Occurrence Of Intersex Research Articles

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.

Histological Evaluation of Gonad Impairments in Russian Sturgeon (Acipenser gueldenstaedtii) Reared in Recirculating Aquatic System (RAS).

Simple SummaryThe growing interest in sturgeon aquaculture necessitates the constant development of rearing techniques with special emphasis on the maintenance of high fish reproduction performance. However, there is a substantial lack of knowledge regarding gonadal impairments in sturgeons, even though the occurrence of such disorders poses a significant threat to the future of both commercial and conservation farming. Therefore, the aim of the research was to determine potential pathologies in the gonads of over-four-year old Russian sturgeon (Acipenser gueldenstaedtii) reared in the controlled conditions of recirculating aquatic systems (RAS). RAS have gained popularity in recent years, as they are considered the most environmentally friendly way of producing fish. Nevertheless, there are many issues that need to be resolved regarding sturgeon RAS farming, including its effect on gonadal development and, therefore, fish reproduction capacity. A detailed histological analysis revealed multiple gonadal disorders in the analyzed sturgeon, some of which can contribute to decreased fish fertility or even sterility. The female-biased sex ratio and the character of the identified impairments indicates that the observed germinal tissue disruptions might originate from estrogenic endocrine disturbances. Therefore, for the further sustainable development of sturgeon RAS aquaculture, there is an urgent need to identify and eliminate the causes of such disruptions.The aim of the study was to raise an issue concerning gonadal impairments in sturgeon reared in recirculating aquatic systems (RAS). In the present study, an in-depth histological evaluation in terms of gonadal pathologies was performed on over-4-year-old (1600 days post-hatching) Russian sturgeon (Acipenser gueldenstaedtii) reared under indoor RAS. A female-biased sex ratio, intersex occurrence, ovarian fat overgrowth, T-cell infiltration and follicle atresia were the most commonly observed disorders in the analyzed gonads. The combined processes of oocyte autophagy and follicular cell apoptosis were engaged in follicular atresia; however, atretic follicles showed a varied morphology, whereas oogonia and oocytes in the early stages of meiosis, as well as spermatogonia, underwent degeneration by apoptosis. The most severe pathology was observed in females with abundant intra-ovarian fat deposition. The extremely fatty ovaries were noted to lose the majority of ovarian follicles, which directly leads to fish sterility. The identified impairments might be related to estrogenic endocrine disruption, as feminization and unspecific vitellogenin synthesis were detected, although the sources of the observed pathologies can be diverse. Therefore, the presented research lays the groundwork for further studies on reproductive disorders in this prized and endangered fish species.

SAT-732 Historical Occurrence of Intersex in Largemouth Bass (Micropterus Salmoides) and Smallmouth Bass (Micropterus Dolomieu)

The widespread occurrence of gonadal intersex (presence of testicular oocytes) has been recently reported in populations of Largemouth Bass (Micropterus salmoides) and Smallmouth Bass Micropterus dolomieu) from populations across North America. To evaluate the historical occurrence of intersex in bass species, gonads were examined visually and histologically from Largemouth Bass and Smallmouth Bass from museum specimens collected from 16 States. These fishes were collected between 1823-1965, before the widespread discharge of estrogenic chemicals to surface waters via wastewater effluents. All females examined had normal ovaries. Intersex gonads were identified in 17.8 % of male Largemouth Bass, and in 14.2% of male Smallmouth Bass. The intensity of testicular oocytes in some males was as great as observed since 2000. These results indicate that the occurrence of this form of intersex in these bass species is not a recent phenomenon.

Gradual, temperature-induced change of secondary sexual characteristics in Trichogramma pretiosum infected with parthenogenesis-inducing Wolbachia.

Intersex is an intermediate stage of sexual differentiation in insects. Determining intersex morphology and the cause of its production will aid in the understanding of the mechanism of sexual differentiation in insects. In this paper, Wolbachia-infected Trichogramma pretiosum (T. preW+) that shows thelytokous parthenogenesis were used as subjects. In order to determine the causes of the T. preW+ intersex and the influence of parental generation temperature on gradual changes in secondary masculinization in intersex offspring, we examined the occurrence of intersex offspring (F1 and F2 generation) after the parental generations were treated with high temperature (27, 29, 31, and 33 °C) and described the external morphology of the intersexes. The results showed that the T. preW+ parental generation temperature is positively correlated with the probability of intersex offspring. The probability of F1 intersex is significantly higher than that of F2 intersex in different high temperature. The degree of secondary masculinization in T. preW+ intersexes increases as parental generation temperature increases. In addition, our study first identified 11 intersex types in T. preW+ and found that the primary and secondary sexual characteristics showed a regular distribution. We also found that the D type and H type of intersex have the highest frequency of appearance. The external genitalia of most intersexes were female, and only three intersex types have male external genitalia. Conclusions were ultimately obtained: Wolbachia is a direct factor that causes the occurrence of intersexes, while high temperature is an indirect factor that determines the external morphology of intersexes. The effects of high temperature on T. preW+ intersexes is passed through the parental generation to offspring, and this maternal effect weakens as the number of generations increases. In T. preW+ intersex individuals, most exhibit female primary sexual characteristics, and secondary sexual characteristics exhibit signs of masculinization.

Metformin-induced endocrine disruption and oxidative stress of Oryzias latipes on two-generational condition.

Metformin has been treated for diabetes (type 2). Nowadays, this compound is frequently found in ambient water, influent/effluent of a wastewater treatment plant. To evaluate the metformin aquatic toxicity under a multi-generational exposure regimen, we exposed Oryzias latipes to metformin for two generations (133 d) and investigated its adverse effects. In the F0 generation, metformin significantly elevated gene expression for cytochrome P450 19a (CYP19a) and estrogen receptor α (ERα) in male fish; in female fish, the treatment decreased gene expression of vitellogenin (VTG2) and ERβ1, suggesting endocrine disruption (one-way ANOVA, p < 0.05). Intersex occurrence of F0 female fish were found in a concentration-dependent manner, whereas no significant changes in fecundity and hatching rate were observed (p < 0.05). Metformin increased the reactive oxygen species (ROS) content, and decreased the glutathione (GSH) content in F0 male fish compared with those of the control (one-way ANOVA, p > 0.05). In F0 female fish, metformin increased catalase activity compared with that of the control (p > 0.05). The results demonstrated that metformin leads to oxidative stress and two-generation endocrine disruption in O. latipes. These results may be useful for better understanding metformin toxicity mechanism.

Relation of contaminants to fish intersex in riverine sport fishes

Endocrine active compounds (EACs) are pollutants that have been recognized as an emerging and widespread threat to aquatic ecosystems globally. Intersex, the presence of female germ cells within a predominantly male gonad, is considered a biomarker of endocrine disruption caused by EACs. We measured a suite of EACs and assessed their associated impacts on fish intersex occurrence and severity in a large, regulated river system in North Carolina and South Carolina, USA. Our specific objective was to determine the relationship of contaminants in water, sediment, and fish tissue with the occurrence and severity of the intersex condition in wild, adult black bass (Micropterus), sunfish (Lepomis), and catfish (Ictaluridae) species at 11 sites located on the Yadkin-Pee Dee River. Polycyclic aromatic hydrocarbons (PAHs), ethinylestradiol (EE2), and heavy metals were the most prevalent contaminants that exceeded effect levels for the protection of aquatic organisms. Fish intersex condition was most frequently observed and most severe in black basses and was less frequently detected and less severe in sunfishes and catfishes. The occurrence of the intersex condition in fish showed site-related effects, rather than increasing longitudinal trends from upstream to downstream. Mean black bass and catfish tissue contaminant concentrations were higher than that of sunfish, likely because of the latter's lower trophic position in the food web. Principal component analysis identified waterborne PAHs as the most correlated environmental contaminant with intersex occurrence and severity in black bass and sunfish. As indicated by the intersex condition, EACs have adverse but often variable effects on the health of wild sport fishes in this river, likely due to fluctuations in EAC inputs and the dynamic nature of the riverine system. These findings enhance the understanding of the relationship between contaminants and fish health and provide information to guide ecologically comprehensive conservation and management decisions.

Sex Determination Model in Pink Salmon Oncorhynchus gorbuscha (Walbaum, 1792) (Salmonidae, Osteichthyes) Controlled by Multi-Copy Genes Located in Sex Chromosomes.

This article is devoted to presenting the hypothesis explaining the fact of a considerable prevalence of phenotypic males among the triploid pink salmon as well as the regular occurrence of intersexes, which were revealed by us. This hypothesis also explains the large proportion (in some cases) in pink salmon populations of the individuals whose genetic sex does not match the phenotypic sex. We assume that the genes encoding the factors that contribute to the transformation of individuals into males (but not the marker sequences of the Y chromosome) are present not only in the Y chromosome of pink salmon but also in the X chromosome, although in smaller quantities.

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.

Mechanistic study of chlordecone-induced endocrine disruption: Based on an adverse outcome pathway network

The adverse outcome pathway (AOP) framework could be helpful for chemical risk assessment and mechanistic research. The aim of the present study was to unravel the mechanism of chlordecone-induced endocrine disruption by illustrating the main molecular initiating event (MIE)/perturbations responsible for the observed effects. In silico simulations were performed to predict the MIE(s), and the results pointed to agonistic interaction with estrogen receptors (ERα, ERβ), androgen receptor (AR), cytochrome P450 (CYP19A) by chlordecone. In vivo endocrine disruptions were evaluated in rare minnow (Gobiocypris rarus) exposed to 0.01, 0.1, 1 and 10 μg L−1 chlordecone from 2 h post-fertilization until sexually mature. In the females, increases of vitellogenin (vtg) mRNA levels in liver and gonad, plasma estradiol (E2), testosterone (T) and E2/T, and renalsomatic index confirmed the role of agonism of ER and CYP19A as MIEs, but the decreased gonadosomatic index, degenerated ovaries as well as the feed-forward response pointed to other potential but important MIEs and corresponding AOPs. In the males, increased E2/T ratio, increased testis vtg mRNA levels and occurrence of intersex confirmed the roles of agonism of ERα and CYP19A as main MIEs in chlordecone-induced endocrine disruptions. Our results also fetches out the limit of AOPs in predicting the adverse outcomes and explaining the mechanism of chemicals at present, thus reflected a critical need for expanding AOPs and AOP network before using it in chemical risk assessment.

Survey of Intersex Occurrence in Largemouth Bass (Micropterus salmoides) from the Upper Illinois River Waterway

Abstract Intersex condition (ooctyes in testicular tissue) has been documented in many watersheds among a diverse variety of fishes worldwide. However, few studies have tested for the occurrence of the condition in fishes from rivers of the American Midwest. Midwestern watersheds, such as the Illinois River Waterway, U.S.A. may provide important new information about the effects of endocrine disrupting chemicals (EDCs) on fishes because of the variety of urban, industrial, and agricultural land uses within the watersheds. A first step in the study of EDCs in any ecosystem is a survey to document the symptoms of EDC exposure, such as intersex condition. Our objective was to test for intersex condition in male largemouth bass Micropterus salmoides in the lower Des Plaines River, an area directly affected by surface runoff and wastewater effluents from the Chicago Metropolitan Area. Histological analysis indicated that testicular oocytes were present in 21 of 51 (41%) largemouth bass sampled and oocyte numbe...

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.

Steroidogenesis and phase II conjugation during the gametogenesis of thicklip grey mullet (Chelon labrosus) from a population showing intersex condition

Steroidogenesis, the process by which steroid hormones are synthesized, involves a vast number of enzymes and biochemical pathways that are susceptible to chemical modulation. Endocrine disrupting compounds (EDCs) are of special concern since they can alter hormone homeostasis by interfering with synthesis, transport and elimination of hormones. It is important to understand gender differences and the natural variation in steroid balance through gamete development in fish exposed to EDCs. The aim of this study was to determine mRNA levels of genes encoding for Steroidogenic Acute Regulatory (star) protein; the steroidogenic enzymes P450 11β hydroxylase (cyp11b1) and P450 aromatase (cyp19a1a); as well as the phase II conjugation enzymes sulfotransferase (sult) and UDP-glucuronosyltransferase (ugt), together with the activity of P450 aromatase and plasma levels of 17β-estradiol (E2) and 11-ketotestosterone (11-KT), at different gametogenic stages and in intersex individuals of the thicklip grey mullet Chelon labrosus. Results demonstrated that the transcription levels of star, sult and ugt and levels of E2 and 11-KT in plasma significantly changed with the interaction between gender and reproductive stage. Cyp11b1 and cyp19a1a transcription levels were significantly different between genders while the activity of P450 aromatase varied significantly between genders and reproductive stages. Results from a multivariate assessment demonstrated that measured endpoints distinguished male, female and intersex mullets at immature gametogenic stage. Intersex distinction was based on sult, ugt and cyp19a1a transcript levels and P450 aromatase activity. The present work provides data to be used in future experimental designs with C. labrosus species, and gives new clues about the molecular events that lead to intersex occurrence in mullets.

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.

Survey of Intersex Largemouth Bass from Impoundments in Georgia USA

AbstractIntersex fish are increasingly being reported worldwide, primarily in rivers that receive treated wastewater, but few studies have investigated intersex in waters that do not receive wastewater. In a recent reconnaissance survey of intersex fish in North America, a high rate of intersex was reported for Largemouth Bass Micropterus salmoides in some southeastern U.S. rivers; however, the occurrence of intersex in impoundments has not been well described, especially on a statewide scale. Therefore, our objective for this project was to survey the occurrence of intersex Largemouth Bass in a variety of impoundment habitats across Georgia. Largemouth Bass were collected from 11 impoundments without direct municipal or agricultural wastewater inputs. Gonads from all male Largemouth Bass were evaluated for the incidence and severity of the intersex condition based on presence and arrangement of testicular oocytes. Overall 48% of male Largemouth Bass collected from impoundments were intersex, which was found in 9 of the 11 impoundments. Among impoundments, incidence of intersex ranged from 0 to 82% of the males sampled and surface area of the impoundment was a significant predictor of intersex incidence. Intersex fish were smaller than normal males, but population‐level effects of intersex and causative factors of endocrine disruption in the impoundments remain unknown. The high incidence of intersex males in small impoundments demonstrates that the condition is not confined to rivers and suggests that factors other than those previously associated with intersex (i.e., municipal wastewater) may be involved.

Biosensor Medaka for Monitoring Intersex Caused by Estrogenic Chemicals

Estrogenic chemicals can induce intersex in fish species leading to disturbance of spermatogenesis and impairment of reproductive success. To overcome the shortcomings of conventional histopathological observation on intersex (low sensitivity, relatively poor accuracy, long experimental periods, as well as laborious and time-consuming), we generated a pMOSP1-EGFP transgenic medaka fish model. In this transgenic fish, the green fluorescence protein (GFP) reporter gene was derived by the regulatory elements of the OSP1 gene, which is a specific and sensitive molecular biomarker for indicating intersex occurrence in male medaka fish exposed to estrogenic chemicals. The transgenic GFP was faithfully expressed in ovaries and in testes with intersex, perfectly mimicking the expression pattern of endogenous OSP1. In intersex testis, the diameters of primary oocytes which could be distinguished by GFP fluorescence observation were as small as 10 μm, lower than that (more than 20 μm) which is observable by histopathology. Using the novel transgenic medaka fish, intersex was observed after 90-day exposure to 0.75 ng/L 17α-ethinyloestradiol (EE2) (0-90 dph), but only at concentrations of at least 1.38 ng/L EE2 by histopathology. An effectiveness of a short-term in vivo assay for screening estrogenic chemicals that can monitor intersex appearance at early sex developmental stage (about 30 dph) in male medaka fish was also demonstrated by assessing the intersex induction of EE2, 17β-estradiol and 4-nonylphenol. This newly developed assay provides an enhanced ability for screening and testing estrogenic chemicals with the potential to induce intersex and studying their biological impacts.

First report of intersex in the signal crayfish Pacifastacus leniusculus (Dana, 1852)

The reproductive strategies of species of non-indigenous crayfish make an important issue in astacological research. Although crayfish reproduction has been well studied, there is little information available on the occurrence of intersexuality. We report the first evidence of intersex in the signal crayfish, Pacifastacus leniusculus (Dana, 1852). An intersexual specimen was found among five tested signal crayfish. Morphology revealed both male and female genital openings, as well as male gonopods. The specimen superficially appeared male but contained both testes and ovaries, with an atypical dispersed structure. Sperm was obtained from this crayfish. Histology showed both spermatocytes and oocytes. The gonadosomatic index (GSI = 3.79) was considered as a morphometric parameter of the intersexual crayfish. The ova present in the intersex male raised its GSI to the three-fold of that of normal males.

Assessing the Continuous Impact of Tributyltin from Antifouling Paints in a Brazilian Mangrove Area Using Intersex in Littoraria angulifera (Lamarck, 1822) as Biomarker

Intersex is a sensitive biomarker of TBT exposure and effects in littorinid gastropods and described for the mangrove periwinkle Littoraria angulifera for the first time in this study. The objective was to describe the occurrence of intersex in L. angulifera, to propose the species as a sentinel organism to assess TBT contamination, and to characterize the contamination in mangroves. The study was carried out in 2009 by sampling at 20 stations near harbors and marinas and at a reference station on the coast of Espírito Santo Estate, Brazil. At the reference station, no intersex specimens were found, while at 20 sampling stations 51% of the females exhibited different degrees of intersex development, including the occurrence of functionally sterilized females. The highest incidence of intersex and greatest intersex intensities was found in areas close to marinas and shipyards indicating that vessel-related activities are still the main source of TBT contamination. L. angulifera collected from stations in areas with well-preserved mangroves was larger than specimens collected from other areas. These differences are attributed to environmental quality and not to occurrence of intersex. The results indicate that this region is still affected by TBT contamination and that L. angulifera has the required sensitivity to be used as a bioindicator.

Prevalence and patterns of infection by the epicaridean parasite,Gyge ovalisand the emergence of intersex in the estuarine mud shrimp,Upogebia major

A population of the mud shrimp,Upogebia major, inhabiting Kasaoka Inlet had a higher frequency of intersex males compared to other populations in the Seto Inland Sea, Japan. This population also featured a high prevalence of the branchial epicaridean parasite,Gyge ovalis, and inhabited a tidal flat characterized by increasingly softer sediments going into the lower tidal areas. We examined the rates at which infection co-occurred with intersex features and checked whether infection patterns varied with intersex occurrence according to host size and tidal level position. Fewer specimens were both intersex and infected than those having only one of either condition; infection was not a significant predictor of intersex. However, infection in young hosts that recovered from the parasite could be associated with the intersex morphologies and account for the majority of cases that were intersex but parasite-free. Deletions of the cuticular ridge (CRD) between the first and second abdominal segment and tidal level position were correlated with intersex. Lower tidal zone mud shrimp were, respectively, three and four times more likely to be intersex and exhibit CRD than those in the upper tidal zone. Potentially inclusive factors that may influence these trends are higher rates of early infection and increased exposure to sediment-bound pollutants in mud shrimp inhabiting the lower tidal areas.

Occurrence and degree of intersex (testis–ova) in darters (Etheostoma SPP.) across an urban gradient in the Grand River, Ontario, Canada

The variability and extent of the intersex condition (oocytes in testes, or testis-ova) was documented in fish along an urban gradient in the Grand River, Ontario, Canada, that included major wastewater treatment plant outfalls. A method for rapid enumeration of testis-ova was developed and applied that increased the capacity to quantify intersex prevalence and severity. Male rainbow darters (Etheostoma caeruleum) sampled downstream of the first major wastewater outfall (Waterloo) had a significant increase, relative to 4 upstream reference sites, in the mean proportion of fish with at least 1 testis-oocyte per lobe of testes (9-20% proportion with ≤ 1 testis-oocyte/lobe vs 32-53% and >1.4 testis-oocyte/lobe). A much higher mean incidence of intersex proportion and degree was observed immediately downstream of the second wastewater outfall (Kitchener; 73-100% and 8-70 testis-oocyte/lobe); but only 6.3 km downstream of the Kitchener outfall, the occurrence of intersex dropped to those of the reference sites. In contrast, downstream of a tertiary treated wastewater outfall on a small tributary, intersex was similar to reference sites. Estrogenicity, measured using a yeast estrogen screen, followed a similar pattern, increasing from 0.81 ± 0.02 ng/L 17b-estradiol equivalents (EEq) (Guelph), to 4.32 ± 0.07 ng/L (Waterloo), and 16.99 ± 0.40 ng/L (Kitchener). Female rainbow darter downstream of the Kitchener outfall showed significant decreases in gonadosomatic index and liver somatic index, and increases in condition factor (k) relative to corresponding reference sites. The prevalence of intersex and alterations in somatic indices suggest that exposure to municipal wastewater effluent discharges can impact endocrine function, energy use, and energy storage in wild fish.