Temporal evolution of imposex and butyltin contamination in Gemophos viverratus from São Vicente (Cabo Verde) - a countercurrent trend on the world scenario

Organotin (OT) based Antifouling Systems (AFS) were globally banned by the AFS Convention since 2008, but the Republic of Cabo Verde did not ratify this Convention, nor did it develop a national legislation to control OT-AFS. Gemophos viverratus imposex and butyltin tissue contamination were assessed around the São Vicente Island (Cabo Verde) in 2019 and compared with the data available from 2012. The vas deferens sequence index (VDSI), the relative penis length (RPL), the percentage of females with imposex (%I) and the percentage of sterilized females (%S) in 2019 ranged from 0 to 4.0, 0-84.4%, 0-100% and 0-5.1%, respectively, whilst TBT reached maximum values of ≈30 ng TBT-Sn g^-1 dw in the whelk tissues. These values are very similar to those registered in 2012, which indicates that TBT pollution has not decreased over the years, in contrast to the declining trend observed worldwide.

The Occurrence of Intersex in Different Populations of the Marine Amphipod Echinogammarus marinus in North-West Brittany - A Longterm-Study

In the past two decades, an increasing body of studies has been published on the intersex phenomenon in separate-sexed crustaceans from marine and freshwater ecosystems. Various causes are being considered that could have an influence on the occurrence of intersex. Besides genetic factors, environmental conditions such as photoperiodicity, temperature, salinity and parasitism, but also environmental pollution with endocrine disrupting chemicals (EDCs) are discussed. As part of a long-term monitoring (2012 - 2020) in north-west Brittany, we recorded the occurrence of intersex in the marine amphipod Echinogammarus marinus. We quantified the intersex incidence at marine and estuarine sites and analyzed the incidence in relation to the endocrine potential of the sediments. Intersex occurred with mean frequencies between 0.87% and 12%. It was striking that the incidence of intersex increased with increasing distance from the sea. Since the highest incidence was observed at the range boundary of this stenohaline species, we assume that intersex is triggered by endocrine potential and increasing stress due to increasing freshwater content - and thus an interplay of different environmental factors.

Imposex Incidence in Gastropod Species from Santa Marta Coastal Zone, Colombian Caribbean Sea

Imposex is a phenomenon widely associated with environmental exposure to organotin compounds which were quite common components of antifouling paints applied on boats and ship hulls. Here we study the incidence of imposex in neogastropods and its relation with water quality and maritime traffic in the coastal strip of Santa Marta, Colombia. Imposex was determined via specialized indexes and related to the organisms' size, somatic conditions, variables of water quality and maritime traffic, in a space-time assessment. There was evidence of imposex in five species Plicopurpura patula, Vasula deltoidea, Stramonita haemastoma, S. floridana, and Gemophos auritulus. Purpura patula and Vasula deltoidea species were found in all sampling sites. The results have proved that imposex is highly influenced by the maritime traffic variable, with greater prevalence during the dry season, and with P. patula being more sensitive than V. deltoidea.

Reconnaissance of Surface Water Estrogenicity and the Prevalence of Intersex in Smallmouth Bass (Micropterus Dolomieu) Inhabiting New Jersey

The observation of testicular oocytes in male fishes has been utilized as a biomarker of estrogenic endocrine disruption. A reconnaissance project led in the Northeastern United States (US) during the period of 2008–2010 identified a high prevalence of intersex smallmouth bass on or near US Fish & Wildlife Service National Wildlife Refuges that included the observation of 100% prevalence in smallmouth bass males collected from the Wallkill River, NJ, USA. To better assess the prevalence of intersex smallmouth bass across the state of New Jersey, a tiered reconnaissance approach was initiated during the fall of 2016. Surface water samples were collected from 101 (85 river, 16 lake/reservoir) sites across the state at base-flow conditions for estrogenicity bioassay screening. Detectable estrogenicity was observed at 90% of the sites and 64% were above the US Environmental Protection Agency trigger level of 1 ng/L. Median surface water estrogenicity was 1.8 ng/L and a maximum of 6.9 ng/L E2Eq_BLYES was observed. Adult smallmouth bass were collected from nine sites, pre-spawn during the spring of 2017. Intersex was identified in fish at all sites, and the composite intersex prevalence was 93.8%. Prevalence across sites ranged from 70.6% to 100%. In addition to intersex, there was detectable plasma vitellogenin in males at all sites. Total estrogenicity in surface water was determined at these fish collection sites, and notable change over time was observed. Correlation analysis indicated significant positive correlations between land use (altered land; urban + agriculture) and surface water estrogenicity. There were no clear associations between land use and organismal metrics of estrogenic endocrine disruption (intersex or vitellogenin). This work establishes a baseline prevalence of intersex in male smallmouth bass in the state of New Jersey at a limited number of locations and identifies a number of waterbodies with estrogenic activity above an effects-based threshold.

The Degree of Sex Reversal in Muscovy Ducks (Cairina moschata domestica) Induced by an Aromatase Inhibitor

Under the same feeding conditions, the growth and development of male Muscovy ducks is significantly greater than that of females. Thus, controlling their sex expression can have economic benefits. However, reports on the degree of sex reversal in Muscovy ducks are scarce. In this study, we obtained sex-reversed Muscovy ducks by injecting letrozole before sex differentiation. We analyzed the degree of sex reversal in Muscovy ducks in terms of hormone levels, gonadal tissue development, and growth and found that the estradiol levels of AI-females (letrozole-induced female-to-male sex reversal) were not significantly different from those of normal males (p > 0.05), but the testosterone levels were significantly lower than those in normal males (p < 0.05). AI-female gonad tissue had changed, and the right gonad presented ovotestis tissue. The growth and development of AI-females was significantly less than that of normal males (p < 0.05) but was not significantly different from that of normal females (p > 0.05). Letrozole can induce female Muscovy ducks to convert into males, but the reversal cannot be completed. Thus, further studies are needed to elucidate how to entirely attain the change.

Gonad pathology and intersex severity in pelagic (Tilapia zilli) and benthic (Neochanna diversus and Clarias gariepinus) species from a pesticide-impacted agrarian catchment, south-south Nigeria

Pesticides are distributed to different degrees in surface water and sediment, thus, risks of toxicity and adverse impacts to physiology of resident species could be determined by their microhabitat (sub-habitat) associations, either water column or sediment. River Owan receives pesticide input from diffuse sources from adjacent farmlands. Surface water, sediment and fish samples [(Pelagic: Tilapia zilli (n = 92) and benthic: Neochanna diversus (n = 59), Clarias gariepinus (n = 68) were collected within the catchment area across seasons for 18-months (August 2016-January 2018) and measured for pesticide levels. Testicular and Ovarian tissue samples across the three species were also examined for pathological alterations. Individual pesticide concentrations in surface water and sediment exceeded international allowable limits, while concentration of pesticide residues in tissues of benthic species was higher compared to pelagic fish. Histopathological assessment revealed a higher incidence of ovarian disruption including atretic follicles, intersex and disorganization of ovarian structure in benthic (bottom-dwelling) fish (C. gariepinus and N. diversus) compared to pelagic (water-column) fish (T. zilli). Males benthic fish species also recorded more severe anomalies, compared to pelagic fish. The damages and anomalies observed in ovarian and testicular tissue indicate chronic responses to pollutant exposure, and implicates the elevation of pesticide concentrations in surface water and sediment above permissible limits. The higher incidence of anomalies recorded for benthic species compared to pelagic species, indicates greater risks of reproductive disruption and could be associated with the microhabitat preferences (water-column or sediment).

Feminization, altered gonadal development, and liver damage in least killifish (Heterandria formosa) exposed to sublethal concentrations of 17α-ethinylestradiol

The widespread use of the synthetic estrogen 17 α-ethinylestradiol (EE₂) has resulted in elevated levels in aquatic environments, where it is known to act as an endocrine disrupting chemical affecting fish and other aquatic organisms. Examining changes in the structure of the fish' gonads and liver has proven to be an effective approach for assessing these impacts. While changes have been reported for various fish species, it is not clear whether impacts are equally severe in live-bearing fishes. The present study looked at gonadal and liver development in EE₂-exposed least killifish (Heterandria formosa), a live-bearing Poeciliid. Exposures to 0, 5, or 25 ng/L EE₂ began within six days of birth and continued until fish became sexually mature 12-23 weeks later. Exposure to 5 ng/L EE₂ resulted in severe intersex in fish with external male characteristics, a slowdown of spermatogenesis in these intersex fish and a slowdown of oogenesis in the female fish. Moreover, these fish had a variety of liver injuries. Fish exposed to 25 ng/L EE₂ exhibited intersex but at a lower frequency than occurred at 5 ng/L. In contrast, liver damage and slowdown of both oogenesis and spermatogenesis exhibited the typical dose-dependence. These findings illustrate the importance of including histological analyses when assessing endocrine disruption in fish, demonstrate that the live-bearing mode of reproduction appears to provide limited protection from the effects of waterborne EE₂, and provide further evidence that EE₂ has multiple impacts on fish health and reproduction that are severe enough to potentially affect fish populations.

The intersex phenomenon in Sarotherodon melanotheron from Lagos lagoon (Nigeria): Occurrence and severity in relation to contaminants burden in sediment

The correlation between endocrine active contaminants in the environment and alterations in reproductive development of Sarotherodon melanotheron from Lagos lagoon has been investigated. Sediment and a total of 155 fish (74 males and 81 females) were collected between November 2014-March 2015 from selected contaminated sites (Ikorodu, Oworonshoki, Makoko and Idumota) and a putative control site (Igbore) along the lagoon. Sediment contaminant analysis revealed, significantly higher concentration of lindane, dieldrin, 4-iso-nonylphenol, 4-t-octylphenol and monobutyltin cation at the contaminated sites. Examination of gross morphological and histological changes of fish gonads showed a 27.4% prevalence of intersex in the sampled fish, of which 78% were males (testes-ova) and 22% were females (ovo-testis). Quantitative PCR (qPCR) of liver transcripts revealed the presence of vitellogenin (vtg) levels in male fish from contaminated sites. Zona radiata proteins (zrp) mRNA levels were significantly higher in females, compared to male fish. In general, significantly lower vtg and zrp transcripts levels were recorded at Igbore (control site), compared with contaminated sites. Principal component analysis (PCA) showed site and sex relationship in biological responses and contaminants, including trace metals, demonstrating that measured endocrine responses in fish were associated with contaminant burden in sediment. In addition, positive relationships were observed in male fish from Idumota, Oworonshoki and Ikorodu with vtg and dieldrin/4-iso-nonyphenol, with higher levels in male fish, compared to females. Further, contaminants from the Makoko, Oworonshoki and Ikorodu sites were positively associated with higher GSI and zrp in females. More importantly, the severity of intersex and changes in vtg transcripts imply a progressive feminization of male fish with concomitant alteration in the reproductive health of fish inhabiting the Lagos lagoon.

Temporal evaluation of estrogenic endocrine disruption markers in smallmouth bass (Micropterus dolomieu) reveals seasonal variability in intersex

A reconnaissance project completed in 2009 identified intersex and elevated plasma vitellogenin in male smallmouth bass inhabiting the Missisquoi River, VT. In an attempt to identify the presence and seasonality of putative endocrine disrupting chemicals or other factors associated with these observations, a comprehensive reevaluation was conducted between September 2012 and June 2014. Here, we collected smallmouth bass from three physically partitioned reaches along the river to measure biomarkers of estrogenic endocrine disruption in smallmouth bass. In addition, polar organic chemical integrative samples (POCIS) were deployed to identify specific chemicals associated with biological observations. We did not observe biological differences across reaches indicating the absence of clear point source contributions to the observation of intersex. Interestingly, intersex prevalence and severity decreased in a stepwise manner over the timespan of the project. Intersex decreased from 92.8% to 28.1%. The only significant predictor of intersex prevalence was year of capture, based on logistic regression analysis. The mixed model of fish length and year-of-capture best predicted intersex severity. Intersex severity was also significantly different across late summer and early spring collections indicating seasonal changes in this metric. Plasma vitellogenin and liver vitellogenin Aa transcript abundance in males did not indicate exposure to estrogenic endocrine disrupting chemicals at any of the four sample collections. Analysis of chemicals captured by the POCIS as well as results of screening discrete water samples or POCIS extracts did not indicate the contribution of appreciable estrogenic chemicals. It is possible that unreported changes in land-use activity have ameliorated the problem, and our observations indicate recovery. Regardless, this work clearly emphasizes that single, snap shot sampling for intersex may not yield representative data given that the manifestation of this condition within a population can change dramatically over time.

Indicators of exposure to estrogenic compounds at Great Lakes Areas of Concern: species and site comparisons

Adverse effects resulting from potential exposure of wild fishes to estrogenic endocrine disruptors were assessed at seven United States Great Lakes Areas of Concern using biomarkers ranging from organismal (gonadosomatic indices) to tissue/plasma (histology, plasma vitellogenin) and molecular (hepatic gene transcripts) levels. Biomonitoring was conducted on pelagic, top predator species, largemouth Micropterus salmoides and smallmouth M. dolomieu bass and benthic, omnivorous white sucker Catostomus commersonii. Seasonal (spring and fall) comparisons were conducted at select sites. Intersex (testicular oocytes), plasma vitellogenin, and hepatic vitellogenin transcripts were commonly observed in bass species. Testicular oocyte severity was positively, although weakly, correlated with plasma vitellogenin, hepatic transcripts of vitellogenin, estrogen receptor α, and estrogen receptor β2, while negatively correlated with androgen receptor β and phosphoenolpyruvate carboxykinase. No testicular oocytes were observed in white sucker; however, plasma vitellogenin and hepatic vitellogenin transcripts were commonly detected in the males. The results demonstrate the importance of utilizing multiple endpoints to assess exposure to estrogenic compounds as well as the importance of choosing sensitive species.

Modeling the exposure of wild fish to endocrine active chemicals: Potential linkages of total estrogenicity to field-observed intersex

Decades of studies on endocrine disruption have suggested the need to manage the release of key estrogens from municipal wastewater treatment plants (WWTP). However, the proposed thresholds are below the detection limits of most routine chemical analysis, thereby restricting the ability of watershed managers to assess the environmental exposure appropriately. In this study, we demonstrated the utility of a mechanistic model to address the data gaps on estrogen exposure. Concentrations of the prominent estrogenic contaminants in wastewaters (estrone, estradiol, and ethinylestradiol) were simulated in the Grand River in southern Ontario (Canada) for nine years, including a period when major WWTP upgrades occurred. The predicted concentrations expressed as total estrogenicity (E2 equivalent concentrations) were contrasted to a key estrogenic response (i.e., intersex) in rainbow darter (Etheostoma caeruleum), a wild sentinel fish species. A predicted total estrogenicity in the river of ≥10 ng/L E2 equivalents was associated with high intersex incidence and severity, whereas concentrations <0.1 ng/L E2 equivalents were associated with minimal intersex expression. Exposure to a predicted river concentration of 0.4 ng/L E2 equivalents, the environmental quality standard (EQS) proposed by the European Union for estradiol, was associated with 34% (95% CI:30-38) intersex incidence and a very low severity score of 0.6 (95% CI:0.5-0.7). This exposure is not predicted to cause adverse effects in rainbow darter. The analyses completed in this study were only based on the predicted presence of three major estrogens (E1, E2, EE2), so caution must be exercised when interpreting the results. Nevertheless, this study illustrates the use of models for exposure assessment, especially when measured data are not available.

Neurokinin B signaling in hermaphroditic species, a study of the orange-spotted grouper (Epinephelus coioides)

Neurokinin B (NKB) plays important roles in the mammalian reproductive axis by modulating the release of gonadotropin-releasing hormone (GnRH) and gonadotropins. In the present study, the tac3 cDNA was cloned from a hermaphroditic species, the orange-spotted grouper. Sequence analysis showed that the grouper Tac3 precursor encoded two tachykinin peptides, NKB and NKB-related peptide (NKBRP). Expression analysis in different tissues revealed that tac3 mRNA was highly expressed in the brain of the orange-spotted grouper. In situ hybridization further revealed that it was localized in some hypothalamic nuclei associated with reproductive regulation. During ovarian development, an increase of tac3 expression in the hypothalamus was observed at vitellogenesis stage. Intraperitoneal administration of NKB could increase the gnrh1 and lhβ mRNA levels, and enhance the serum estrogen levels, but did not significantly influence lhβ expression in cultured pituitary cells, indicating that NKB does not directly exert its actions on the pituitary gland. However, it was found that NKBRP had no effect on the expression of two gnrhs and two gths in vivo and in vitro. Effects of sex steroids on tac3 expression were further investigated. During the 17-methyltestosterone-induced sex change in the orange-spotted grouper, hypothalamic tac3 expression showed no significant change. Interestingly, ovariectomy greatly stimulated tac3 expression, while the 17β-estradiol treatment reversed this effect. In general, our data highly indicated that NKB signaling could activate the reproductive axis in the orange-spotted grouper. Our study is the first description of the NKB signaling in the hermaphroditic species.

First assessment of the effectiveness of the international convention on the control of harmful anti-fouling systems on ships in Tunisia using imposex in Hexaplex trunculus as biomarker

The global ban on the use of tributyltin (TBT) forced in September 2008 was ratified in Tunisia as late as June 2011. In this context, the present study aims to highlight the consequences of TBT contamination by monitoring 22 Tunisian sites before (2007) and after the ban (2012 and 2016) using as biomarker the occurrence of imposex in Hexaplex trunculus. From 2004 to 2016, complete recovery from imposex was reported in 11 sites. All average imposex indices calculated for each sampling year also decreased: imposex incidence from 61 to 27%, VDSI from 2 to 0.7, and RPLI from 15.7 to 1.6%. Ecological Quality Ratios (EQR) revealed that the sampling sites are in moderate to good ecological status. Overall, the present study confirms the effectiveness of the enacted legislation in reducing the impact of TBT pollution along the Tunisian coast.

Imposex in Nassarius nitidus (Jeffreys, 1867) as a possible investigative tool to monitor butyltin contamination according to the Water Framework Directive: A case study in the Venice Lagoon (Italy)

Butyltin (TBT, DBT, and MBT) effects on molluscs, especially endocrine disruption in bivalves and gastropods, have been widely investigated. Imposex, the superimposition of male characters onto female gonochoristic Caenogastropods, is the most studied biological effect of TBT. TBT compounds are among the priority hazardous substances within Directives 2000/60/EC (WFD) and 2008/105/EC. The Environmental Quality Standards (EQSs) set by the WFD for TBT are quite difficult to quantify by means of chemical analysis, without the use of expensive and high performance methods. Assuming that EQSs set for TBT were derived from evidence of imposex development at very low concentrations, this specific biomarker could be used as an indirect measure of assessing levels of bioavailable BTs. Therefore, this study aims to validate the use of imposex development as an investigative tool to monitor the bioavailable fraction of BTs within the WFD, by comparing imposex levels and BT concentrations in Nassarius nitidus from the Venice Lagoon. BT concentrations and imposex levels in N. nitidus, collected in 2013, had decreased when compared to previous studies in the same area. Both VDSI and RPLI correlated positively with BT body burden in females, confirming that imposex is a valid tool to monitor bioavailable BTs. However, TBT is still a matter of concern in the Venice Lagoon, as TBT concentrations were still higher than its degradation products suggesting recent fresh TBT inputs in the studied area. To propose imposex levels as an indicator of the impact of BTs within the WFD, classification class boundaries and Ecological Quality Ratios were introduced. As a preliminary attempt, imposex levels were also compared to the OSPAR Commission EcoQOs which linked imposex levels in Nassarius reticulatus with TBT concentrations in water. Based on this comparison the degree of imposex development in the Venice Lagoon suggested that TBT concentrations in water should be over the EQS-AA concentration and, at one site, also over the EQS-MAC. From all the results obtained in this work, it appears that imposex evaluation in N. reticulatus could give information about the ecological status regarding BT compounds under the WFD and also be used to monitor their effects and support chemical analyses until more sensitive methods become available.

Recovery of the New Zealand muricid dogwhelk Haustrum scobina from TBT-induced imposex

Levels of imposex in the muricid dogwhelk Haustrum scobina (Quoy & Gaimard, 1833) were assessed in two major New Zealand ports between 2015 and 2017, 12+years after the banning of TBT-based antifouling paints. In the 1990s imposex was common adjacent to port facilities and marinas in Waitemata and Tauranga Harbours, and several populations were found to be largely sterile and in decline. By 2015-17 imposex was largely absent from Tauranga Harbour and considerably reduced in Waitemata Harbour. In Waitemata Harbour imposex remained in areas adjacent to hull cleaning facilities and marinas, but at low levels and frequencies. These data highlight the success of the 2003 banning of TBT-based antifouling paints in reducing levels of imposex in New Zealand ports. However, these reductions in antifouling chemicals and subsequent population recoveries may have had unforseen effects within these harbours including changes in community structure and the arrival of non-indigenous species.

Imposex levels and butyltin compounds (BTs) in Hexaplex trunculus (Linnaeus, 1758) from the northern Adriatic Sea (Italy): Ecological risk assessment before and after the ban

The aim of this study was to compare imposex and butyltin compounds (BTs) data, collected before and after the organotin ban in 2008, in order to assess temporal and spatial variation of the phenomenon, the decline of BT contamination, and the effects on Hexaplex trunculus population in the coastal area of the northern Adriatic Sea, close to the Venice Lagoon. Both in marine and in lagoon sites, the results obtained in 2013-2015 showed a significant decline in the incidence of imposex in respect to those from the 2002 survey. In 2002, lagoon samples exhibited Relative Penis Size Index (RPSI) higher than marine samples, whereas no differences were detected in the recent survey, when all RPSI values were below 0.6%. Vas Deference Sequence Index (VDSI) mean values were over 4 before the ban introduction and below this value after that, indicating more critical conditions for gastropod population in 2002 rather than in 2013-15. Percentage of sterile females was up to 69% in 2002, whilst in the more recent survey no sterile female was found. Range of BT concentrations in gastropods decreased from 252 to 579 to 16-31ng∑BT/g d.w. BT body burdens varied according to a gender dependant pattern, with higher concentrations observed in females than in males. A first attempt to propose a classification based on BT impact on H. trunculus, according to the Water Framework Directive, revealed that most sites were in Bad ecological status before the ban and attained a Poor/Moderate status after that.

Estrogenic effects following larval exposure to the putative anti-estrogen, fulvestrant, in the fathead minnow (Pimephales promelas)

The objective of the present study was to investigate the consequences of early-life exposure to fulvestrant on estrogenic gene expression in fathead minnow larvae. To address this objective, fathead minnow larvae were exposed to fulvestrant (ICI 182,780) during the window of sexual differentiation between 0 to 30 days post-hatch (dph). The four treatment groups in this study included: filtered water controls (never exposed), solvent controls (ethanol 0.01%), and nominally low (0.10μg/L) and high (10.0μg/L) doses of fulvestrant. Following 30 d exposure to their respective treatment, larvae were transferred to filtered water aquaria and assessed for alterations in endocrine-responsive gene expression (i.e., RT-qPCR), body size and survival. The remaining fish depurated in filtered water until reaching sexual maturity (180dph) for assessment of persistent effects on sex characteristics, reproductive performance and sex ratio. Following the 30-d early life exposure, larvae showed upregulations of the endocrine-responsive genes ar, erβ and vtg in response to both low and high doses of fulvestrant, but showed no differences in survival or body mass. Upon reaching sexual maturity under depuration conditions, male minnows previously exposed to fulvestrant as larvae showed reductions in gonad mass along with the feminization of secondary sex characteristics with no observed effects in females. Exposure to fulvestrant had no effects on gonadal histology, reproductive performance or final sex ratio as adults. Results from this study demonstrate that aqueous exposure to fulvestrant is estrogenic in fathead minnow larvae and is capable of feminizing male fish as adults following early life exposure.

Extended imposex monitoring in N Atlantic Spain confirms punctual attainment of European environmental objectives for TBT

Legislation in the European Union (EU) aimed at reaching by 2015 a Good Ecological Status in regard to tributyltin (TBT, the biocide used in traditional antifouling paints). With a view to check such an achievement in N Atlantic Spain, baseline monitoring of gastropod imposex (the recommended assessment tool) was extended up to that date. In Galicia (the Western part of the study area) the use of the rock snail Nucella lapillus since 1996 had shown this environmental objective to be met as soon as 2009, but new surveys reveal no further improvement thereafter. As for the Eastern Cantabrian coast, imposex levels in the mud snail Nassarius reticulatus progressively declined from 2006 to 2015, when records finally complied with expectations. Both data sets are confronted and discussed in relation to the diverse environmental factors that may be determining the distribution of gastropods in these regions.

Androgen-induced pseudo-hermaphroditic phenotypes in female Brevimyrus niger Günther 1866 (Teleostei, Mormyridae)

This paper explores the plasticity of sexually dimorphic characters in subadult female Brevimyrus niger, an African weakly electric mormyrid species. Thirty-five fish were exposed in a staggered fashion (five fish a week) to aromatizable 17α-methyltestosterone over a period of 7 weeks; 18 fish served as untreated controls. 17α-MT induced precocious vitellogenesis that mirrored the natural maturational process during seasonal ovarian recrudescence. At the same time, 17α-MT exposure resulted in complete masculinization of the females' anal fin support structure normally observed during rainy season in adult males. We discuss possible hormonal mechanisms acting along the brain-pituitary-gonad axis that would explain the occurrence of precocious vitellogenesis and the male-typical transformation of the female's anal fin ray bases. Our findings are relevant to commercial aquaculture as the use of 17α-MT in fish hatcheries can pose serious environmental issues.

Tetrabromoethylcyclohexane affects gonadal differentiation and development in the frog Pelophylax nigromaculatus

Tetrabromoethylcyclohexane (TBECH), an additive brominated flame retardant, has been shown to have an androgenic activity in vitro. In the present study, we aimed to investigate the effects of TBECH on gonadal differentiation and development in the frog Pelophylax nigromaculatus, an amphibian species sensitive to androgenic chemicals, and to assess the androgenic activity of TBECH in vivo. P. nigromaculatus tadpoles were exposed to TBECH (1, 10, 100nM) from Gosner stage 24 to complete metamorphosis, and to 5α-dihydrotestosterone (DHT) as a positive control. We found that 1nM DHT resulted in 100% males, while the sex ratio in the solvent control group was close to 1:1. In all the TBECH treatment groups, sexually ambiguous gonads based on gross morphology and intersexualities with testicular and ovarian histological structures were found, but no abnormality occurred in the solvent control. In the 1, 10, 100nM TBECH treatment groups, the female percentages were 52%, 31%, 17%, with 36%, 56%, 66% for males and 12%, 13%, 17% for abnormal sexes, respectively. X²-test revealed significant differences in sex ratios between the three TBECH groups and the solvent control group, and the sex ratios in the two higher concentration groups were male-biased. These observations show that TBECH has a masculinizing effect on gonadal differentiation and development in P. nigromaculatus, suggesting an androgenic activity of TBECH in vivo. To our knowledge, this is the first study demonstrating that TBECH could induce gonadal masculinization in an animal, which raises new concerns for reproductive risk of TBECH exposure.

Recovery of marine Conus (Mollusca: Caenogastropoda) from imposex at Rottnest Island, Western Australia, over a quarter of a century

Imposex is a reproductive abnormality in which female snails begin to transform to males, but do not become functional. It was caused by tributyltin (TBT) used as an antifoulant in boat paints. Imposex was first recorded marine snails (Conus) (Mollusca: Caenogastropoda) at Rottnest Island, Western Australia, in January 1991, where 88% of individuals at the west end were affected. Most were at moderate Stages 3 and 4 on a scale of 0 (no affect) to 6 (death). TBT was banned on boats <25m long in late 1991 in WA. In 1996, imposex had declined to 69% of females with Stages 3 and 4 still the most common. By 2007 only 35% of females exhibited imposex; Stage 3 was the highest level recorded. TBT was below detection limits. TBT was banned on vessels >25m in September 2013. In February 2017 only 4% of Conus had imposex, at Stage 1.

Butyltin contamination in Northern Chilean coast: Is there a potential risk for consumers?

Imposex is the superimposition of non-functional male sex organs in gastropod females. This syndrome is a hormonal imbalance induced by tributyltin (TBT) which have been used in antifouling paints formulation. The present study aimed to perform an integrated environmental assessment of imposex and butyltin (BT) contamination using surface sediments and tissues of Thaisella chocolata (an edible gastropod) from northern Chile. The results showed imposex incidence in 11 out of 12 sites. In the most contaminated sites, which are areas under the influence of maritime activities, and also used for fishing and aquaculture, RPLI were over 60 and VDSI over 4 (high incidence of sterile females). Exceptionally high contamination levels and evidences of fresh inputs of tributyltin (TBT) were detected along the studied area. TBT levels above 300 and 90ngSng^-1, respectively, were recorded in sediments and edible gastropod tissues of 6 sites. Thus, a daily ingestion of 90 to 173g of T. chocolata foot (4 to 8 organisms) from the most contaminated sites will certainly lead to the consumption of BT exceeding the tolerable daily intake recommended by European Food Safety Authority. It is reasonable to consider that human risk is even higher if daily consumption of additional seafood is considered. Moreover, some contaminated sites were located within the marine reserve "Isla Grande Atacama", indicating that even marine protected areas are under the influence of TBT contamination. These findings suggest that current levels of TBT in the studied area are sufficient to induce harmful effects on the environment and constitutes a potential threat to seafood consumers. Thus, national regulatory actions toward environmental protection and food safety of local populations are still mandatory, even after 8years of the TBT global ban by IMO.

Alteration in molecular markers of oocyte development and intersex condition in mullets impacted by wastewater treatment plant effluents

Wastewater Treatment Plant (WWTP) discharges are an important source of endocrine disrupting chemicals (EDCs) into the aquatic environment. Fish populations inhabiting downstream of WWTP effluents show alterations in gonad and gamete development such as intersex condition, together with xenoestrogenic effects such as vitellogenin up-regulation. However, the molecular mechanisms participating in the development of intersex condition in fish are not elucidated. The aim of this study was to assess the impact of two WWTPs effluents (Gernika and Bilbao-Galindo situated in the South East Bay of Biscay) with different contaminant loads, in thicklip grey mullet (Chelon labrosus) populations inhabiting downstream, examining the presence and severity of intersex condition, during two seasons. Molecular markers of xenoestrogenicity and oocyte differentiation and development (vtgAa, cyp19a1a, cyp19a1b, cyp11b, foxl2, dmrt1 and gtf3a) were also studied. Intersex mullets were identified downstream of both WWTPs and vtgAa was upregulated in intersex and non intersex males. Sex dependent differential transcription levels of target genes were detected in mullets from Galindo. However, no such pattern was observed in mullets from Gernika, suggesting an attenuating effect over studied genes caused by a higher presence of EDCs in this site, as indicated by the elevated prevalence of intersex mullets in this population. In conclusion, no direct association between xenoestrogenic responses and intersex condition was established. Mullets from Gernika showed signs of severe EDC exposure compared to those from Galindo, as demonstrated by the higher prevalence of intersex males and the reduction in transcription profile differences between sexes of gametogenic gene markers.

Occurrence of intersex in wild freshwater fish in Slovenian rivers: a histological evaluation

The aim of this preliminary research was to establish if there are intersex occurrences in wild freshwater fish in Slovenian rivers and streams. In the first study we evaluated all fish species of both sexes obtained from the river Ljubljanica from its source to mouth. In the second study we focused on the rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta m. fario) males from 30 rivers and streams in different parts of Slovenia. The male gonads were histologically assessed for the presence of oocytes to determine the frequency and degree of intersex. Oocytes were found in the testicular tissue of a single grayling (Thymallus thymallus) and in the adipose tissue adjacent to the testis of a single common barbel (Barbus barbus), both from the Ljubljanica. Several cyst-like structures that resemble degenerated presumptive oocytes were also present in several trout testes. This preliminary report is the first of its kind in Slovenia. To gain a better insight into the intersex issue in Slovenia, we plan to regularly biomonitor freshwater pollution by histologically examining fish gonads and, if possible, by determining vitellogenin plasma levels in fish.

Endocrine active contaminants in aquatic systems and intersex in common sport fishes

Male fish are susceptible to developing intersex, a condition characterized by the presence of testicular oocytes. In the present study, the relationship between intersex and exposure to estrogenic endocrine active contaminants (EACs) was assessed for 2 genera of sport fish, Micropterus and Lepomis, at 20 riverine sites. Seasonal trends and relationships between EACs and intersex (prevalence and severity) were examined at varying putative sources of EACs throughout North Carolina, identified as point sources, nonpoint sources, and reference sites. Intersex was identified in both genera, which was documented for the first time in wild-caught Lepomis. Intersex was more prevalent (59.8%) and more severe (1.6 mean rank) in Micropterus, which was highly correlation to EACs in sediment. In contrast, intersex was less common (9.9%) and less severe (0.2 mean rank) in Lepomis and was highly correlated to EACs in the water column. The authors found that concentrations of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, industrial EACs, and estrogens were highest at point source sites; however, no source type variation was identified in the prevalence or severity of intersex, nor were there seasonal trends in intersex or EAC concentrations. The authors' results associate genus-specific prevalence of intersex with specific EAC classes in common sport fishes having biological, ecological, and conservation implications. Environ Toxicol Chem 2017;36:959-968. © 2016 SETAC.

Reduction of Intersex in a Wild Fish Population in Response to Major Municipal Wastewater Treatment Plant Upgrades

Intersex in fish downstream of municipal wastewater treatment plants (MWWTPs) is a global concern. Consistent high rates of intersex in male rainbow darter (Etheostoma caeruleum) have been reported for several years in the Grand River, in southern Ontario, Canada, in close proximity to two MWWTPs. The larger MWWTP (Kitchener) recently underwent upgrades that included the conversion from a carbonaceous activated sludge to nitrifying activated sludge treatment process. This created a unique opportunity to assess whether upgrades designed to improve effluent quality could also remediate the intersex previously observed in wild fish. Multiple years (2007-2012) of intersex data on male rainbow darter collected before the upgrades at sites associated with the MWWTP outfall were compared with intersex data collected in postupgrade years (2013-2015). These upgrades resulted in a reduction from 70 to 100% intersex incidence (preupgrade) to <10% in postupgrade years. Although the cause of intersex remains unknown, indicators of effluent quality including nutrients, pharmaceuticals, and estrogenicity improved in the effluent after the upgrades. This study demonstrated that investment in MWWTP upgrades improved effluent quality and was associated with an immediate change in biological responses in the receiving environment. This is an important finding considering the tremendous cost of wastewater infrastructure.

Bi-species imposex monitoring in Galicia (NW Spain) shows contrasting achievement of the OSPAR Ecological Quality Objective for TBT

Imposex is decreasing worldwide after the total ban on tributyltin (TBT) from antifouling paints. In order to assess improvement in the NE Atlantic, the OSPAR Convention designed an Ecological Quality Objective (EcoQO) based on the VDSI (vas deferens sequence index, an agreed measure of imposex) in the rock snail Nucella lapillus; wherever this is not available, the mud snail Nassarius reticulatus was proposed as a proxy. We determined VDSI in Galician populations of rock (n≥34) and mud (n≥18) snails at regular intervals from pre-ban times until 2009 and 2011, respectively. While imposex in the former started decreasing in 2006 and by 2009 the EcoQO had been met in the area, VDSI in the latter was not significantly reduced until 2011 and values contradict such an achievement. This suggests that the OSPAR imposex bi-species scheme may not be of direct application in the current post-ban scenario.

No evidence of exposure to environmental estrogens in two feral fish species sampled from the Yarra River, Australia: A comparison with Northern Hemisphere studies

Environmental estrogens originate from a variety of sources including sewage treatment plant (STP) effluents and adverse physiological effects (endocrine disruption) have been observed in several fish species sampled downstream of STP discharges. In this study we examined common carp (Cyprinus carpio) and roach (Rutilis rutilis) for signs of exposure to environmental estrogens in the iconic Yarra River, Melbourne, Australia. The Yarra River flows through the city of Melbourne and more than 2 million people live within the catchment. Two STPs discharge water into the Yarra River within the middle reaches, and the areas immediately downstream of these discharge locations were the focus of this study. Carp and roach were chosen as test species since both have been utilised extensively for endocrine disruption research throughout Europe, North America and Asia, and data from various international studies was used for comparison with the results of the present study. Neither species showed evidence of exposure to environmental estrogens, with no elevation of plasma vitellogenin levels in males and no incidence of intersex gonads. Most physiological endpoints in both species from this study were within ranges reported in carp and roach from reference sites in other studies, however some degenerative histological changes in both male and female gonads were observed. Surface water samples showed no estrogenic activity (measured by the yeast-estrogen screen, YES), but did display strong anti-estrogenic and weak androgenic activity (measured by the yeast-androgen screen, YAS). Whilst the results show no evidence of impacts from environmental estrogens in the Yarra River, the presence of both anti-estrogenic and androgenic activity in water samples, as well as some gonadal changes in carp is concerning and indicates that our focus needs to broaden, in order to look for biological impacts in resident fauna that might be due to environmental pollutants other than environmental estrogens.

Spatiotemporal appraisal of TBT contamination and imposex along a tropical bay (Todos os Santos Bay, Brazil)

A spatiotemporal evaluation of butyltin contamination was performed between 2010 and 2012 along Todos os Santos Bay (Northeast Brazil) using surface sediments, bivalve tissues (Anomalocardia brasiliana and Mytella guyanensis), and imposex occurrence (Stramonita rustica). The spatial study detected high tributyltin (TBT) levels (maximum values of 262 ng Sn g (-1) - 21,833 ng Sn g(-1) of total organic carbon - for surface sediments and 421 ng Sn g(-1) for bivalve tissues) in the innermost part of the bay. The TBT levels detected in M. guyanensis tissues might cause human health risk since local population consumes these organisms. These high concentrations observed in the bivalves might result in ingestions higher than the safe limits established by European Food Safety Authority (250 ng TBT kg(-1) day(-1)). Considering the temporal evaluation, no difference (p > 0.05) was observed between TBT concentrations in sediments obtained during the two sampling campaigns (2010/2011 and 2012). However, the increasing predominance of TBT metabolites (butyltin degradation index (BDI) >1) in more recent sediments indicates further degradation of old TBT inputs. In spite of that, recent inputs are still evident at this region. Nevertheless, a reduction of imposex parameters in S. rustica over the last decade suggests an overall decline in the TBT contamination, at least in the outermost and possible less impacted region of the bay. The TBT contamination is probably reducing due to the national and international legislative restrictions on the use of TBT as antifouling biocide. The contamination levels, however, are still relevant especially in the inner part of Todos os Santos Bay since they are above those that are likely to cause toxicity to the biota.

Endocrine-disruptor molecular responses, occurrence of intersex and gonado-histopathological changes in tilapia species from a tropical freshwater dam (Awba Dam) in Ibadan, Nigeria

In the present study, the occurrence of endocrine disruptive responses in Tilapia species from Awba Dam has been investigated, and compared to a reference site (Modete Dam). The Awba Dam is a recipient of effluents from University of Ibadan (Nigeria) and several other anthropogenic sources. A total of 132 Tilapia species (Sarotherodon malenotheron (n=57 and 32, males and females, respectively) and Tilapia guineensis (n=23 and 20, males and females, respectively)) were collected from June to September 2014. At the reference site, samples of adult male and female S. melanotheron (48 males and 47 females) and T. guineensis (84 males and 27 females) were collected. Gonads were morphologically and histologically examined and gonadosomatic index (GSI) was calculated. Hepatic mRNA transcriptions of vitellogenin (Vtg) and zona radiata protein (Zrp) genes were analyzed using validated RT-qPCR. Significant increase in Vtg and Zrp transcripts were observed in male tilapias from Awba Dam, compared to males from the reference site. In addition, male tilapias from Awba Dam produced significantly higher Vtg and Zrp mRNA, compared to females in June and July. However, at the natural peak spawning period in August and September, females produced, significantly higher Vtg and Zrp mRNA, compared to males. Fish gonads revealed varying incidence of intersex with a striking presence of two (2) pairs of testes and a pair of ovary in S. melanotheron from Awba Dam. The entire fish population examined at Awba Dam showed a high prevalence of intersex (34.8%), involving phenotypic males and females of both species. Analysis of sediment contaminant levels revealed that As, Cd, Pb, Hg and Ni (heavy metals), monobutyltin cation, 4-iso-nonyphenol and PCB congeners (138, 153 and 180) were significantly higher in Awba Dam, compared to the reference site. Principal component analysis (PCA) showed that fish variables were positively correlated with sediment contaminant burden at Awba Dam, indicating that the observed endocrine disruptive responses are associated with contaminant concentrations. Overall, the occurrence of intersex and elevated expressions of Vtg and Zrp in male fish, suggest that the measured contaminants were eliciting severe endocrine disruptive effects in Awba Dam biota, which is an important source of domestic water supply and fisheries for the University of Ibadan community.

p,p'-DDE Induces Gonadal Intersex in Japanese Medaka (Oryzias latipes) at Environmentally Relevant Concentrations: Comparison with o,p'-DDT

Previous studies have reported high body burdens of dichlorodiphenyltrichloroethane (DDT) and its metabolites in wild fishes worldwide. This study evaluated the adverse effects of 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE) and o,p'-DDT on gonadal development and reproduction by exposing transgenic Japanese medaka (Oryzias latipes) from hatch for 100 days. While both p,p'-DDE and o,p'-DDT induced intersex in male medaka, the lowest observable effective concentration (LOEC) of o,p'-DDT was 57.7 ng/g ww, about 5-fold lower than that (272 ng/g ww) of p,p'-DDE. Since LOECs of both chemicals were comparable to the body concentrations in wild fish, DDT contamination would likely contribute to the occurrence of intersex observed in wild fish. Exposure to o,p'-DDT resulted in much higher expression of vitellogenin in liver of males than p,p'-DDE, accordant with the higher potency of o,p'-DDT than p,p'-DDE to induce intersex. This phenomenon could be partly explained by the significantly elevated levels of 17β-estradiol in plasma of males exposed to o,p'-DDT, in addition to its estrogenic activity via the estrogen receptor. Significantly lower fertilization (p = 0.006) and hatchability (p = 0.019) were observed in the 13 intersex males. This study for the first time demonstrated the induction of intersex and reproductive effects of p,p'-DDE and o,p'-DDT at environmentally relevant concentrations.

Imposex in the dogwhelk (Nucella lapillus): 22-year monitoring around England and Wales

Six imposex surveys in the dogwhelk (Nucella lapillus) have been conducted over the past two decades to assess legislation effectiveness controlling the use of tri-butyl tin (TBT) by the maritime shipping industry. This study firstly analysed the results of the 2014 survey and secondly carried out a trend assessment of the same 88 sampled sites between 1997 and 2014 of which 65 showed statistically significant reductions. To highlight the magnitude of change, the Vas Deferens Sequence stages (VDS) of the same 56 sites sampled in 1997 and 2010 showed that the Vas Deferens Sequence Index (VDSI) reduced statistically significantly from 2.89 and 0.42, respectively. These data confirm that the legislation enacted, latterly through the International Maritime Organization (IMO) during 2003 to 2008, has been effective in progressively reducing the impact of TBT in the marine environment. Nevertheless, the 2014 results show that two of 18 sampled sites (Gurnard Bay and St. Mawes) are still above the Ecotoxicological Assessment Criteria (EAC) derived for TBT (VDSI ≤ 2).

Emerging wastewater contaminant metformin causes intersex and reduced fecundity in fish

The occurrence of intersex fish, where male reproductive tissues show evidence of feminization, have been found in freshwater systems around the world, indicating the potential for significant endocrine disruption across species in the ecosystem. Estrogens from birth control medications in wastewater treatment plant effluent have been cited as the likely cause, but research has shown that endocrine disruption is not solely predictable based on hormone receptor interactions. Many other non-hormone pharmaceuticals are found in effluent at concentrations orders of magnitude higher than estrogens, yet there is little data indicating the impacts of these other medications. The widely prescribed anti-diabetic metformin is among the most abundant of pharmaceuticals found in effluent and is structurally dissimilar from hormones. However, we show here that exposing fathead minnows (Pimephales promelas) to a concentration of metformin found in wastewater effluent causes the development of intersex gonads in males, reduced size of treated male fish, and reduction in fecundity for treated pairs. Our results demonstrate that metformin acts as an endocrine disruptor at environmentally relevant concentrations.

Estrogenicity and intersex in juvenile rainbow trout (Oncorhynchus mykiss) exposed to Pine/Eucalyptus pulp and paper production effluent in Chile

Pulp and paper mill effluents (PPMEs) have been shown to increase gonad size, cause early maturation, and disrupt hormone functions in native and non-native Chilean fish. In this study, we assessed reproductive (plasma vitellogenin; VTG, gonad development) and metabolic (ethoxyresorufin-O-deethylase activity; EROD) end points, relative liver size (LSI) and condition factor (K) of juvenile female and male rainbow trout exposed to effluents. Unlike previous studies, which have focus either on the specific effects of effluent on fish in laboratory exposures or biotic population statuses downstream of discharge sites, we simultaneously assessed the impacts of PPMES on trout using two approaches: (1) laboratory exposures of tertiary treated PPME produced from processing Eucalyptus globulus or Pinus radiata; and (2) in situ bioassay downstream of the combined discharge of the same pulp mill. Despite an increase in the average gonadosomatic index (GSI) in exposed fish, no statistical differences in gonad size between exposed and unexposed individuals was detected. However, both female and male fish exposed to effluents showed significantly higher concentrations of plasma VTG, so more in fish exposed to Eucalyptus-based effluent when compared to Pinus PPME. In addition, male fish showed intersex characteristics in all exposure assays (Eucaliptus and Pinus) and, despite the low concentration of effluent in the river (<1% [v/v]), similar responses were observed in the caged fish. Finally, EROD activity was induced in both in situ exposures and laboratory assays at the higher PPME concentration (60-85% PPME). This study confirms estrogenic effects in Chilean fish exposed to PPME and the necessity for biological effects monitoring in addition to the assessment of physical-chemical endpoints as required in current government regulations.

Effects of 17α-Methyltestosterone and Aromatase Inhibitor Letrozole on Sex Reversal, Gonadal Structure, and Growth in Yellow Catfish Pelteobagrus fulvidraco

Monosex populations are in demand in many fish species with sexual dimorphism, e.g., better growth performance, higher gonad value, superior ornamental value. From the point of view of research, a monosex population is one of the best materials for investigating sex-determining mechanisms, sex differentiation, and sex-linked markers. Sex reversal of females (phenotypic reversal from XX female to XX male) is the first step in all-female production in species with an XX/XY system for sex determination. In the present study, masculinization of yellow catfish, a species with XX/XY sex determination, was investigated by oral administration of various doses of 17α-methyltestosterone (MT) or an aromatase inhibitor (AI) letrozole (LZ); effects on survival, growth performance, sex ratio, and changes in gonadal structure were evaluated. Three doses (20, 50, and 100 mg kg(-1) diet) of oral MT or LZ were administered to fry from 10 days post-hatching (DPH) to 59 DPH. Oral administration of MT at all doses did not significantly change the ratio of males (45.8%, 33.3%, and 50.0% respectively) compared to the control group (37.5%), while yielding intersex fish at all doses (4.2% to 8.3%). Oral administration of LZ produced a significantly higher proportion of males in all doses (75.5%, 83.3%, and 75.0%, respectively). Additionally, the lowest dose of LZ improved the growth of treated fish compared to the control, and all doses of LZ enhanced spermatogenesis in treated males.

Environmental concentrations of anti-androgenic pharmaceuticals do not impact sexual disruption in fish alone or in combination with steroid oestrogens

Sexual disruption in wild fish has been linked to the contamination of river systems with steroid oestrogens, including the pharmaceutical 17α-ethinylestradiol, originating from domestic wastewaters. As analytical chemistry has advanced, more compounds derived from the human use of pharmaceuticals have been identified in the environment and questions have arisen as to whether these additional pharmaceuticals may also impact sexual disruption in fish. Indeed, pharmaceutical anti-androgens have been shown to induce such effects under laboratory conditions. These are of particular interest since anti-androgenic biological activity has been identified in the aquatic environment and is potentially implicated in sexual disruption alone and in combination with steroid oestrogens. Consequently, predictive modelling was employed to determine the concentrations of two anti-androgenic human pharmaceuticals, bicalutamide and cyproterone acetate, in UK sewage effluents and river catchments and their combined impacts on sexual disruption were then assessed in two fish models. Crucially, fish were also exposed to the anti-androgens in combination with steroid oestrogens to determine whether they had any additional impact on oestrogen induced feminisation. Modelling predicted that the anti-androgenic pharmaceuticals were likely to be widespread in UK river catchments. However, their concentrations were not sufficient to induce significant responses in plasma vitellogenin concentrations, secondary sexual characteristics or gross indices in male fathead minnow or intersex in Japanese medaka alone or in combination with steroid oestrogens. However, environmentally relevant mixtures of oestrone, 17β-oestradiol and 17α-ethinylestradiol did induce vitellogenin and intersex, supporting their role in sexual disruption in wild fish populations. Unexpectedly, a male dominated sex ratio (100% in controls) was induced in medaka and the potential cause and implications are briefly discussed, highlighting the potential of non-chemical modes of action on this endpoint.

Severe intersex is predictive of poor fertilization success in populations of rainbow darter (Etheostoma caeruleum)

Municipal wastewater effluent (MWWE) contains emerging contaminants such as pharmaceuticals and personal care products (PPCPs) that have estrogenic properties. PPCPs are thought to be responsible for feminization of male fish in heavily urbanized areas around the globe. While many observations of feminized male fish have been made, the impact of feminization on reproductive success is not well understood. To address this lack of knowledge of the impacts of feminization, we examined the reproductive fitness of rainbow darter (Etheostoma caeruleum), a fish that is also known to have been feminized in some reaches of the Grand River, Kitchener-Waterloo, Ontario, Canada. In order to assess their reproductive health, somatic indices, gonadal steroid production, fecundity, and histological severity of intersex were measured in male rainbow darter collected through an urban gradient. Reproductive fitness was assessed by stripping milt and eggs from wild spawning fish, fertilizing eggs manually, and rearing embryos to hatch. The fertilization success and survival of embryos to hatch were compared among sites. In this study, it was found that rainbow darter collected at sites near a large municipal wastewater treatment plant (MWWTP) had decreased gonad size, increased severity of intersex, and decreased androgen production relative to other sites. Fish collected near the largest MWWTP also had lower fertilization success and survival to hatch. In contrast, fish collected near a second MWWTP farther upstream had comparable fertilization success, but lower survival to hatch relative to the upstream rural reference site. Intersex severity was negatively correlated with fertilization success, but not survival to hatch, suggesting that intersex is a good indicator of a population's fertilization success. Further investigation is required in order to determine if feminization will impact the sustainability of wild populations of fish.

Gonadal disorder in the thinlip grey mullet (Liza ramada, Risso 1827) as a biomarker of environmental stress in surface waters

The aim of this study was to evaluate the use of gonadal alterations in the thinlip grey mullet (Liza ramada) as a biological indicator in assessing aquatic ecosystems health, with particular emphasis to river ecosystems exposed to sewage discharges. For this purpose, the reproductive status and the presence of gonadal alterations were studied in 206 mullets collected from two sites on the low course of the Tiber River, downstream of a large urban sewage treatment plant and in the estuarine area, and from an uncontaminated pond considered as reference site. Intersex and irregularly shaped gonads were observed in 20.8% of the mullets from the most polluted site, and intersex gonads in 10.3% of those from the estuarine area. No alterations were detected in the fish from the reference site, which also showed distinct stages of gonadal development. Conversely, unclear stages of testicular and ovary development were observed in the fish from the two polluted river sites. The results of this study suggest that L. ramada may represent a sentinel species in environmental risk assessment and support the use of gonadal alterations of this species as a bioindicator for extensive monitoring of pollution in lower stretches of rivers and estuarine areas.

Phenolic endocrine-disrupting chemicals and intersex in wild crucian carp from Hun River, China

This study investigated the concentrations of phenolic endocrine-disrupting chemicals (EDCs) and the incidence of ovo-testis (intersex) in wild crucian carp (Carassius carassius) sampled from the Hun River. As expected, nonylphenols (NP) and bisphenol A (BPA) were detected in all samples, and octylphenols (OP) were found in most samples. NP concentrations ranged from 1290 ± 584 to 3111 ± 2071 ng g(-1) wet weight (ww) in July and from 1132 ± 644 to 1556 ± 587 ng g(-1) ww in November; OP ranged from 6 ± 7 to 46 ± 38 ng g(-1) ww in July and from no detection to 22 ± 16 ng g(-1) ww in November; and BPA ranged from 4 ± 9 to 41 ± 24 ng g(-1) ww in July and from 6 ± 5 to 59 ± 24 ng g(-1) ww in November. Moreover, the concentrations of these compounds were higher in fish found down-stream of the sewage treatment plant (STP), and the lowest concentrations were found in fish up-stream of the STP. Concentrations of these EDCs in muscles might be correlated with the prevalence of intersex traits in wild fish, suggesting that these compounds contribute, at least in part, to the occurrence of intersex morphology. Thus, phenolic EDCs discharged from the STP pose a risk to the aquatic ecosystem in the Hun River.

Whole organism responses and intersex severity in rainbow darter (Etheostoma caeruleum) following exposures to municipal wastewater in the Grand River basin, ON, Canada. Part A

Municipal wastewater effluents (MWWEs) contain anthropogenic substances that can exhibit endocrine-disrupting activity. These complex mixtures have been observed to exert adverse effects on fish. Rainbow darter (Etheostoma caeruleum, RBD) is a small benthic fish that is widespread throughout the Grand River, Ontario, Canada, and has been previously shown to be adversely affected by MWWE exposure in this watershed. The objectives of this study were to quantify biological responses in this sentinel species and intersex severity in male fish, in relation to the area of urbanization. It focused on RBD populations adjacent to wastewater outfalls in the Grand River watershed. In May 2011, nine sites across the urban gradient were selected to evaluate the impact of MWWEs. Endpoints for energy storage (i.e. condition factor, k; liversomatic index, LSI) as well as reproductive endpoints (i.e. gonadosomatic index, GSI; gonad development, hormone production), and intersex were assessed in the fish. Rainbow darter showed a high incidence of intersex downstream of the wastewater outfalls, especially below the largest treatment plant outfall at Kitchener (∼85%). We applied an intersex index (score from 0 to 7) that considers the number of eggs within the testis and the stage of maturation of the egg. RBD exposed downstream of the largest wastewater outfall at Kitchener had a score of 3.81±0.37 compared to upstream to the urban areas where there were no intersex males found other than a single individual with a score 1 (average intersex score of site 0.06±0.06). In addition, several fish associated with the Kitchener outfall had macroscopic vitellogenic eggs in the testes (intersex scores 5 and 6). The sub-population of fish located at the wastewater outfall also showed a tendency towards skewed sex ratios (greater proportion of females to male fish) compared to the population at the reference sites. Male fish inhabiting the urbanized area of the Grand River also showed reduced levels of testosterone (T) and 11-ketotestosterone (11KT). Intersex males had the lower levels of 11KT relative to the upstream reference fish but could not be distinguished from normal males collected at the exposed sites. Despite the high levels of intersex at these sites, no relationships were evident among intersex severity and other measured endpoints such as GSI, LSI or in vitro steroid production. The effects observed appear to be associated with urbanization and exposure to treated MWWEs in the watershed. Although intersex incidence and severity was a very good indicator of wastewater exposure, intersex could not be directly linked to other effects in this wild population. The effects of MWWEs on transcriptional changes in adult RBD exposed to the effluents are reported in the corresponding report (Part B).

Molecular pathways associated with the intersex condition in rainbow darter (Etheostoma caeruleum) following exposures to municipal wastewater in the Grand River basin, ON, Canada. Part B

Rainbow darter (Etheostoma caeruleum; RBD) is a small benthic fish found in North America. This species is sensitive to sewage effluent, and intersex is found in up to 80% of males in near-field areas in the Grand River, Ontario, Canada. To learn more about the molecular signaling cascades associated with intersex, a developed customized oligonucleotide microarray (4×180 K) using next generation sequencing was developed to characterize the transcriptome in the gonad of male and female RBD. Gene expression profiling was performed in males and females from both a reference site and a polluted site. Males with and without intersex condition from the areas closest to effluent outfalls were compared to males and females from a reference site. Microarray analysis revealed that there was increased mRNA abundance for genes associated with oogenesis in intersex males (i.e. the presence of eggs within the testis), and a decrease in mRNA abundance for genes associated with spermatid development. In females exposed to effluent, cell processes related with hatching and ovulation were down-regulated, and genes involved in immune responses were increased in abundance. In the non-intersex males exposed to effluent, cell processes such as sperm cell adhesion were decreased at the transcript level relative to males from the reference site. Microarray analysis revealed that heat shock proteins (HSP) were significantly increased in non-intersex males exposed to effluent; however, HSPs were not differentially expressed in intersex males exposed to the effluent. Genes involved in sex differentiation (sox9, foxl2 and dmrt1) and reproduction (esr1, esrb, ar, vtg, cyp19a1 and cyp11a) were measured in males, females, and intersex individuals. Consistent with the intersex condition, many transcripts showed an intermediate expression level in intersex males when compared to phenotypic males and females. This study improves our knowledge regarding the molecular pathways that underlie the intersex condition and develops a suite of qPCR bioassays in RBD that are able to discriminate pollutant-exposed males without intersex from those males with intersex. Part A of this study reports on the effects of municipal wastewater effluents (MWWEs) on RBD in the Grand River and demonstrates that there are disruptions in higher level endpoints that include altered steroid levels. Here we develop a new tool for assessing and monitoring the intersex condition in RBD in polluted natural environments and begin to characterize gene networks that are associated with the condition.

Study on a new mechanism of sterilization in imposex affected females of tropical marine neogastropod, Thais sp

The morphological expressions and histopathological analysis of the gonads of a tropical marine neogastropod species (Thais sp.) from East Malaysia revealed new evidence of mechanical sterility in the imposex affected females. The gradual development of imposex was classified into five stages (Stage 0 to Stage 4) with three types of sterility conditions; Type A caused prohibition of copulation and capsule formation; Type B prohibits the releasing process of eggs; and gonads in Type C are infertile. Further analysis is needed to confirm, if the gonad malformation in imposex affected snails is generated specifically by tributyltin (TBT) or by other possible factors. The levels of imposex incidence (stages and percentages) were greater in a marina and decreased with increasing distance from the marina. Organotin tissue burden across the sexes showed that dibutyltin (DBT) as well as TBT might be the elements inducing imposex in Thais sp. from Miri in East Malaysia.

Intersex occurrence in rainbow trout (Oncorhynchus mykiss) male fry chronically exposed to ethynylestradiol

This study aimed to investigate the male-to-female morphological and physiological transdifferentiation process in rainbow trout (Oncorhynchus mykiss) exposed to exogenous estrogens. The first objective was to elucidate whether trout develop intersex gonads under exposure to low levels of estrogen. To this end, the gonads of an all-male population of fry exposed chronically (from 60 to 136 days post fertilization – dpf) to several doses (from environmentally relevant 0.01 µg/L to supra-environmental levels: 0.1, 1 and 10 µg/L) of the potent synthetic estrogen ethynylestradiol (EE2) were examined histologically. The morphological evaluations were underpinned by the analysis of gonad steroid (testosterone, estradiol and 11-ketotestosterone) levels and of brain and gonad gene expression, including estrogen-responsive genes and genes involved in sex differentiation in (gonads: cyp19a1a, ER isoforms, vtg, dmrt1, sox9a2; sdY; cyp11b; brain: cyp19a1b, ER isoforms). Intersex gonads were observed from the first concentration used (0.01 µg EE2/L) and sexual inversion could be detected from 0.1 µg EE2/L. This was accompanied by a linear decrease in 11-KT levels, whereas no effect on E2 and T levels was observed. Q-PCR results from the gonads showed downregulation of testicular markers (dmrt1, sox9a2; sdY; cyp11b) with increasing EE2 exposure concentrations, and upregulation of the female vtg gene. No evidence was found for a direct involvement of aromatase in the sex conversion process. The results from this study provide evidence that gonads of male trout respond to estrogen exposure by intersex formation and, with increasing concentration, by morphological and physiological conversion to phenotypic ovaries. However, supra-environmental estrogen concentrations are needed to induce these changes.

A persistent organic pollutant related with unusual high frequency of hermaphroditism in the neotropical anuran Physalaemus cuvieri Fitzinger, 1826

Representing a reflection of anthropic activity, the level of xenobiotic compounds in aquatic ecosystems has increased in recent years, bringing severe damage to the environment. The present work reports the occurrence of malformation in gonads of Physalaemus cuvieri individuals from a population of Atlantic Forest in Southern Brazil. Twenty male specimens were collected, which had their testicles removed, immersed in Karnovsky fixative solution, included in historesin for 2 μm cuts and stained with Hematoxylin-eosin. Four specimens showed intersexual gonads condition along with the presence of sperm and oocytes. In order to test a possible contamination of water, 2L were collected from the water body to check organochlorine, organophosphate and carbamate compounds. The analysis of water showed the presence of agrotoxic Dieldrin in a concentration of 0.05 μg/L, representing a concentration above the recommended reference. This agrotoxic, in addition to acting as endocrine disrupter and commercially prohibited, has quite persistent residual effects, and may be responsible for the high frequency of P. cuvieri with intersexual gonads, which in the long term can represent a risk for this population due to the potential impact on its effective reproductive ability.

Intersex condition and molecular markers of endocrine disruption in relation with burdens of emerging pollutants in thicklip grey mullets (Chelon labrosus) from Basque estuaries (South-East Bay of Biscay)

Endocrine disrupting chemicals (EDCs) interfere with the functioning of the endocrine system, causing reproductive and developmental disturbances in aquatic wildlife. Appearance of intersex gonads and elevated plasma levels of vitellogenin in male fish are well known biomarkers of exposure to xenoestrogenic EDCs. In the present study, intersex condition and transcription levels of vtg and cyp19a1b were assessed in five thicklip grey mullet populations from the Basque coast (Bay of Biscay). Levels of EDCs (estrogenic hormones, polycyclic musks, bisphenol-A, phthalates, alkylphenols and pesticides) were determined in water and fish bile. Intersex gonads were observed in three out of five mullet populations. Vtg and cyp19a1b were up-regulated in mullet populations with relatively higher EDCs load. Phthalates and pesticides were the most abundant EDCs in bile, followed by alkylphenols, musks, bisphenol-A and estrogenic hormones. Statistically significant correlations were found between concentrations of individual and total EDCs in bile and water samples and transcription levels of vtg and cyp19a1b.

Development of reproductive organs in the ivory shell Babylonia japonica: observations from wild populations and laboratory-reared juveniles

We histologically examined normal differentiation and development of genital tract and gonad in the ivory shell Babylonia japonica (Buccinidae) to determine whether the formation of male-type genitalia in imposex-exhibiting females mimics the normal development of male genitalia in prosobranch gastropods. We used a wild-caught 2-year-old specimen and laboratory-reared juveniles aged 0-24 months. Gonad differentiation was unclear before age 14 months, but progressed after 16 months. Both sexes had complete genital tract and mature gonad at 20 months. However, differentiation and development occurred earlier in females than in males. Development of genital tract preceded gonad differentiation. Vas deferens morphogenesis in males resembled that in imposex-exhibiting females. These findings help to understand the morphogenesis of genital tract and gonad in prosobranch gastropods and will contribute to more in-depth studies of the mode of action of organotin compounds such as TBT and TPhT in imposex development in female prosobranch gastropods.

Imposex development in Hexaplex trunculus (Gastropoda: Caenogastropoda) involves changes in the transcription levels of the retinoid X receptor (RXR)

In order to further demonstrate that TBT-induced imposex through RXR signaling is not species-specific, Hexaplex trunculus was selected as an experimental model species. We first isolated RXR in H. trunculus, and determined gene transcription through quantitative real-time PCR in key tissues (e.g., penis/penis-forming area and central nervous system:- CNS), upon exposure to tributyltin (TBT) (5 and 50 ng TBTL(-1)). Two months of exposure to TBT induced imposex and led to a significant increase in the severity of the phenomenon in females and an increase in male penis lengths. Exposure to TBT altered RXR gene transcription in a tissue and sex-specific manner. In the CNS, there were no significant changes in RXR gene transcription between control and TBT-exposed females. A similar trend was observed in male CNS. On the contrary, in the penis-forming area/penis of females exposed to TBT, a significant increase in RXR gene transcription was observed in the 50 ng TBTL(-1) group. Furthermore, a positive correlation was observed between overall female penis lengths and RXR gene transcription. In males, although a trend towards an increase in RXR gene transcription in penis was observed, differences did not reach significance. Overall, the results of the present study give further support to a local role of RXR in the penis-forming area during the development of imposex by TBT, thus suggesting a conserved function of RXR in penis formation at least within prosobranch gastropods.

Temporal trends (2004-2009) of imposex in rock shells Thais clavigera collected along the Korean coast associated with tributyltin regulation in 2003 and 2008

We investigated the temporal trend in contamination of butyltin compounds (BTs) along the Korean coast using imposex and tributyltin (TBT) burden in gastropods (Thais clavigera) as a biomonitor. Thais clavigera were collected from 26 locations with different shipping activities between 2004 and 2009 after restrictions on TBT-based antifouling paints were imposed in Korea. In the present study, imposex indices and TBT tissue concentrations significantly decreased over time from 2004 to 2009, confirming the effectiveness of TBT regulation. However, imposex in 2009 samples was still found. Significantly high imposex indices and TBT tissue residues were found in large ports containing commercial and ferry services compared with small ports and background areas. Imposex indices in background areas had decreased to zero, suggesting recovery from imposex caused by BT contamination. These results suggest that recovery from TBT contamination occurs faster in areas with very low maritime activities than areas with high maritime activities.