviour. Among these hormones are the nonapeptides arginine vasotocin (AVT) and isotocin (IT), counterparts of the well-known mammalian arginine vasopressin and oxytocin, respectively. To reveal potential hormone interactions, we measured the concentrations of bioactive AVT and IT in the brain, along with those of the sex steroids 17β-estradiol and 11-ketotestosterone in the gonads, of females, masculinized females, males displaying same-sex sexual behaviour and those who did not. These data were supplemented by morphological and histological analyses of the gonads. Correlations between brain nonapeptides and gonadal steroids strongly suggest a cross talk between hormonal systems. In the black molly, the masculinization process was associated with the production of brain AVT and gonadal steroids, whereas same-sex sexual behaviour involves both brain nonapeptides, but neither of the sex steroids. This study extends current knowledge of endocrine control of phenotypic sex and sexual behaviour in fish and for the first time links brain nonapeptides with the occurrence of male-male sexual behaviour in lower vertebrates.

Phytoestrogens β -sitosterol and genistein have limited effects on reproductive endpoints in a female fish, Betta splendens

Phytoestrogens are produced by plants and may cause endocrine disruption in vertebrates. The present study hypothesizes that phytoestrogen exposure of female Siamese fighting fish (Betta splendens) may disrupt endogenous steroid levels, change agonistic behavior expression, and potentially also disrupt oocyte development. However, only the pharmacologic dose of β-sitosterol had a significant effect on opercular flaring behavior, while we did not find significant effects of β-sitosterol or genistein on steroids or gonads. These findings are in direct contrast with previous studies on the effects of phytoestrogens in female fish. Results of the current study support previous work showing that the effects of phytoestrogen exposure may be less acute in mature female B. splendens than in other fish.

Effects of the fungicide prochloraz on the sexual development of zebrafish (Danio rerio)

Some chemicals have the potential to adversely affect sexual development through multiple endocrine actions. Prochloraz is an imidazole fungicide that displays diverse mechanisms of action, including inhibition of aromatase activity, inhibition of androgen synthesis, and antagonism of the androgen receptor. The objective of this study was to assess the effects of prochloraz on the sexual development of zebrafish (Danio rerio) in the Fish Sexual Development Test (FSDT) proposed as an OECD test guideline for detection of endocrine disruptors. Zebrafish were exposed to prochloraz (0, 16, 64 or 202 microg/L) for 60 days from 24 h post fertilization. Fish exposed to 202 microg/L prochloraz showed an increased proportion of males. Furthermore, the incidence of intersex and the stages of the gonads were altered in the treated fish compared to the control fish. A significant vitellogenin decrease was observed in both female and male zebrafish at an exposure concentration of 202 microg/L prochloraz. However, in the male fish, significantly increased vitellogenin concentrations were observed in the groups exposed to 16 or 64 microg/L prochloraz. This study serves as a part of the validation of the FSDT and indicates that the FSDT is suitable in detecting compounds with multiple endocrine actions. This is of importance in the assessment of the potential risk of existing and new chemicals.

The effects of Gokshura, Tribulus terrestris on sex reversal of guppy, Poecilia reticulata

This study examined the effects of Tribulus terrestris (TT) on sex reversal in guppy, Poecilia reticulata. The objective of this study was to introduce a new environmentally friendly method for masculinization in P. reticulata. Since male guppy has higher commercial value than female. TT is a natural, non-toxic herb which helps enhance testosterone levels in human and animals. It was prepared in a laboratory in France. Different concentration (0.0, 0.05, 0.1 and 0.15 g L(-1)) of TT was investigated for sex reversal in the Poecilia reticulata. TT extract was administered by immersion of newly born offspring once weekly for two months. Among the dosages used in the present study 0.15 g L(-1) TT was the most effective dosage that ensured maximum male ratio (80%, p < 0.01). Although, sex ratios of 0.05 and 0.1 g L(-1) TT were not significantly different from the expected 1:1 ratio, in these two groups treatment with TT also result in higher number of males (58.25 and 59.77%, respectively), than control (p > 0.05). Total survival rates in all treatments and control were uniformly high ranging from 83 to 87% (p > 0.05). It is concluded that TT has no negative effect on survival rate of P. reticulata. All groups of TT-treated fish exhibited successful growth acceleration comparing to the control group, but only TT treatment at the concentration of 0.15 and 0.1 g L(-1) TT significantly improved growth rate of P. reticulata (p < 0.01). Histological examinations revealed that testes of fish treated with TT-extract contained all stages of spermatogenesis. Sex reversal in P. reticulata demonstrated that TT treated new-born progenies showed successful sex reversal, spermatogenesis and better growth rate than untreated progenies.

Review of evidence: are endocrine-disrupting chemicals in the aquatic environment impacting fish populations?

In this paper, evidence from the current literature is presented that addresses either of two questions: 1) do EDCs in the aquatic environment have the potential to impact the reproductive health and survival of various fish species, and 2) are EDCs in the aquatic environment actually impacting the reproductive health and sustainability of indigenous populations of fish? Overall, data from laboratory experiments support the hypothesis that EDCs in the aquatic environment can impact the reproductive health of various fish species, but evidence that EDCs in the aquatic environment are actually impacting the reproductive health and sustainability of indigenous fish populations is less convincing. The scarcity of evidence linking impacts of environmental EDCs with changes in reproductive success of indigenous fish populations may reflect a critical need for a dependable method or indicator to assess reproduction of fish in situ. In addition, more studies that investigate whether fish populations routinely exposed to EDCs in situ are experiencing changes in population structure are needed. Linking endocrine disruption and reproductive impairment with an ecologically relevant impact on the sustainability of real fish populations remains, with few exceptions, an open challenge.

Plasma vitellogenin levels and gonadal morphology of wild carp (Cyprinus carpio L.) in a receiving rivers downstream of sewage treatment plants

A field study was carried out in order to assess, in a wild cyprinid fish, the biological effects related to the exposure to estrogenic compounds. The gonadosomic index (GSI), plasma vitellogenin (VTG) level and histological observations of gonads were performed to evaluate the reproductive health in common carp (Cyprinus carpio) from three rivers receiving sewage treatment plant (STP) effluents (Guadarrama, Henares and Jarama rivers, Spain) and from a reference site (Lozoya river). No significative differences in male GSI between sites were described. Only in the 18% of fish from Guadarrama river were elevated plasma VTG levels detected. The presence of oocytes in the testis was not found in any of males examined. The results suggest that the released estrogenic compounds by STPs effluents are not enough capable to adversely affect the gonadal development of the fish studied. Additional studies will be required to assess the risk of estrogenic compounds on fish from other sites of this area.

Effects of the wood extractive betulinol and 17beta-oestradiol on reproduction in zebrafish, Danio rerio (Hamilton)--complications due to a bacterial infection

Zebrafish were exposed to the wood extractive betulinol (5 microg L(-1)) and to 17beta-oestradiol (E2, 0.27 microg L(-1)) for 8 weeks in an attempt to study the possible endocrine-disrupting activity of betulinol. Females exposed to betulinol showed increased spawning intensity, while males exposed to betulinol and E2 had increased incidences of structural alterations in the testes. However, histological examination of the fish revealed that they were infected by acid-fast bacteria suspected to be Mycobacterium sp. despite a careful examination of their health state prior to the onset of the experiment. Fish exposed to betulinol and E2 showed more serious consequences of the bacterial infection than control fish indicating that the test chemicals had weakened the immune defence of the fish. When the exposure was repeated with healthy fish, an increase in the proportion of spermatogonia was seen in the testes of betulinol-treated males. A similar alteration, although not statistically significant, was also seen in the first experiment. However, no increase in the incidences of structural alterations in the testes was seen in betulinol- and E2-treated fish in the second experiment. Our study indicates that betulinol might have an endocrine-disrupting effect in zebrafish, but the increase in incidences of structural alterations in the testes might have been caused by a synergistic action between the test compounds and the bacterial infection. Our study stresses the importance of carefully checking the health of experimental fish, not only prior to the onset of an experiment but also upon termination of the experiment, in order to avoid misinterpretation of the results.