The environmental contaminant DDE fails to influence the outcome of sexual differentiation in the marine turtle Chelonia mydas

Systematic review of reptile reproductive toxicology to inform future research directions on endangered or threatened species, such as sea turtles

Threatened or endangered reptiles, such as sea turtles, are generally understudied within the field of wildlife toxicology, with even fewer studies on how contaminants affect threatened species reproduction. This paper aimed to better inform threatened species conservation by systematically and quantitatively reviewing available research on the reproductive toxicology of all reptiles, threatened and non-threatened. This review found 178 studies that matched our search criteria. These papers were categorized into location conducted, taxa studied, species studied, effects found, and chemicals investigated. The most studied taxa were turtles (n = 87 studies, 49%), alligators/crocodiles (n = 54, 30%), and lizards (n = 37, 21%). Maternal transfer, sex steroid alterations, sex reversal, altered sexual development, developmental abnormalities, and egg contamination were the most common effects found across all reptile taxa, providing guidance for avenues of research into threatened species. Maternal transfer of contaminants was found across all taxa, and taking into account the foraging behavior of sea turtles, could help elucidate differences in maternal transfer seen at nesting beaches. Sex steroid alterations were a common effect found with contaminant exposure, indicating the potential to use sex steroids as biomarkers along with traditional biomarkers such as vitellogenin. Sex reversal through chemical exposure was commonly found among species that exhibit temperature dependent sex determination, indicating the potential for both environmental pollution and climate change to disrupt population dynamics of many reptile species, including sea turtles. Few studies used in vitro, DNA, or molecular methodologies, indicating the need for more research using high-throughput, non-invasive, and cost-effective tools for threatened species research. The prevalence of developmental abnormalities and altered sexual development and function indicates the need to further study how anthropogenic pollutants affect reproductive output in threatened reptiles.

Organochlorines Contaminants in Eggs of Hawksbill (Eretmochelys imbricata) and Green Sea Turtles (Chelonia mydas) from Mexico coast

The investigation of organochlorine pesticides (OCPs) levels in sea turtles is an important issue in conservation research, due to the harmful effects of these chemicals. In the present study, OCPs concentrations were determined in the eggs of two sea turtle species (Eretmochelys imbricata and Chelonia mydas) collected from the Punta Xen and Isla Aguada (Mexican coast) in 2014 and 2015. Concentrations of 20 OCPs were analysed, including isomers of hexachlorocyclohexane, aldrin, chlordanes, endosulfans, methoxychlor, DDTs, and heptachlor. From the group of contaminants considered (analysed as families), the results revealed higher concentrations of ΣHCH and ΣDienes on both selected species. We analysed the relationship between turtle size and the OCPs concentrations; no correlation was found between the size of the female and concentrations in the eggs. In addition, principal component analysis indicated pattern differences between species and years, in good agreement with concentrations differences.

The current state and future directions of marine turtle toxicology research

Chemical contamination of marine turtles has been well documented in the literature, although information on the toxicological effects of these contaminants is poorly understood. This paper systematically and quantitatively presents the available marine turtle toxicological research (excluding oil chemicals and natural toxins) and the related fields of cell line establishment and biomarkers as indicators of exposure. Examination of the published literature identified a total of 49 papers on marine turtle toxicology, which were split into three categories: toxicity studies (n=33, 67%), cell line establishment (n=7, 14%), and publications using biomarkers (n=13, 27%). Toxicity studies were further broken down into four subcategories: those correlating contaminants with toxicological endpoints (n=16, 48%); in vitro exposure experiments (n=11, 33%); in vivo exposure experiments (n=5, 15%); and screening risk assessments using hazard quotients (n=3, 9%). In quantitatively assessing the literature, trends and gaps in this field of research were identified. This paper highlights the need for more marine turtle toxicology research on all species, particularly using high throughput and non-invasive in vitro assays developed for marine turtle cells, including investigations into further toxicological endpoints and mixture effects. This will provide more comprehensive species-specific assessment of the impacts of chemical contaminants on these threatened animals, and improve conservation and management strategies globally.

Establishment, characterization, and toxicological application of loggerhead sea turtle (Caretta caretta) primary skin fibroblast cell cultures

Pollution is a well-known threat to sea turtles but its impact is poorly understood. In vitro toxicity testing presents a promising avenue to assess and monitor the effects of environmental pollutants in these animals within the legal constraints of their endangered status. Reptilian cell cultures are rare and, in sea turtles, largely derived from animals affected by tumors. Here we describe the full characterization of primary skin fibroblast cell cultures derived from biopsies of multiple healthy loggerhead sea turtles (Caretta caretta), and the subsequent optimization of traditional in vitro toxicity assays to reptilian cells. Characterization included validating fibroblast cells by morphology and immunocytochemistry, and optimizing culture conditions by use of growth curve assays with a fractional factorial experimental design. Two cell viability assays, MTT and lactate dehydrogenase (LDH), and an assay measuring cytochrome P4501A (CYP1A) expression by quantitative PCR were optimized in the characterized cells. MTT and LDH assays confirmed cytotoxicity of perfluorooctanoic acid at 500 μM following 72 and 96 h exposures while CYP1A5 induction was detected after 72 h exposure to 0.1-10 μM benzo[a]pyrene. This research demonstrates the validity of in vitro toxicity testing in sea turtles and highlights the need to optimize mammalian assays to reptilian cells.

Experimental exposure of eggs to polybrominated diphenyl ethers BDE-47 and BDE-99 in red-eared sliders (Trachemys scripta elegans) and snapping turtles (Chelydra serpentina) and possible species-specific differences in debromination

Polybrominated diphenyl ethers (PBDEs) are a bioaccumulative, persistent, and toxic class of flame retardants that can potentially impact turtles in natural habitats via exposure through maternal transfer. To simulate maternal transfer in the present study, PBDE congeners BDE-47 and BDE-99 were topically applied to the eggshell and were allowed to diffuse into the egg contents of the red-eared slider (Trachemys scripta elegans) and snapping turtle (Chelydra serpentina). Eggs were topically dosed over 8 d to achieve a target concentration of 40 ng/g in the egg contents. Transfer efficiency was higher for BDE-47 than for BDE-99 in the red-eared sliders (25.8 ± 1.9% vs 9.9 ± 1.1%) and snapping turtles (31.3 ± 1.6% vs 12.5 ± 1.4%), resulting in greater BDE-47 and lower BDE-99 egg content concentrations relative to the 40 ng/g target. However, only 25.8 and 31.3% of the total BDE-47 and 9.9 and 12.5% of the total BDE-99 dose applied could be accounted for in the red-eared slider and snapping turtle egg contents, respectively. Additionally, increased BDE-47 in red-eared slider egg contents dosed with only BDE-99 indicate that BDE-99 might have been debrominated to BDE-47. The efficacy of topical dosing for administering desired embryonic exposures is clearly affected by the chemical properties of the applied compounds and was more successful for BDE-47 in both species.

Absorption of current use pesticides by snapping turtle (Chelydra serpentina) eggs in treated soil

Reptiles often breed within agricultural and urban environments that receive frequent pesticide use. Consequently, their eggs and thus developing embryos may be exposed to pesticides. Our objectives were to determine (i) if turtle eggs are capable of absorbing pesticides from treated soil, and (ii) if pesticide absorption rates can be predicted by their chemical and physical properties. Snapping turtle (Chelydra serpentina) eggs were incubated in soil that was treated with 10 pesticides (atrazine, simazine, metolachlor, azinphos-methyl, dimethoate, chlorpyrifos, carbaryl, endosulfan (I and II), captan, and chlorothalonil). There were two treatments, consisting of pesticides applied at application rate equivalents of 1.92 or 19.2 kg a.i/ha. Eggs were removed after one and eight days of exposure and analyzed for pesticides using gas chromatography coupled with a mass selective detector (GC-MSD) or high performance liquid chromatography (HPLC). Absorption of pesticides in eggs from soil increased with both magnitude and duration of exposure. Of the 10 pesticides, atrazine and metolachlor generally had the greatest absorption, while azinphos-methyl had the lowest. Chlorothalonil was below detection limits at both exposure rates. Our preliminary model suggests that pesticides having the highest absorption into eggs tended to have both low sorption to organic carbon or lipids, and high water solubility. For pesticides with high water solubility, high vapor pressure may also increase absorption. As our model is preliminary, confirmatory studies are needed to elucidate pesticide absorption in turtle eggs and the potential risk they may pose to embryonic development.

Chemical contamination of green turtle (Chelonia mydas) eggs in peninsular Malaysia: implications for conservation and public health

BACKGROUND

Persistent organic pollutants (POPs)-such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs)-and heavy metals have been reported in sea turtles at various stages of their life cycle. These chemicals can disrupt development and function of wildlife. Furthermore, in areas such as Peninsular Malaysia, where the human consumption of sea turtle eggs is prevalent, egg contamination may also have public health implications.

OBJECTIVE

In the present study we investigated conservation and human health risks associated with the chemical contamination of green turtle (Chelonia mydas) eggs in Peninsular Malaysia.

METHODS

Fifty-five C. mydas eggs were collected from markets in Peninsular Malaysia and analyzed for POPs and heavy metals. We conducted screening risk assessments (SRAs) and calculated the percent of acceptable daily intake (ADI) for POPs and metals to assess conservation and human health risks associated with egg contamination.

RESULTS

C. mydas eggs were available in 9 of the 33 markets visited. These eggs came from seven nesting areas from as far away as Borneo Malaysia. SRAs indicated a significant risk to embryonic development associated with the observed arsenic concentrations. Furthermore, the concentrations of coplanar PCBs represented 3 300 times the ADI values set by the World Health Organization.

CONCLUSIONS

The concentrations of POPs and heavy metals reported in C. mydas eggs from markets in Peninsular Malaysia pose considerable risks to sea turtle conservation and human health.

Organochlorine pesticide residues in sediment cores of sunderban wetland, northeastern part of Bay of Bengal, India, and their ecotoxicological significance

This paper presents the first comprehensive report of the organochlorine pesticide residues (OCs) such as hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane and its six metabolites (DDTs), and hexachlorobenzene (HCB) in core sediments (<63-microm particle size) from the Indian Sunderban wetland. The pooled mean values of the mass fraction of SigmaHCHs, HCB, and SigmaDDTs in the sediments were 0.05-12, 0.05-1.4, and 0.05-11.5 ng g(-1) dry weight, respectively. The vertical distribution of pesticides reveals an erratic pattern. The concentration of four isomers of HCHs reveals a heterogenic distribution where gamma-HCH (lindane) and beta-HCH shared the dominant part. The mass fraction of HCB did not show any sharp spatial variation. The prevailing sequence of DDT metabolites indicates an active degradation of the parent compound in the sediments and/or inputs of already degraded pp'DDT to the region. Peak concentrations of HCH isomers and DDT metabolites have the potential to induce ecotoxicological impact as per the sediment quality guidelines.

Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary, Vietnam

To assess the organochlorine contamination in the northeast coastal environment of Vietnam, a total of 41 surface sediments were collected from Ha Long Bay, Hai Phong Bay, and Ba Lat estuary, and analyzed for their organochlorine content. Organochlorine compounds (OCs) were widely distributed in the Vietnamese coastal environment. Among the OCs measured, DDT compounds predominated with concentrations ranging from 0.31 to 274 ng g(-1). The overall contamination level of DDTs in coastal sediments from northern Vietnam is comparable with those from other Asian countries. However, concentrations exceeding 100 ng g(-1) are comparable with high concentrations reported from India and China, the largest DDT consumers in the world. The overall concentrations of PCBs, HCHs, and chlordanes in surface sediments were in the ranges of 0.04-18.71 ng g(-1), not detected (n.d.) - 1.00 ng g(-1), and n.d. - 0.75 ng g(-1), respectively. Ha Long Bay and Hai Phong Bay were relatively more contaminated with DDTs and PCBs than other regions, respectively. In contrast, the distribution of HCHs was relatively homogeneous. OCs contamination in the coastal environment of Vietnam is closely related to shipping and industrial activities. The levels of DDT compounds in harbors and industrial areas exceeded their sediment quality guideline values suggested by Environment Canada [CCME (Canadian Council of Ministers of the Environment), 2002. Canadian sediment quality guidelines for the protection of aquatic life. In: Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment, Winnipeg, MB] and Australian and New Zealand [ANZECC and ARMCANZ, 2000. National water quality management strategy. Paper No. 4, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, vol. 1, The Guidelines. Australia. Document: http://www.deh.gov.au/water/quality/nwqms/volume1.html], indicating that adverse effects may occur to marine species in that areas.

Relationship of blood mercury levels to health parameters in the loggerhead sea turtle (Caretta caretta)

BACKGROUND

Mercury is a pervasive environmental pollutant whose toxic effects have not been studied in sea turtles in spite of their threatened status and evidence of immunosuppression in diseased populations.

OBJECTIVES

In the present study we investigate mercury toxicity in loggerhead sea turtles (Caretta caretta) by examining trends between blood mercury concentrations and various health parameters.

METHODS

Blood was collected from free-ranging turtles, and correlations between blood mercury concentrations and plasma chemistries, complete blood counts, lysozyme, and lymphocyte proliferation were examined. Lymphocytes were also harvested from free-ranging turtles and exposed in vitro to methylmercury to assess proliferative responses.

RESULTS

Blood mercury concentrations were positively correlated with hematocrit and creatine phosphokinase activity, and negatively correlated with lymphocyte cell counts and aspartate amino-transferase. Ex vivo negative correlations between blood mercury concentrations and B-cell proliferation were observed in 2001 and 2003 under optimal assay conditions. In vitro exposure of peripheral blood leukocytes to methylmercury resulted in suppression of proliferative responses for B cells (0.1 microg/g and 0.35 microg/g) and T cells (0.7 microg/g).

CONCLUSIONS

The positive correlation between blood mercury concentration and hematocrit reflects the higher affinity of mercury species for erythrocytes than plasma, and demonstrates the importance of measuring hematocrit when analyzing whole blood for mercury. In vitro immunosuppression occurred at methylmercury concentrations that correspond to approximately 5% of the individuals captured in the wild. This observation and the negative correlation found ex vivo between mercury and lymphocyte numbers and mercury and B-cell proliferative responses suggests that subtle negative impacts of mercury on sea turtle immune function are possible at concentrations observed in the wild.

Loggerhead sea turtle (Caretta caretta) egg yolk concentrations of persistent organic pollutants and lipid increase during the last stage of embryonic development

Data are scarce describing the concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides in sea turtle eggs. The purpose of this study was to establish appropriate sample collection methodology to monitor these contaminants in sea turtle eggs. Contaminant concentrations were measured in yolk samples from eggs that failed to hatch from three loggerhead sea turtle (Caretta caretta) nests collected in southern Florida to determine if concentrations change through embryonic development. One to three egg yolk samples per nest were analyzed from early, middle, and late developmental stages (n=22 eggs total). PCB and pesticide concentrations were determined by gas chromatography with electron capture detection (GC-ECD). Geometric mean concentrations of summation operatorPCBs (52 congeners), summation operatorDDTs, summation operatorchlordanes, and dieldrin in all eggs were 65.0 (range=7.11 to 3930 ng/g lipid), 67.1 (range=7.88 to 1340 ng/g lipid), 37.0 (range=4.04 to 685 ng/g lipid), and 11.1 ng/g lipid (range=1.69 to 44.0 ng/g lipid), respectively. Early and middle developmental stage samples had similar concentrations of PCBs and organochlorine pesticides on a wet-mass basis (ng/g tissue extracted), but the concentrations doubled by the late stage. This increase is most likely attributable to the 50% increase in lipid content observed in the late-stage yolk. These findings indicate that an early-stage sample cannot be directly compared to a late-stage sample, especially from different nests. These preliminary findings also allowed us to calculate the minimum number of eggs per nest required for analysis to obtain an acceptable mean concentration per nest. More research is required to investigate geographical trends of contaminant concentrations and potential health effects (i.e., abnormalities) caused by these contaminants on sea turtle development.

Effects of organochlorine contaminants on loggerhead sea turtle immunity: comparison of a correlative field study and in vitro exposure experiments

Several laboratory and field studies indicate that organochlorine contaminants (OCs), such as polychlorinated biphenyls (PCBs) and pesticides, modulate immune responses in rodents, wildlife, and humans. In the present study we examined the effects of OCs on immunity in free-ranging loggerhead sea turtles (Caretta caretta). Mitogen-induced lymphocyte proliferation responses, lysozyme activity, and OC concentrations were measured from blood samples. Mitogens chosen in the lymphocyte proliferation assay were phytohemagglutinin (PHA) and concanavalin A (ConA) for T-lymphocyte stimulation, and lipopolysaccharide (LPS) and phorbol 12,13-dibutyrate (PDB) for B-lymphocyte stimulation. Lysozyme activity was significantly and negatively correlated with whole-blood concentrations of 4,4 -dichlorodiphenyldichloroethylene (4,4 -DDE) and the sum of chlordanes. Lymphocyte proliferation responses stimulated by PHA, LPS, and PDB were significantly and positively correlated with concentrations of the sum of PCBs measured in whole blood. LPS- and PDB-induced proliferation were also significantly and positively correlated with 4,4 -DDE blood concentrations. These correlative observations in free-ranging turtles suggest that current, chronic exposure to OCs may suppress innate immunity and enhance certain lymphocyte functions of loggerhead sea turtles. To further test this hypothesis, lymphocyte proliferation was measured after in vitro exposure of peripheral blood leukocytes from 16 turtles to Aroclor 1254 (0-13.5 microg/mL) or 4,4 -DDE (0-13.4 microg/mL). Both contaminants increased PHA- and PDB-induced proliferation at concentrations below those that affected cell viability. Moreover, the concentrations that enhanced PDB-induced proliferation in vitro were similar to concentrations measured in turtles with the highest proliferative responses. The similarities between the in vitro experiments and the correlative field study suggest that OC exposure modulates immunity in loggerhead turtles.

p,p'-DDE fails to reduce the competitive reproductive fitness in Nigerian male guppies

The ecologically highly important effect of intermale competition is assessed here in a new approach to evaluating endocrine disruption at the population level. A guppy (Poecilia reticulata) male exposed to the antiandrogenic DDT metabolite p,p'-DDE competed against an unexposed male for the opportunity to fertilize a female. Offspring were then assigned to sires using microsatellites in genetic paternity analysis. In addition, a suite of male sexual characteristics including sperm count, coloration, and sexual behavior were also measured. p,p'-DDE produced no significant harmful effect on either the male sexual characteristics or the success in siring young, although the highest sublethal dose tested was only a factor 10 below the dose producing 100% mortality. At present, data on the antiandrogenic potency of p,p'-DDE are highly ambiguous. This study supports the increasing amount of evidence that the demasculinizing action of this chemical is often weak and highly variable across populations, even within the same species.

Developmental alterations as a result of in ovo exposure to the pesticide metabolite p,p'-DDE in Alligator mississippiensis

The pesticide metabolite p,p'-DDE (1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene), has been implicated in numerous reproductive and developmental abnormalities. Previous work has shown this ubiquitous contaminant to behave in an estrogenic or antiandrogenic manner, depending on the species and endpoints examined. In the current study, we examined the effects of embryonic exposure to p,p'-DDE in the alligator, a species that exhibits temperature-dependent sex determination. We compared sex ratios at an intermediate and all male producing temperature, as well as plasma testosterone (T) and gonad aromatase activity relative to untreated controls and in ovo estradiol-17beta (E(2))-treated neonates that served as positive estrogenic controls. We also compared oviductal epithelial cell height (ECH) and phallus size-estrogen and androgen responsive tissue, respectively. A female biased sex ratio was observed among hatchlings exposed to p,p'-DDE at 100 parts per billion (ppb) wet egg mass at the intermediate incubation temperature. No effect on sex determination was observed for p,p'-DDE at the all male producing temperature. Significant influence on sex determination was observed for E(2) at 100 and 0.1 ppb at the intermediate temperature and 100 ppb at the all male producing temperature. Both p,p'-DDE and E(2) failed to influence plasma T, gonadal aromatase activity, oviductal ECH, and phallus morphology at the concentrations used. Our data show that gonadal differentiation is highly sensitive to chemical perturbation relative to the other endpoints examined, and that the response to the interaction of dose and temperature should be taken into account in similar studies.

Effects of organochlorine compounds on cytochrome P450 aromatase activity in an immortal sea turtle cell line

Many classes of environmental contaminants affect the reproductive function of animals through interactions with the endocrine system. The primary components affected by endocrine active compounds (EACs) are the steroid receptors and the enzymes responsible for steroidogenesis. This study sought to develop an in vitro model for assessing EAC effects in sea turtles by examining their ability to alter cytochrome P450 aromatase (CYP19) activity. Aromatase is the enzyme responsible for the conversion of testosterone to estradiol. This enzyme is critical in the sexual differentiation of reptiles which demonstrate temperature-dependent sex determination. An immortal testis cell line GST-TS from a green sea turtle was grown in culture at 30 degrees C in RPMI 1640 media. The cells were exposed to three known aromatase inducers; dexamethasone (Dex), 8Br-cyclic AMP, or human chronic gonadotropin (HCG) and one aromatase inhibitor 4-androstenol-dione (4-OHA). In addition, the GST-TS cells were exposed to 0.1-30 microM atrazine and 3-100 microM 4,4'-DDE. The inducing compounds that have been shown to increase aromatase activity in other systems failed to induce aromatase activity in the GST-TS cells, yet exposure to the inhibiting compound, 4-OHA, did result in a significant reduction. Atrazine (0.1, 1.0 and 10 microM) significantly induced aromatase activity following a 24 h exposure, and 4,4'-DDE inhibited the activity but only at cytotoxic concentrations (100 microM). Based on these results, this in vitro model can be useful in examining the endocrine effects of EACs in sea turtles.

Developmental effects of embryonic exposure to toxaphene in the American alligator (Alligator mississippiensis)

A variety of organochlorine pesticides have been shown to adversely affect embryonic development. A number of abnormalities have been documented in alligators (Alligator mississippiensis) from highly-contaminated Lake Apopka, FL, USA that are similar to the results of experimental studies exposing embryos to pesticides. In the current study, we exposed developing alligator embryos to varying concentrations of toxaphene, a broad-spectrum pesticide found in relatively high concentration in Lake Apopka alligator egg yolk. The toxaphene, dissolved in 50 microl of ethanol, was applied topically to the eggshell just prior to the sex-determining period of development. Shortly after hatching, we examined a number of morphological and physiological endpoints to determine the consequences of sub-lethal embryonic exposure to toxaphene. Our results indicate that toxaphene had little or no effect on the morphological endpoints examined including body mass (BM) and size, liver, thyroid, and gonad development. In addition, toxaphene failed to affect sexual differentiation, or in vitro thyroxin, testosterone (T), and estradiol production. However, male plasma T concentration was higher in animals treated with 10 and 0.01 microg toxaphene/kg (based on mean egg mass) than control males. Because in vitro T production was not different among control groups, we suggest the difference in plasma T could be due to differences in hypothalamic-pituitary stimulation of the gonad or hepatic steroid degradation. This study indicates that technical grade toxaphene, at the applied doses, does not induce the same developmental abnormalities associated with alligators living in Lake Apopka. Future studies should consider the effects of embryonic exposure to a mixture of chemicals, including toxaphene metabolites, on development in alligators to better evaluate the consequences of environmental contamination.

Abnormal bone composition in female juvenile American alligators from a pesticide-polluted lake (Lake Apopka, Florida)

Reproductive disorders have been found in pesticide-exposed alligators living in Lake Apopka, Florida (USA). These disorders have been hypothesized to be caused by exposure to endocrine- disruptive estrogen-like contaminants. The aim of this study was to expand our analysis beyond previous studies by investigating whether bone tissue, known to be affected by sex steroid hormones, is a potential target of endocrine disruptors. Long bones from 16 juvenile female alligators from Lake Apopka (pesticide-contaminated lake) and Lake Woodruff (control lake) were evaluated by peripheral quantitative computed tomography. We observed significant differences in bone composition, with female alligators from the contaminated lake having greater trabecular bone mineral density (BMD), total BMD, and trabecular mineral content compared with females from the control lake (p < 0.05). Increased trabecular and total BMD measurements suggest that juvenile female alligators from Lake Apopka were exposed to contaminants that created an internal environment more estrogenic than that normally observed. This estrogenic environment could be caused by both natural and anthropogenic compounds. Effects on BMD indicate interference with bone homeostasis. We hypothesize that contaminants present in the lake inhibit the natural and continuous resorption of bone tissue, resulting in increased bone mass. Although this is the only study performed to date examining effects of environmental estrogenic compounds on alligator bones, it supports previous laboratory-based studies in rodents. Further, this study is important in demonstrating that the alterations in morphology and physiology induced in free-ranging individuals living in environments contaminated with endocrine-active compounds are not limited to a few systems or tissues; rather, effects can be observed in many tissues affected by these hormones.

Horizontal and vertical distribution of PCBs and chlorinated pesticides in sediments from Masan Bay, Korea

Horizontal and vertical distributions of organochlorine compounds (OCs) were determined in sediments from Masan Bay. The concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), HCB, hexachlorocyclohexanes (HCHs) and chlordane related compounds (CHLs) in sediments were in the range of 1.24-41.4, 0.28-89.2, 0.02-0.59, nd-1.03, and nd-2.56 ng/g, respectively. The spatial distribution of OCs showed a negative gradient from the inner of the bay to outer part of the bay, indicating that the source of OCs was probably located inside the bay. Compositional pattern of PCB congeners showed a relatively high concentration of high-chlorinated congeners in the inner part of the bay and a relatively low concentration of low-chlorinated congeners in the outer part. In sediment core from Masan Bay maximum concentrations of PCBs and DDTs are observed in the subsurface samples and correspond to an age of early 1980s and late 1960s. The concentration profiles of PCBs and DDTs in sediments of Masan Bay appear to correspond to use of PCBs and DDTs in Korea.

Experimental manipulation of steroid concentrations in circulation and in egg yolks of turtles

Steroid hormones in egg yolks are increasingly recognized as an important component of maternal and offspring fitness in oviparous vertebrates. Yet, except for in birds, the mechanism by which females allocate these resources is poorly understood. We manipulated systemic levels of hormones in reproductively mature female red-eared slider turtles (Trachemys scripta elegans) with silastic implants to test the hypothesis that hormones are allocated to developing follicles as a quantitative function of circulating levels in the females. Turtles exhibited similar amounts (<1 ng/ml) of circulating steroids (dihydrotestosterone, estradiol-17 beta, or testosterone) in early September immediately prior to experimental manipulation. After treatment with silastic implants, circulating levels of steroids increased markedly. By the following April after hibernation, circulating levels of dihydrotestosterone had returned to preimplantation levels, but circulating levels of estradiol-17 beta and testosterone in estradiol-17 beta- and testosterone-treated turtles, respectively, remained substantially elevated through April. Focusing on testosterone, we detected nearly six-fold higher concentrations in yolk from mature follicles from testosterone-treated turtles than in yolk from mature follicles from control turtles. Our results provide support for the hypothesis that concentrations of steroids in egg yolks of turtles reflect circulating concentrations of steroids during follicular development rather than the hypothesis that females selectively allocate specific amounts of steroid hormones to each egg separately. Our findings also highlight an unambiguous physiological mechanism by which nongenetic maternal effects in oviparous species can directly influence the nutritional milieu experienced by developing embryos.

Dichlorodiphenyltrichloroethane (DDT): ubiquity, persistence, and risks

Due to uncontrolled use for several decades, dichlorodiphenyltrichloroethane (DDT), probably the best known and most useful insecticide in the world, has damaged wildlife and might have negative effects on human health. This review gives a brief history of the use of DDT in various countries and presents the results of epidemiologic and experimental studies of carcinogenesis. Even though its use has been prohibited in most countries for ecologic considerations, mainly because of its negative impact on wildlife, it is still used in some developing countries for essential public health purposes, and it is still produced for export in at least three countries. Due to its stability and its capacity to accumulate in adipose tissue, it is found in human tissues, and there is now not a single living organism on the planet that does not contain DDT. The possible contribution of DDT to increasing the risks for cancers at various sites and its possible role as an endocrine disruptor deserve further investigation. Although there is convincing experimental evidence for the carcinogenicity of DDT and of its main metabolites DDE and DDD, epidemiologic studies have provided contrasting or inconclusive, although prevailingly negative, results. The presence and persistence of DDT and its metabolites worldwide are still problems of great relevance to public health. Efficient pesticides that do not have the negative properties of DDT, together with the development of alternative methods to fight malaria, should be sought with the goal of completely banning DDT.

Salmonid sexual development is not consistently altered by embryonic exposure to endocrine-active chemicals

Fish sexual development is sensitive to exogenous hormone manipulation, and salmonids have been used extensively as environmental sentinels and models for biomedical research. We simulated maternal transfer of contaminants by microinjecting rainbow trout (Oncorhynchus mykiss) and chinook salmon (Oncorhynchus tshawytscha) embryos. Fish were reared for 6 months and sexed, and gonads were removed for histology and measurement of in vitro steroid production. Analysis of fat samples showed that dichlorodiphenylethylene (DDE) levels, o, p'M-DDE and p,o, p'-DDE isomers, were elevated 6 months after treatment. A preliminary study showed an increased ratio of males to females after treatment with 80 mg/kg and 160 mg/kg of the xenoestrogen o,o, p'-DDE. One fish treated with 160 mg/kg o,o, p'-DDE had gonads with cells typical of both males and females. A follow-up study, using more fish and excluding the highly toxic 160 mg/kg o,o, p'-DDE dose, showed no effect on sex ratio or gonadal histology. Embryonic exposure of monosex male trout, monosex female trout, and mixed sex salmon to o, o, p'-DDE, p,o, p'-DDE, mixtures of DDE isomers, and octylphenol failed to alter sexual development. We observed no treatment-dependent changes in in vitro gonadal steroid production in any experiments. Trout exposed in ovo and reared to maturity spawned successfully. These results suggest that mortality attributable to the xenoestrogens o,o, p'-DDE, chlordecone, and octylphenol, and the antiandrogen p,o, p'-DDE, is likely to occur before the appearance of subtle changes in sexual development. Because trout appeared to be sensitive to endocrine disruption, we cannot dismiss the threat of heavily contaminated sites or complex mixtures to normal sexual development of salmonids or other aquatic organisms.

Sex reversal effects of environmentally relevant xenobiotic concentrations on the red-eared slider turtle, a species with temperature-dependent sex determination

Xenobiotics suspected of being estrogenic-the PCB aroclor 1242 and the pesticides toxaphene, dieldrin, p,p'-DDD, cis-Nonachlor, trans-Nonachlor, p,p'-DDE, and chlordane-were examined for their ability to override a male-producing incubation temperature and result in female hatchlings in the red-eared slider, a turtle with temperature-dependent sex determination. Compounds were assayed in the environmentally relevant concentrations detected in alligator eggs from Lake Apopka, Florida, singly, in concert with one another, and with estradiol. Compounds assayed alone and resulting in significant sex reversal were trans-Nonachlor, cis-Nonachlor, aroclor 1242, p,p'-DDE, and chlordane. When administered with estradiol, only one of the compounds, chlordane, caused sex reversal at significant levels. When applied together, however, the eight compounds assayed resulted in significant sex reversal.