Endosulfan affects GnRH cells in sexually differentiated juveniles of the perciform Cichlasoma dimerus (original) (raw)
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Aquatic Toxicology, 2013
Endosulfan (ES), a persistent organochlorine pesticide, is widely used despite its toxicity to non-target animals. Upon reaching water bodies, ES can cause negative effects on aquatic animals, including disruption of hormonal systems. However, the action of ES on fish reproductive axis has been hardly studied thus far. The aim of the present work was to assess the endocrine disruptive potential of endosulfan on the pituitary gonadotropins levels and on the testes function due to ES in the South American freshwater fish Cichlasoma dimerus, using in vitro and in vivo approaches. In vitro experiments showed that ES inhibited the LH-stimulated steroidogenesis in gonads; no change was observed in gonadotropins release from pituitaries in culture. Laboratory waterborne ES (0.1, 0.3 and 1 g/L) exposure for two months caused decrease in FSH pituitary content and ␥GT activity in the testes (Sertoli cell function marker). Testicular histology revealed pathologies such as scarce intermediate stages of spermatogenesis, release of immature germ cells into the lobular lumen, presence of foam cells and interstitial fibrosis. As FSH and FSH-mediated steroidogenesis regulate spermatogenesis and Sertoli cell function, the effect of ES on FSH could be responsible for the morphological alterations observed in testes. In vitro, ES disrupted steroidogenesis in gonads, therefore similar effects in vivo cannot be ruled out. Based on this evidence, ES exhibits an endocrine disruptive action on the reproductive axis of C. dimerus, causing disruption at the pituitary and/or at the gonad level. These effects could acquire ecological significance under prolonged exposure to the pesticide in nature.
Ecotoxicology and Environmental Safety, 2016
Estrogenic chemicals are often detected in the aquatic environment and can negatively affect animal development and reproduction. In teleost fishes, the hormonal regulation during a critical period of larval development has a strong influence on gonadal sex differentiation; thus this process may be affected by the exposure to environmental estrogens. In this study, we first assessed the lethal acute toxicity of the natural estrogen 17β-estradiol (E 2) and the weaker estrogen mimics 4-tert-octylphenol (OP) and 4-nonylphenol (NP) on larval stages of the South American cichlid fish Cichlasoma dimerus. In a further experiment, we analyzed the effects of chronic waterborne exposure to E 2 and OP on gonad development and sex differentiation. Exposure to high concentrations of E 2 had a pronounced feminizing effect directing sex differentiation towards ovarian development, while testis development was inhibited at a lower, environmentally relevant concentration. Among OP-exposed fish, 15-38.5% of the males exhibited testicular oocytes (TOs), a commonly reported biomarker of estrogenic exposure. However, since TOs were also recorded in control males and the proportion of males with TOs was not significantly higher in OP treatments, their occurrence could not be attributed to OP exposure. In addition, TOs did not seem to impair male gonad development and functionality since normal spermatogenesis was observed in testes of OP-treated fish. These results indicate that E 2 occurring in the South American aquatic environment may affect male reproductive development and pose a risk for wild C. dimerus, especially under prolonged exposure, while the effects of weaker xenoestrogens such as OP would be negligible for gonad development in this species. As illustrated by this study, the natural occurrence of TOs indicates that conclusions concerning the causes of this phenomenon must be drawn with care.
Endocrine Toxicants and Reproductive Success in Fish
Human and Ecological Risk Assessment: An International Journal, 2001
There is compelling evidence on a global scale for compromised growth and reproduction, altered development, and abnormal behaviour in feral fish that can be correlated or in some cases causally linked with exposure to endocrine disrupting chemicals (EDCs). Attributing cause and effect relationships for EDCs is a specific challenge for studies with feral fish as many factors including food availability, disease, competition and loss of habitat also affect reproduction and development. Even in cases where there are physiological responses of fish exposed to EDCs (e.g., changes in reproductive hormone titres, vitellogenin levels), the utility of these measures in extrapolating to whole animal reproductive or developmental outcomes is often limited. Although fish differ from other vertebrates in certain aspects of their endocrinology, there is little evidence that fish are more sensitive to the effects of EDCs. Therefore, to address why endocrine disruption seems so widespread in fish, it is necessary to consider aspects of fish physiology and their environment that may increase their exposure to EDCs. Dependence on aquatic respiration, strategies for iono-osmotic regulation, and maternal transfer of contaminants to eggs creates additional avenues by which fish are exposed to EDCs. This paper provides an overview of responses observed in feral fish populations that have been attributed to EDCs and illustrates many of the factors that need consideration in evaluating the risks posed by these chemicals.
Archives of Environmental Contamination and Toxicology, 2010
Endocrine-disrupting chemicals can influence the hypothalamus-pituitary-gonad axis and possibly affect reproduction in vertebrates. We analyzed the effect of 30day endosulfan (ES) exposure in sexually undifferentiated larvae of the cichlid fish Cichlasoma dimerus. The number, area, mean cytoplasmic and nuclear diameter, and mean cytoplasmic optical density of gonadotropin-releasing hormone (GnRH) I, II, and III immunoreactive (ir-) neurons and b follicle-stimulating hormone (bFSH) ir-cells were measured. Animals exposed to the highest ES concentration (0.1 lg/l) showed a decrease in GnRH I nucleus/cytoplasm area ratio upon exposure. Nuclear area and mean nuclear diameter of bFSH ir-cells was higher in ES treated fish. bFSH nucleus/cytoplasm area ratio was high in exposed animals, and animals exposed to 0.1 lg/l ES showed smaller mean cytoplasmic optical density. These findings suggest that ES affects GnRH I and bFSH protein synthesis/release. However, these responses seem to be insufficient to affect gonadal differentiation at this stage of development.
Critical Reviews in Toxicology, 2012
Endocrine disrupting chemicals (EDCs) enter aquatic ecosystems through discharged effluents, mainly from wastewater treatment works and diffuse run off from land, and affect a wide range of aquatic biota, including fish. Evidence for altered physiology in fish as a consequence of endocrine disruption is global, with some of the most widely reported effects on sexual development and function. In recent years research has shown that fish behaviors can also be affected by EDCs which potentially has wide implications for individual fitness and population level outcomes. This review presents a critical assessment on reported effects of EDCs on behavior in fish, focusing on behaviors associated with reproduction. We investigate commonalities and differences in sexual behaviors between fish species most commonly applied in ecotoxicology, drawing out common principles for impacts of EDCs and then reviewing the evidence for, and implications of, disruptions of these behaviors after exposures to EDCs. In an analysis of the reported effects of exposure to the estrogen, ethinylestradiol, we show that life-stage at exposure is a key factor determining behavioral responses of affected populations. EDC-induced changes in behavior occur at similar concentrations as for established biomarker responses (e.g. vitellogenin induction for estrogens), indicating behavior is equally sensitive (and non-invasive) as an indicator of EDC exposure. Adopting behaviors in fish as indicators of chemical exposure and effects, however, still has many technical and interpretation challenges and there is very little information available on how behaviors under laboratory conditions equate with those occurring in wild populations.
Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 2016
The organochlorine pesticide endosulfan (ES) is used in several countries as a wide spectrum insecticide on crops with high commercial value. Due to its high toxicity to non-target animals, its persistence in the environment and its ability to act as an endocrine disrupting compound in fish, ES use is currently banned or restricted in many other countries. Previous studies on the cichlid fish Cichlasoma dimerus have shown that waterborne exposure to ES can lead to both decreased pituitary FSH content and histological alterations of testes. As gonadotropin-stimulated sex steroids release from gonads was inhibited by ES in vitro, the aim of the present study was to elucidate possible mechanisms of disruption of ES on gonadal steroidogenesis in C. dimerus, as well as compare the action of the active ingredient (AI) with that of currently used commercial formulations (CF). Testis and ovary fragments were incubated with ES (AI or CF) and/or steroidogenesis activators or precursors. Testo...
Environmental Toxicology, 2006
A reservoir receiving some sewage water from an urban area, in addition to fresh water sources, was used for raising three species of fish. Prior to the introduction of the fish, the reservoir water contained appreciable amounts of testosterone, estrogen, ethinylestradiol and medroxyprogesterone. After introduction of the fish the level of hormones and drugs were reduced to nearly non-detectable levels while in a control reservoir without fish, the levels of the compounds remained constant. Of the three species studied, after eight months only the female carp developed gonads, which were small for body size. Observations suggest that the fish absorb the hormones and drugs in the early growing season and this has a negative effect on their reproductive development.
Ecotoxicology and Environmental Safety, 2003
The EU-funded project IDEA aimed to evaluate (a) what parameters and endpoints allow the detection of endocrine-mediated developmental and reproductive effects of (xeno)estrogens in life cycle-and life stage-specific toxicity tests with the zebrafish Danio rerio, a small laboratory fish used in many ecotoxicity test guidelines, and (b) whether substances that act as estrogens in vertebrates may also adversely affect the development, differentiation, and reproduction of aquatic invertebrates. The invertebrate species investigated included Hydra vulgaris, Gammarus pulex, Chironomus riparius, Hyalella azteca, and Lymnaea stagnalis. The animals were exposed to the model estrogenic chemicals ethynylestradiol (EE2), bisphenol A (BPA), and octylphenol (OP), which exert their endocrine activity in vertebrates through the estrogen receptor. As endpoints, developmental and reproductive parameters at the organism level as well as molecular and cellular parameters were measured. Life cycle exposure of zebrafish to (xeno)estrogens induced a specific, partly irreversible response pattern, consisting mainly of (a) induction of vitellogenin (VTG), (b) alterations of gonad differentiation, (c) delay of first spawning, and (d) reduced fertilization success. The effects of EE2 on zebrafish were expressed at environmentally realistic concentrations, while BPA and OP became effective at concentrations higher than those usually found in the environment. The vitellogenic response was equally sensitive as the reproductive parameters in the case of EE2, but VTG was more sensitive in the case of BPA. Partial life cycle exposure of zebrafish had lasting effects on fish development and reproduction only when the fish were exposed during the stage of juvenile bisexual gonad differentiation. In (partial) life cyle and multigeneration studies with invertebrates, (xeno)estrogenic impact was assessed by a range of developmental and reproductive parameters including hatching, growth, moulting, mating behavior, and egg number. Several parameters were found to be responsive to (xeno)estrogens; however, most effects were induced only at higher, probably nonphysiological concentrations. Lowdose effects were observed in full life cycle experiments, particularly in the second generation. It remains to be established whether the estrogen-induced alterations in the invertebrate species indeed do result from disturbances of the endocrine system. The findings of the present research project support the development of appropriate testing methodologies for substances with estrogenic activity. r 2002 Elsevier Science (USA). All rights reserved. 0147-6513/03/$ -see front matter r 2002 Elsevier Science (USA). All rights reserved. PII: S 0 1 4 7 -6 5 1 3 ( 0 2 ) 0 0 0 3 9 -8
Aquatic Toxicology, 2006
The Endocrine Modulators Study Group (EMSG) of the European Chemical Industry has proposed an extended fish early-life stage (ELS) test based on OECD test guideline 210 in combination with a fish pair-breeding reproduction study as a possible alternative for fish full life cycle testing. In this paper the androgen methyldihydrotestosterone (MDHT) was tested in an extended ELS test with fathead minnow supplementary to such a test with the weak estrogen 4-tert-pentylphenol (4TPP). Main endpoints were secondary sexual characteristics (SSC), plasma vitellogenin (VTG) induction and gonadal development. Early blastula embryos were exposed to 0, 0.10, 0.32 and 1.0 g MDHT l −1 for up to 114 days post-hatch (dph). A batch of fish exposed to 1.0 g l −1 was transferred to clean water after 30 or 63 dph for the remainder of the study. Ethinylestradiol (EE2) was included as estrogenic reference substance at 0.01 g l −1 . Exposure to MDHT had no significant effect on hatching success or survival, but significantly increased the condition factor of fish exposed for 63 and 114 dph (up to 150% of the control). At 63 dph MDHT exposure induced appearance of tubercles on the snout (a male SSC) of more than 80% of fish. Compared to the controls, plasma VTG was not detectable or significantly lower in fish exposed to MDHT at 0.10 g/l, but not significantly affected at higher MDHT concentrations. Both lower levels of MDHT significantly inhibited the development of female gonads as of 30 dph. Fish exposed to MDHT at 0.32 and 1.0 g l −1 showed higher incidences of mixed sex gonads (10-25%) and smaller testes or dysplasia of gonadal tissue. Dysplasia was present in 80% of the fish continuously exposed to 1.0 g l −1 up to 114 dph, but reversible when fish were transferred to dilution water. Results indicate that suppression of ovarian development was the most sensitive endpoint for MDHT exposure after 30 dph. Other endpoints (e.g., growth and SSC) required exposure during at least up to 63 dph to yield a significant effect. Androgenic effects on VTG production required even longer exposure, i.e., until sufficient number of females had matured.
World, 2012
The aquatic ecosystem is one of the most exposed environments to pollutants. A lot of xenobiotics are known to disrupt the reproductive endocrine system. Fish are one of the primary risk organisms for Endocrine Disrupting Chemicals [EDCs]. In common with all vertebrates, reproduction in fish is controlled by the Hypothalamic-Pituitary-Gonad-Liver [HPGL] axis. The multitude of hormones controlling this axis and the complexity of hormones regulation, make from the HPGL axis a major target of EDCs. Variation of hormones synthesis levels, disturbance of genes expression, alteration of gonads structure and disruption of liver functions were noted. HPGL axis represents so one of the most important endpoints in the risk assessment of EDCs. In this review, we seek to extract from recent literature concepts regarding the effects of EDCs on the endocrine reproductive system in fish that might be of interest to explain some alterations in the wide populations of fish.