RESUMEN
Species displaying temperature-dependent sex determination (TSD) are especially vulnerable to the effects of a rapidly changing global climate due to their profound sensitivity to thermal cues during development. Predicting the consequences of climate change for these species, including skewed offspring sex ratios, depends on understanding how climatic factors interface with features of maternal nesting behaviour to shape the developmental environment. Here, we measure thermal profiles in 86 nests at two geographically distinct sites in the northern and southern regions of the American alligator's (Alligator mississippiensis) geographical range, and examine the influence of both climatic factors and maternally driven nest characteristics on nest temperature variation. Changes in daily maximum air temperatures drive annual trends in nest temperatures, while variation in individual nest temperatures is also related to local habitat factors and microclimate characteristics. Without any compensatory nesting behaviours, nest temperatures are projected to increase by 1.6-3.7°C by the year 2100, and these changes are predicted to have dramatic consequences for offspring sex ratios. Exact sex ratio outcomes vary widely depending on site and emission scenario as a function of the unique temperature-by-sex reaction norm exhibited by all crocodilians. By revealing the ecological drivers of nest temperature variation in the American alligator, this study provides important insights into the potential consequences of climate change for crocodilian species, many of which are already threatened by extinction.
Asunto(s)
Caimanes y Cocodrilos , Razón de Masculinidad , Temperatura , Animales , Cambio Climático , Ecosistema , Femenino , Masculino , Procesos de Determinación del SexoRESUMEN
Mercury is a widespread, naturally occurring contaminant that biomagnifies in wetlands due to the methylation of this element by sulfate-reducing bacteria. Species that feed at the top trophic level within wetlands are predicted to have higher mercury loads compared to species feeding at lower trophic levels and are therefore often used for mercury biomonitoring. However, mechanisms for mercury bioaccumulation in sentinel species are often poorly understood, due to a lack of long-term studies or an inability to differentiate between confounding variables. We examined mercury bioaccumulation patterns in the whole blood of American alligators (Alligator mississippiensis) from a long-term mark-recapture study (1979-2017) in South Carolina, USA. Using a growth model and auxiliary information on predicted age at first capture, we differentiated between age- and size-related variation in mercury bioaccumulation, which are often confounded in alligators due to their determinate growth pattern. Contrary to predictions that the oldest or largest individuals were likely to have the highest mercury concentrations, our best-supported model indicated a peak in mercury concentration at 30-40 years of age, depending on the sex, and lower concentrations in the youngest and oldest animals. To evaluate the robustness of our findings, we re-analyzed data from a previously published study of mercury in alligators sampled at Merritt Island National Wildlife Refuge in Florida. Unlike the South Carolina data, the data from Florida contained minimal auxiliary information regarding age, yet the best supported model similarly indicated a peaked rather than increasing relationship between mercury and body size, a less-precise indicator of age. These findings highlight how long-term monitoring can differentiate between confounding variables (e.g., age and size) to better elucidate complex relationships between contaminant exposure and demographic factors in sentinel species.
Asunto(s)
Caimanes y Cocodrilos , Envejecimiento , Animales , Bioacumulación , Monitoreo del Ambiente , Florida , Humanos , Islas , Mercurio , Dinámicas no Lineales , South CarolinaRESUMEN
To monitor physiological and toxicological conditions in an endangered species, noninvasive to minimally invasive sampling methods are needed. We analyzed peripheral blood cells to determine if we could monitor some physiological responses of the American alligator following capture stress. Juvenile American alligators were restrained for 16 h to examine the stress response in plasma and blood cells. Plasma corticosterone concentrations were increased by restraint as were plasma concentrations of aspartate aminotransferase (AST), creatine kinase (CK), uric acid, and glucose; a sexually dimorphic response was seen in AST and CK concentrations. The lapse time of restraint was associated with altered messenger RNA (mRNA) levels of the glucocorticoid receptor (GCR) in red blood cells and JUN proto-oncogene in both white and red blood cells. A two-way cluster analysis revealed that two major clusters of factors were associated with the responses seen: (a) mRNA levels of GCR and heat-shock proteins in both blood cells were associated with plasma corticosterone concentration, whereas (b) androgen receptors and JUN mRNA levels in both blood cells were associated with cloacal temperature and body composition. Blood cells appear to be an excellent source to examine the cellular stress response to steroid hormone signals in mRNA levels. We propose that this approach, using blood cells, could provide essential insights into the molecular responses associated with stress in reptiles as well as many other nontraditional model species, including endangered species.
Asunto(s)
Caimanes y Cocodrilos/sangre , ARN Mensajero/sangre , Estrés Fisiológico , Caimanes y Cocodrilos/fisiología , Animales , Aspartato Aminotransferasas/sangre , Temperatura Corporal , Corticosterona/sangre , Creatina Quinasa/sangre , Femenino , Genes jun , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Masculino , ARN Mensajero/metabolismo , Receptores Androgénicos/genética , Receptores Androgénicos/metabolismo , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Restricción FísicaRESUMEN
American alligators are exposed to mercury (Hg) throughout their natural range and may maternally transfer Hg into their eggs. Wildlife species are highly sensitive to Hg toxicity during embryonic development and neonatal life, and information on Hg transfer into eggs is critical when attempting to understand the effects of Hg exposure on developing oviparous organisms. To examine Hg transfer in alligators, the objectives of the present study were to 1) determine Hg concentrations in yolk (embryonic and neonatal food source) from wild alligator eggs collected from three locations - Yawkey Wildlife Center SC (YWC), Lake Apopka FL (LA), and Lake Woodruff FL (LW); 2) examine the relationship between THg concentrations in wild alligator nest material and egg yolk at Merritt Island National Wildlife Refuge, FL; 3) examine the Hg concentrations in wild maternal female alligators (blood) and the THg in corresponding egg yolks and embryos across three nesting seasons at a single location (YWC), and evaluate the relationship between nesting female THg concentrations (blood) and their estimated age and number of nesting years (YWC); and 4) assess the transfer of biologically-relevant Hg concentrations (based on Hg measured in maternal female blood) into embryos using an egg-dosing experiment. Mean total Hg (THg) concentrations observed at each site were 26.3 ng/g ± 11.0 ng/g (YWC), 8.8 ng/g ± 5.1 ng/g (LA), and 22.6 ng/g ± 6.3 ng/g (LW). No relationship was observed between THg in alligator nest material and corresponding yolk samples, nor between THg in maternal alligator blood and estimated age and number of nesting years of these animals. However, significant positive relationships were observed between THg in blood of nesting female alligators and THg in their corresponding egg yolk. We observed that 12.8% of the maternal blood THg is found in the corresponding egg yolk, and a highly significant correlation was observed between the two sample types (r = 0.66; p < 0.0001). The egg dosing experiment revealed that Hg did not transfer through the eggshell at developmental stage 19. Overall, this study provides new information regarding Hg transfer in American alligators which can improve biomonitoring efforts and may inform ecotoxicological investigations and population management programs in areas of high Hg contamination.
Asunto(s)
Caimanes y Cocodrilos/sangre , Monitoreo del Ambiente/métodos , Exposición Materna/efectos adversos , Mercurio/análisis , Óvulo/metabolismo , Contaminantes Químicos del Agua/análisis , Animales , Femenino , Florida , Lagos/química , Masculino , Mercurio/sangre , South Carolina , Contaminantes Químicos del Agua/sangreRESUMEN
Toxic trace element exposure occurs through release of the ubiquitous and naturally occurring elements arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg). The unique environmental conditions of the wetland ecosystems along the southeastern Atlantic coast of the United States lead to the accumulation of Hg which is greater than in most other ecosystems in the country. There are also point sources of As, Cd, and Pb in this region. To effectively monitor trace element concentrations, and consequently the potential human exposure, accessible local sentinel species are needed. In this study, concentrations of As, Cd, Pb, Hg and six other trace elements (Al, Ni, Cu, Zn, Se, Mo) were examined in American alligators (Alligator mississippiensis) from seven wetland sites in South Carolina and Florida and assessed for their utility as a sentinel species for human trace element exposure. Alligators were chosen as a potential sentinel as they share a common exposure with the local human population through their aquatic diet, and they are directly consumed commercially and through recreation hunting in this region. Sex was significantly related to the concentration of Zn, Mo, and Al, but not As, Pb, Hg, Cd, Se, or Cu. Site specific differences in element concentrations were observed for As, Pb, Hg, Cd, Se, Zn, and Mo. Size/age was significantly related to the element Hg and Pb concentrations observed. The observed concentration ranges for the four toxic elements, As (6-156â¯ng/g), Cd (0.3-1.3â¯ng/g), Pb (3-4872â¯ng/g), and Hg (39-2765â¯ng/g), were comparable to those previously reported in diverse human populations. In this region alligators are hunted recreationally and consumed by the local community, making them a vehicle of direct human toxic element exposure. We propose that the similarity in As, Cd, Pb, and Hg concentrations between alligators observed in this study and humans underscores how alligators can serve as a useful sentinel species for toxic element exposure.
Asunto(s)
Caimanes y Cocodrilos/metabolismo , Exposición a Riesgos Ambientales/análisis , Especies Centinela/metabolismo , Oligoelementos/metabolismo , Contaminantes Químicos del Agua/metabolismo , Animales , Florida , Humanos , South Carolina , HumedalesRESUMEN
The thyroid gland is sensitive to steroid hormone signaling, and many thyroid disrupting contaminants also disrupt steroid hormone homeostasis, presenting the possibility that thyroid disruption may occur through altered steroid hormone signaling. To examine this possibility, we studied short-term and persistent impacts of embryonic sex steroid exposure on thyroid physiology in the American alligator. Alligators from a lake contaminated with endocrine disrupting contaminants (Lake Apopka, FL, USA) have been shown to display characteristics of thyroid and steroid hormone disruption. Previous studies suggest these alterations arise during development and raise the possibility that exposure to maternally deposited contaminants might underlie persistent organizational changes in both thyroidal and reproductive function. Thus, this population provides a system to investigate contaminant-mediated organizational thyroid disruption in an environmentally-relevant context. We assess the developmental expression of genetic pathways involved in thyroid hormone biosynthesis and find that expression of these genes increases prior to hatching. Further, we show that nuclear steroid hormone receptors are also expressed during this period, indicating the developing thyroid is potentially responsive to steroid hormone signaling. We then explore functional roles of steroid signaling during development on subsequent thyroid function in juvenile alligators. We exposed alligator eggs collected from both Lake Apopka and a reference site to 17ß-estradiol and a non-aromatizable androgen during embryonic development, and investigated effects of exposure on hatchling morphometrics and thyroidal gene expression profiles at 5â¯months of age. Steroid hormone treatment did not impact the timing of hatching or hatchling size. Furthermore, treatment with steroid hormones did not result in detectable impacts on thyroid transcriptional programs, suggesting that precocious or excess estrogen and androgen exposure does not influence immediate or long-term thyroidal physiology.
Asunto(s)
Caimanes y Cocodrilos/genética , Caimanes y Cocodrilos/fisiología , Regulación del Desarrollo de la Expresión Génica , Esteroides/efectos adversos , Glándula Tiroides/fisiología , Caimanes y Cocodrilos/embriología , Animales , Vías Biosintéticas/genética , Femenino , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Hormonas Esteroides Gonadales/genética , Hormonas Esteroides Gonadales/metabolismo , Modelos Lineales , Masculino , Receptores Citoplasmáticos y Nucleares/genética , Receptores Citoplasmáticos y Nucleares/metabolismo , Glándula Tiroides/embriología , Hormonas Tiroideas/biosíntesisRESUMEN
Estrogens regulate key aspects of sexual determination and differentiation, and exposure to exogenous estrogens can alter ovarian development. Alligators inhabiting Lake Apopka, FL, are historically exposed to estrogenic endocrine disrupting contaminants and are characterized by a suite of reproductive abnormalities, including altered ovarian gene expression and abated transcriptional responses to follicle stimulating hormone. Here, we test the hypothesis that disrupting estrogen signaling during gonadal differentiation results in persistent alterations to ovarian gene expression that mirror alterations observed in alligators from Lake Apopka. Alligator embryos collected from a reference site lacking environmental contamination were exposed to estradiol-17 beta or a nonaromatizable androgen in ovo and raised to the juvenile stage. Changes in basal and gonadotropin-challenged ovarian gene expression were then compared to Apopka juveniles raised under identical conditions. Assessing basal transcription in untreated reference and Apopka animals revealed a consistent pattern of differential expression of key ovarian genes. For each gene where basal expression differed across sites, in ovo estradiol treatment in reference individuals recapitulated patterns observed in Apopka alligators. Among those genes affected by site and estradiol treatment were three aryl hydrocarbon receptor (AHR) isoforms, suggesting that developmental estrogen signaling might program sensitivity to AHR ligands later in life. Treatment with gonadotropins stimulated strong ovarian transcriptional responses; however, the magnitude of responses was not strongly affected by steroid hormone treatment. Collectively, these findings demonstrate that precocious estrogen signaling in the developing ovary likely underlies altered transcriptional profiles observed in a natural population exposed to endocrine disrupting contaminants.
Asunto(s)
Caimanes y Cocodrilos , Embrión no Mamífero/efectos de los fármacos , Disruptores Endocrinos/toxicidad , Estrógenos/toxicidad , Exposición Materna/efectos adversos , Ovario/efectos de los fármacos , Caimanes y Cocodrilos/embriología , Caimanes y Cocodrilos/genética , Animales , Reprogramación Celular/efectos de los fármacos , Reprogramación Celular/genética , Embrión no Mamífero/metabolismo , Desarrollo Embrionario/efectos de los fármacos , Desarrollo Embrionario/genética , Exposición a Riesgos Ambientales/efectos adversos , Femenino , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Lagos , Modelos Animales , Ovario/metabolismo , Oviparidad/efectos de los fármacos , Oviparidad/genética , Transcriptoma/efectos de los fármacos , Transcriptoma/genética , Contaminantes Químicos del Agua/toxicidadRESUMEN
Type 1 diabetes (T1D) is a chronic autoimmune disease that affects 1 in 300 children by age 18. T1D is caused by inflammation-induced loss of insulin-producing pancreatic beta cells, leading to high blood glucose and a host of downstream complications. Although multiple genes are associated with T1D risk, only 5% of genetically susceptible individuals actually develop clinical disease. Moreover, a growing number of T1D cases occur in geographic clusters and among children with low risk genotypes. These observations suggest that environmental factors contribute to T1D etiology. One potential factor, supported primarily by epidemiological studies, is the presence of nitrate and nitrite in drinking water. To test this hypothesis, female hatchling alligators were exposed to environmentally relevant concentrations of nitrate in their tank water (reference, 10mg/L, or 100mg/L NO3-N) from hatch through 5 weeks or 5 months of age. At each time point, endpoints related to T1D were investigated: plasma levels of glucose, triglycerides, testosterone, estradiol, and thyroxine; pancreas, fat body, and thyroid weights; weight gain or loss; presence of immune cells in the pancreas; and pancreatic beta cell number, assessed by antibody staining of nkx6.1 protein. Internal dosing of nitrate was confirmed by measuring plasma and urine nitrate levels and whole blood methemoglobin. Cluster analysis indicated that high nitrate exposure (most animals exposed to 100mg/L NO3-N and one alligator exposed to 10mg/L NO3-N) induced a profile of endpoints consistent with early T1D that could be detected after 5 weeks and was more strongly present after 5 months. Our study supports epidemiological data correlating elevated nitrate with T1D onset in humans, and highlights nitrate as a possible environmental contributor to the etiology of T1D, possibly through its role as a nitric oxide precursor.
Asunto(s)
Caimanes y Cocodrilos/sangre , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Tipo 1/inducido químicamente , Disruptores Endocrinos/toxicidad , Nitratos/toxicidad , Contaminantes Químicos del Agua/toxicidad , Caimanes y Cocodrilos/crecimiento & desarrollo , Animales , Glucemia/análisis , Diabetes Mellitus Experimental/sangre , Diabetes Mellitus Tipo 1/sangre , Relación Dosis-Respuesta a Droga , Disruptores Endocrinos/farmacocinética , Monitoreo del Ambiente/métodos , Femenino , Hormonas Esteroides Gonadales/sangre , Nitratos/farmacocinética , Tamaño de los Órganos/efectos de los fármacos , Tiroxina/sangre , Triglicéridos/sangre , Contaminantes Químicos del Agua/farmacocinéticaRESUMEN
Environmental contamination resulting from the production or release of harmful chemicals can lead to negative consequences for wildlife and human health. Perfluorinated alkyl acids (PFAAs) were historically produced as protective coatings for many household items and currently persist in the environment, wildlife, and humans. PFAAs have been linked to immune suppression, endocrine disruption, and developmental toxicity in wildlife and laboratory studies. This study examines the American alligator, Alligator mississippiensis, as an important indicator of ecosystem contamination and a potential pathway for PFAA exposure in humans. Alligator meat harvested in the 2015 South Carolina (SC) public hunt season and prepared for human consumption was collected and analyzed for PFAAs to determine meat concentrations and relationships with animal body size (total length), sex, and location of harvest. Of the 15 PFAAs analyzed, perfluorooctane sulfonate (PFOS) was found in all alligator meat samples and at the highest concentrations (median 6.73ng/g). No relationship was found between PFAA concentrations and total length or sex. Concentrations of one or all compounds varied significantly across sampling locations, with alligators harvested in the Middle Coastal hunt unit having the highest PFOS concentrations (median 16.0ng/g; p=0.0001). Alligators harvested specifically from Berkley County, SC (located in the Middle Coastal hunt unit) had the highest PFOS concentrations and the greatest number of PFAAs detected (p<0.0001). The site-specific nature of PFAA concentrations in alligator meat observed in this study suggests a source of PFAA contamination in Berkley County, SC.
Asunto(s)
Caimanes y Cocodrilos/metabolismo , Monitoreo del Ambiente , Contaminantes Ambientales/metabolismo , Fluorocarburos/metabolismo , Ácidos Alcanesulfónicos/metabolismo , Animales , Disruptores Endocrinos/metabolismo , South CarolinaRESUMEN
Exposure to perfluorinated alkyl acids (PFAAs) has been linked to many harmful health effects including reproductive disorders, developmental delays, and altered liver and kidney function. Most human exposure to environmental contaminants, including PFAAs, occurs through consumption of contaminated food or drinking water. This study uses PFAA data from meat samples collected from recreationally harvested American alligators (Alligator mississippiensis) in South Carolina to assess potential dietary exposure of hunters and their families to PFAAs. Consumption patterns were investigated using intercept surveys of 23 hunters at a wild game meat processor. An exposure scenario using the average consumption frequency, portion size, and median perfluorooctane sulfonic acid (PFOS) concentration in alligator meat from all hunt units found the daily dietary exposure to be 2.11ng/kg body weight per day for an adult human. Dietary PFOS exposure scenarios based on location of harvest suggested the highest daily exposure occurs with alligator meat from the Middle Coastal hunt unit in South Carolina. Although no samples were found to exceed the recommended threshold for no consumption of PFOS found in Minnesota state guidelines, exposure to a mixture of PFAAs found in alligator meat and site-specific exposures based on harvest location should be considered in determining an appropriate guideline for vulnerable populations potentially exposed to PFAAs through consumption of wild alligator meat.
Asunto(s)
Caimanes y Cocodrilos/metabolismo , Exposición Dietética/estadística & datos numéricos , Contaminantes Ambientales/metabolismo , Fluorocarburos/metabolismo , Carne/análisis , Ácidos Alcanesulfónicos/metabolismo , Animales , Monitoreo del Ambiente , Contaminación de Alimentos/análisis , Humanos , South CarolinaRESUMEN
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that initiates a transcriptional pathway responsible for the expression of CYP1A subfamily members, key to the metabolism of xenobiotic compounds. Toxic planar halogenated aromatic hydrocarbons, including dioxin and PCBs, are capable of activating the AHR, and while dioxin and PCB inputs into the environment have been dramatically curbed following strict regulatory efforts in the United States, they persist in the environment and exposures remain relevant today. Little is known regarding the effects that long-term chronic exposures to dioxin or dioxin-like compounds might have on the development and subsequent health of offspring from exposed individuals, nor is much known regarding AHR expression in reptilians. Here, we characterize AHR and CYP1A gene expression in embryonic and juvenile specimen of a long-lived, apex predator, the American alligator (Alligator mississippiensis), and investigate variation in gene expression profiles in offspring collected from sites conveying differential exposures to environmental contaminants. Both age- and tissue-dependent patterning of AHR isoform expression are detected. We characterize two downstream transcriptional targets of the AHR, CYP1A1 and CYP1A2, and describe conserved elements of their genomic architecture. When comparisons across different sites are made, hepatic expression of CYP1A2, a direct target of the AHR, appears elevated in embryos from a site associated with a dioxin point source and previously characterized PCB contamination. Elevated CYP1A2 expression is not persistent, as site-specific variation was absent in juveniles originating from field-collected eggs but reared under lab conditions. Our results illustrate the patterning of AHR gene expression in a long-lived environmental model species, and indicate a potential contemporary influence of historical contamination. This research presents a novel opportunity to link contamination events to critical genetic pathways during embryonic development, and carries significant potential to inform our understanding of potential health effects in wildlife and humans.
Asunto(s)
Caimanes y Cocodrilos/fisiología , Citocromo P-450 CYP1A1/metabolismo , Monitoreo del Ambiente/métodos , Receptores de Hidrocarburo de Aril/metabolismo , Contaminación Química del Agua/estadística & datos numéricos , Caimanes y Cocodrilos/metabolismo , Animales , Citocromo P-450 CYP1A2/metabolismo , Dioxinas/metabolismo , Regulación de la Expresión Génica , Humanos , Hígado/metabolismo , Bifenilos Policlorados/metabolismo , Dibenzodioxinas Policloradas/metabolismoRESUMEN
Across diverse taxa, germ cell development is controlled by an intricate cascade of processes that are tightly controlled by the hypothalamic-pituitary-gonadal axis. Endocrine disturbances, such as those induced by endocrine disrupting chemicals (EDCs) can negatively affect spermatogenesis. Here, we investigate whether spermatogenesis is altered in the giant toad, Rhinella marina, living in agricultural areas where EDCs are used relative to suburban areas. We also ask if reductions in spermatogenesis were associated with developmental gonadal abnormalities (intersex) found in the same frogs. We found that toads in agricultural areas exhibited reduced spermatogenesis relative to non-agricultural animals, and that those reductions were not associated with gross gonadal abnormalities. All toads living in agricultural areas had reduced spermatogenesis relative to those living in non-agricultural areas regardless of whether they had gonadal abnormalities originating during development. Similarities in reproductive dysfunction among diverse taxa living in agricultural areas, including humans, suggest that many vertebrate taxa living in agricultural areas around the globe are likely experiencing some level of reproductive dysfunction.
Asunto(s)
Bufo marinus/fisiología , Disruptores Endocrinos/toxicidad , Monitoreo del Ambiente , Espermatogénesis/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Agricultura , AnimalesRESUMEN
Concentrations of mercury (Hg) are not well studied in free-ranging wildlife. Atmospheric deposition patterns of Hg have been studied in detail and have been modeled for both global and specific locations and often correlate to environmental impact. However, monitoring the impact of Hg deposition in wildlife is complicated due to local environmental conditions that can affect the transformation of atmospheric Hg to the biologically available forms (e.g., rainfall, humidity, pH, the ability of the environment to methylate Hg), as well as affect the accessibility to organisms for sampling. In this study, Hg concentrations in blood samples from a population of American alligators (Alligator mississippiensis) at Merritt Island National Wildlife Refuge (MINWR), FL, USA, over a seven-year period (2007 to 2014; n=174 individuals) were examined to assess Hg variation in the population, as well as the difference in Hg concentration as a function of health status. While most of this population is healthy, 18 individuals with low body mass indices (BMI, defined in this study) were captured throughout the sampling period. These alligators exhibited significantly elevated Hg concentrations compared to their age/sex/season matched counterparts with normal BMI, suggesting that health status should be taken into account when examining Hg concentrations and effects. Alligator blood Hg concentrations were related to the interaction of age/size, sex, and season. This study illustrates the value of a routinely monitored population of large predators in a unique coastal wetland ecosystem, and illuminates the value of long-term environmental exposure assessment.
Asunto(s)
Caimanes y Cocodrilos/sangre , Contaminantes Ambientales/sangre , Mercurio/sangre , Animales , Exposición a Riesgos Ambientales/análisis , Femenino , Florida , MasculinoRESUMEN
Endocrine disrupting contaminants, in combination with other environmental variables, are associated with altered reproductive health. Assisted reproductive technology (ART) procedures offer valuable opportunities to explore the connections between environmental contaminants in the ovarian microenvironment and measures of fertility, including impaired responsiveness to gonadotropins. Here, we investigate an emerging class of environmental contaminants, the perfluorinated alkyl acids (PFAAs), to determine whether ovarian contaminant levels are associated with measures of ovarian responsiveness and fertility outcomes in a South Carolina population of women undergoing ART. Levels of PFAAs in plasma and follicular fluid samples collected from women undergoing ovarian stimulation were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Six PFAAs were detected in both plasma and follicular fluid. PFAA concentrations in plasma correlate strongly to those detected in ovary and, with the exception of one compound, remain stable throughout ovarian stimulation. The concentration of PFHxS in follicular fluid inversely relates to baseline follicle counts. While no significant relationships were detected between ovarian response measures and PFAA concentrations, we identified a negative relationship between follicular fluid PFDA and PFuNA and blastocyst conversion rates. Our assessments indicate that plasma levels of PFAAs serve as a sound proxy of those in the ovarian compartment and that follicular fluid levels of specific PFAA compounds are inversely related to important clinical measures of reproductive health including baseline follicle count and post-fertilization success.
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Caprilatos/sangre , Caprilatos/química , Fluorocarburos/sangre , Fluorocarburos/química , Líquido Folicular/química , Ovario/efectos de los fármacos , Técnicas Reproductivas Asistidas , Adulto , Femenino , Humanos , South CarolinaRESUMEN
Routine monitoring of contaminant levels in wildlife is important for understanding chemical exposure and ultimately the link to ecosystem and human health. This is particularly important when the monitored species is recreationally hunted for human consumption. In the southeastern United States, recreational alligator harvesting takes place annually and in locations that are known to be contaminated with environmental pollutants. In this study, we investigated the biodistribution of trace elements in the American alligator (Alligator mississippiensis) from five sites in Florida, USA. These sites are locations where annual recreational alligator harvesting is permitted and two of the sites are identified as having high mercury contamination with human consumption advisories in effect. We utilized routinely collected monitoring samples (blood and scute), a commonly consumed tissue (muscle), and a classically analyzed tissue for environmental contaminants (liver) to demonstrate how the trace elements were distributed within the American alligator. We describe elemental tissue compartmentalization in an apex predator and investigate if noninvasive samples (blood and scute) can be used to estimate muscle tissue concentrations for a subset of elements measured. We found significant correlations for Hg, Rb, Se, Zn and Pb between noninvasive samples and consumed tissue and also found that Hg was the only trace metal of concern for this population of alligators. This study fills a gap in trace elemental analysis for reptilian apex predators in contaminated environments. Additionally, comprehensive elemental analysis of routinely collected samples can inform biomonitoring efforts and consumption advisories.
Asunto(s)
Caimanes y Cocodrilos/metabolismo , Oligoelementos/farmacocinética , Contaminantes Químicos del Agua/farmacocinética , Animales , Monitoreo del Ambiente , Florida , Distribución Tisular , Oligoelementos/análisis , Estados Unidos , Contaminantes Químicos del Agua/análisisRESUMEN
The American alligator, Alligator mississippiensis, like all crocodilians, has temperature-dependent sex determination, in which the sex of an embryo is determined by the incubation temperature of the egg during a critical period of development. The lack of genetic differences between male and female alligators leaves open the question of how the genes responsible for sex determination and differentiation are regulated. Insight into this question comes from the fact that exposing an embryo incubated at male-producing temperature to estrogen causes it to develop ovaries. Because estrogen response elements are known to regulate genes over long distances, a contiguous genome assembly is crucial for predicting and understanding their impact. We present an improved assembly of the American alligator genome, scaffolded with in vitro proximity ligation (Chicago) data. We use this assembly to scaffold two other crocodilian genomes based on synteny. We perform RNA sequencing of tissues from American alligator embryos to find genes that are differentially expressed between embryos incubated at male- versus female-producing temperature. Finally, we use the improved contiguity of our assembly along with the current model of CTCF-mediated chromatin looping to predict regions of the genome likely to contain estrogen-responsive genes. We find that these regions are significantly enriched for genes with female-biased expression in developing gonads after the critical period during which sex is determined by incubation temperature. We thus conclude that estrogen signaling is a major driver of female-biased gene expression in the post-temperature sensitive period gonads.
Asunto(s)
Caimanes y Cocodrilos/genética , Secuencia Conservada , Estrógenos/genética , Genoma , Transducción de Señal , Caimanes y Cocodrilos/embriología , Animales , Factor de Unión a CCCTC/metabolismo , Cromatina/metabolismo , Mapeo Contig , Estrógenos/metabolismo , Femenino , Masculino , Análisis de Secuencia de ADN , Procesos de Determinación del Sexo/genética , SinteníaRESUMEN
The present study aimed to quantitate 15 perfluoroalkyl acids (PFAAs) in 125 adult American alligators at 12 sites across the southeastern United States. Of those 15 PFAAs, 9 were detected in 65% to 100% of samples: perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), perfluorododecanoic acid, perfluorotridecanoic acid (PFTriA), perfluorotetradecanoic acid, perfluorohexanesulfonic acid (PFHxS), and perfluorooctane sulfonate (PFOS). Males (across all sites) showed significantly higher concentrations of 4 PFAAs: PFOS (p = 0.01), PFDA (p = 0.0003), PFUnA (p = 0.021), and PFTriA (p = 0.021). Concentrations of PFOS, PFHxS, and PFDA in plasma were significantly different among the sites in each sex. Alligators at both Merritt Island National Wildlife Refuge (FL, USA) and Kiawah Nature Conservancy (SC, USA) exhibited some of the highest PFOS concentrations (medians of 99.5 ng/g and 55.8 ng/g, respectively) in plasma measured to date in a crocodilian species. A number of positive correlations between PFAAs and snout-vent length were observed in both sexes, suggesting that PFAA body burdens increase with increasing size. In addition, several significant correlations among PFAAs in alligator plasma may suggest conserved sources of PFAAs at each site throughout the greater study area. The present study is the first to report PFAAs in American alligators, to reveal potential PFAA hot spots in Florida and South Carolina, and to provide a contaminant of concern when assessing anthropogenic impacts on ecosystem health. Environ Toxicol Chem 2017;36:917-925. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.
Asunto(s)
Ácidos Acíclicos/sangre , Caimanes y Cocodrilos/sangre , Ecosistema , Monitoreo del Ambiente/métodos , Fluorocarburos/sangre , Animales , Femenino , Florida , Islas , Masculino , South CarolinaRESUMEN
This study aimed to quantify concentrations of fifteen perfluoroalkyl acids (PFAAs) in the plasma of American alligators (Alligator mississippiensis) inhabiting wetlands surrounding the Kennedy Space Center (KSC) in Florida, USA located at Merritt Island National Wildlife Refuge (MINWR). Approximately 10 male and 10 female alligators (ntotal = 229) were sampled each month during 2008 and 2009 to determine if seasonal or spatial trends existed with PFAA burden. PFOS represented the highest plasma burden (median 185 ng/g) and PFHxS the second highest (median 7.96 ng/g). While no significant seasonal trends were observed, unique spatial trends emerged. Many of the measured PFAAs co-varied strongly together and similar trends were observed for PFOS, PFDA, PFUnA, and PFDoA, as well as for PFOA, PFHxS, PFNA, PFTriA, and PFTA, suggesting more than one source of PFAAs at MINWR. Higher concentrations of PFOS and the PFAAs that co-varied with PFOS were collected from animals around sites that included the Shuttle Landing Facility (SLF) fire house and the Neil Armstrong Operations and Checkout (O&C) retention pond, while higher concentrations of PFOA and the PFAA that co-varied with PFOA were sampled from animals near the gun range and the old fire training facility. Sex-based differences and snout-vent length (SVL) correlations with PFAA burden were also investigated.
Asunto(s)
Ácidos Alcanesulfónicos/sangre , Caimanes y Cocodrilos , Fluorocarburos/análisis , Animales , Animales Salvajes , Caprilatos/sangre , Ecosistema , Monitoreo del Ambiente/métodos , Femenino , Florida , Geografía , Islas , Masculino , Estaciones del Año , Contaminantes Químicos del Agua/análisisRESUMEN
Within the past few decades, the concept of endocrine-disrupting chemicals (EDCs) has risen from a position of total obscurity to become a focus of dialogue, debate, and concern among scientists, physicians, regulators, and the public. The emergence and development of this field of study has not always followed a smooth path, and researchers continue to wrestle with questions about the low-dose effects and nonmonotonic dose responses seen with EDCs, their biological mechanisms of action, the true pervasiveness of these chemicals in our environment and in our bodies, and the extent of their effects on human and wildlife health. This review chronicles the development of the unique, multidisciplinary field of endocrine disruption, highlighting what we have learned about the threat of EDCs and lessons that could be relevant to other fields. It also offers perspectives on the future of the field and opportunities to better protect human health.