The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Christine A. Bishop - One of the best experts on this subject based on the ideXlab platform.
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Organochlorine pesticides, PCBs, dibenzodioxin, and furan concentrations in Common Snapping Turtle eggs (Chelydra serpentina serpentina) in Akwesasne, Mohawk Territory, Ontario, Canada.
Archives of environmental contamination and toxicology, 2001Co-Authors: S. R. De Solla, Christine A. Bishop, H. Lickers, K. JockAbstract:Subsamples of eight clutches of Common Snapping Turtle eggs (Chelydra serpentina serpentina) were collected from four sites from the territory of the Mohawk Nation, Akwesasne, on the shore of the St. Lawrence River. Egg contents were analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), dibenzodioxins, and furans. The sites were 2 to 13 km downstream from PCB-contaminated landfill sites. Maximum concentrations of total PCBs in Snapping Turtle clutches were extremely high, and ranged from 2 378.2 ng/g to 737 683 ng/g (wet weight) and are among the highest recorded in any tissue of a free-ranging animal. Similarly, in a pooled sample of eggs from all four sites, the summed concentrations of non-ortho PCBs (n = 6 congeners) was also very high at 54.54 ng/g and the summed dioxin and furan concentrations (n = 11 congeners) was 85.8 ng/g. Sum organochlorine pesticide levels varied from 28 to 2,264 ng/g among the four sites. The levels of PCBs found in Turtle eggs exceed concentrations associated with developmental problems and reduced hatching success in Snapping Turtles and other species and also exceed the Canadian tissue residue guidelines for toxic equivalency concentrations. The extremely high levels of organochlorine contaminants demonstrate the high degree of contamination in the environment in the Akwesasne area.
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Effect of dichlorodiphenyltrichloroethane on sex determination of the Common Snapping Turtle (Chelydra serpentina serpentina).
Ecotoxicology and environmental safety, 1999Co-Authors: Melinda J. Portelli, Shane R. De Solla, Ronald J. Brooks, Christine A. BishopAbstract:Abstract Recent evidence indicates that 1,1,1-trichloro-2,2-bis( p -chlorophenyl)ethane (DDT) and some of its metabolites alter reproductive and endocrine function in wildlife. Exposure to such endocrine-disrupting compounds during embryonic development can affect sexual differentiation. The authors tested the hypothesis that dichlorodiphenyltrichloroethane ( p , p ′-DDE) causes feminization of the Common Snapping Turtle ( Chelydra s. serpentina ), a species with temperature-dependent sex determination, during embryonic development. Eggs from eight clutches (total eggs tested=237) were incubated at a male-producing temperature (26°C). At stage 14 of embryonic development, p , p ′-DDE was applied topically at four concentrations and estrogen (estradiol-17 β ) was applied as a positive control. Although application of estrogen did induce female development at this temperature, application of p , p ′-DDE did not affect sex determination at the exposure levels used. Residue analysis indicated that the amount of p , p ′-DDE detected in the eggs 72 h after application was considerably less than the concentrations applied. However, the amounts that penetrated the shells were comparable to levels which have been found in moderately contaminated sites in the Great Lakes. These results indicate that p , p ′-DDE, at levels that exist in the environment in the Great Lakes, does not cause the feminization of Snapping Turtles during embryonic development.
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Environmental contamination and developmental abnormalities in eggs and hatchlings of the Common Snapping Turtle (Chelydra serpentina serpentina) from the Great Lakes-St Lawrence River basin (1989-1991).
Environmental pollution (Barking Essex : 1987), 1998Co-Authors: Christine A. Bishop, K. E. Pettit, Sean W. Kennedy, J.j. Stegeman, Ross J. Norstrom, R. J. BrooksAbstract:Abstract During 1989–1991, we assessed developmental abnormalities in embryos and hatchlings from eggs of the Common Snapping Turtle (Chelydra serpentina serpentina). Eggs were collected and artificially incubated from eight sites in Ontario, Canada and Akwesasne/New York, USA. In eggs from the same clutches we measured 20 organochlorine pesticides, 48 polychlorinated biphenyl (PCBs) congeners including 6 non-ortho PCBs, 8 polychlorinated dibenzodioxins (PCDDs), 14 polychlorinated dibenzofurans (PCDFs) and total mercury. We found a significant increase in abnormal development with increasing polychlorinated aromatic hydrocarbon exposure in eggs, particularly PCDD and PCDF concentrations. In contrast, the risk of abnormality was not significantly higher as toxic equivalent concentrations increased in eggs. We also found significant 7-ethoxyresorufin O-deethylase and Cytochrome P4501A responses in livers of hatchling Turtles from Lake Ontario relative to hatchlings from a clean, inland site whereas we did not find any evidence of porphyria in the hatchlings from either site.
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temporal and geographic variation of organochlorine residues in eggs of the Common Snapping Turtle chelydra serpentina serpentina 1981 1991 and comparisons to trends in the herring gull larus argentatus in the great lakes basin in ontario canada
Archives of Environmental Contamination and Toxicology, 1996Co-Authors: Christine A. Bishop, Ross J. Norstrom, R. J. Brooks, K. E. PettitAbstract:Common Snapping Turtle (Chelydra serpentina serpentina) eggs from five sites within the Great Lakes basin, and from a reference site in north-central Ontario were collected during 1981–1991 and analyzed for four organochlorine pesticides, polychlorinated biphenyls (PCBs) including six non-ortho PCBs, polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). The pattern of geographic variation was consistent over time in eggs with Cootes Paradise/Hamilton Harbour and Lynde Creek eggs on Lake Ontario containing the highest concentrations and most PCDD and PCDF congeners among all sites. Eggs from Cranberry Marsh on Lake Ontario contained organochlorine concentrations similar to those from Big Creek Marsh and Rondeau Provincial Park on Lake Erie except PCDDs and PCDFs which occurred at higher concentrations and more congeners were detectable in Cranberry Marsh eggs.
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comparative study of contaminants in the mudpuppy amphibia and the Common Snapping Turtle reptilia st lawrence river canada
Archives of Environmental Contamination and Toxicology, 1995Co-Authors: J Bonin, Christine A. Bishop, Jeanluc Desgranges, Jean Rodrigue, A Gendron, John E. ElliottAbstract:Levels of organochlorine pesticides, polychlorinated biphenyl (PCB) congeners and mercury were measured in mudpuppy bodies, livers and gonads and in Snapping Turtle eggs to determine how the composition and concentration of these bioaccumulated contaminants differ between the two species. Furthermore, the geographic variation in contamination patterns were examined between the highly polluted St. Lawrence River and the much less polluted Ottawa River, Canada. Principal component analysis performed with 69 tissue samples (30 samples of mudpuppy tissues and 39 Turtle egg clutches) indicated distinct contamination patterns in the two species for PCB congeners; PCB congener composition in mudpuppies resembled the pattern reported for fish while the Turtle pattern was more akin to the bird pattern. This could be related to the metabolic capacity of each species. The organochlorine pesticide contamination profile was also species-specific although highly variable among locations. Contamination profiles were similar for mudpuppy gonads and carcasses but lipidweight basis concentrations were often a little higher in gonads. In both species, geographic variations in contamination patterns were noticeable and significant differences in contamination levels were detected between Ottawa River and St. Lawrence River samples. However, in both species, concentrations varied considerably within a single location. Sources of variability are discussed although the basic life history of these species in the St. Lawrence River system is relatively unknown.
Dane A. Crossley - One of the best experts on this subject based on the ideXlab platform.
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Draft Genome of the Common Snapping Turtle, Chelydra serpentina, a Model for Phenotypic Plasticity in Reptiles.
G3 (Bethesda Md.), 2020Co-Authors: Debojyoti Das, Dane A. Crossley, Sunil Kumar Singh, Jacob Bierstedt, Alyssa Erickson, Gina L. J. Galli, Turk RhenAbstract:Turtles are iconic reptiles that inhabit a range of ecosystems from oceans to deserts and climates from the tropics to northern temperate regions. Yet, we have little understanding of the genetic adaptations that allow Turtles to survive and reproduce in such diverse environments. Common Snapping Turtles, Chelydra serpentina, are an ideal model species for studying adaptation to climate because they are widely distributed from tropical to northern temperate zones in North America. They are also easy to maintain and breed in captivity and produce large clutch sizes, which makes them amenable to quantitative genetic and molecular genetic studies of traits like temperature-dependent sex determination. We therefore established a captive breeding colony and sequenced DNA from one female using both short and long reads. After trimming and filtering, we had 209.51Gb of Illumina reads, 25.72Gb of PacBio reads, and 21.72 Gb of Nanopore reads. The assembled genome was 2.258 Gb in size and had 13,224 scaffolds with an N50 of 5.59Mb. The longest scaffold was 27.24Mb. BUSCO analysis revealed 97.4% of core vertebrate genes in the genome. We identified 3.27 million SNPs in the reference Turtle, which indicates a relatively high level of individual heterozygosity. We assembled the transcriptome using RNA-Seq data and used gene prediction software to produce 22,812 models of protein coding genes. The quality and contiguity of the Snapping Turtle genome is similar to or better than most published reptile genomes. The genome and genetic variants identified here provide a foundation for future studies of adaptation to climate.
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Regulation of blood flow in the pulmonary and systemic circuits during submerged swimming in Common Snapping Turtle (Chelydra serpentina).
Journal of Experimental Biology, 2019Co-Authors: Amanda Reynolds Kirby, Brandt Smith, Dane A. CrossleyAbstract:Blood flow patterns and heart rate have rarely been investigated in freely swimming Turtles and their regulation during swimming is unknown. In this study, we investigated the blood flow patterns and heart rate in surfacing and during graded, submerged swimming activity in Common Snapping Turtles. We further investigated the effects of beta-adrenergic and cholinergic receptor blockade on blood flow and heart rate during these activities. Our findings illustrate that surfacing is accompanied by an increase in heart rate that is primarily due to beta-adrenergic stimulation. During swimming, this mechanism also increases heart rate while vagal withdrawal facilitates a systemic to pulmonary (left to right) shunt. The results indicate there may be important taxonomic effects on the responses of cardiac function to activity in Turtle species.
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Developmental plasticity of cardiac anoxia-tolerance in juvenile Common Snapping Turtles (Chelydra serpentina)
Proceedings. Biological sciences, 2019Co-Authors: Ilan M. Ruhr, Dane A. Crossley, Heather Mccourty, Afaf Bajjig, Holly A. Shiels, Gina L. J. GalliAbstract:For some species of ectothermic vertebrates, early exposure to hypoxia during embryonic development improves hypoxia-tolerance later in life. However, the cellular mechanisms underlying this phenomenon are largely unknown. Given that hypoxic survival is critically dependent on the maintenance of cardiac function, we tested the hypothesis that developmental hypoxia alters cardiomyocyte physiology in a manner that protects the heart from hypoxic stress. To test this hypothesis, we studied the Common Snapping Turtle, which routinely experiences chronic developmental hypoxia and exploits hypoxic environments in adulthood. We isolated cardiomyocytes from juvenile Turtles that embryonically developed in either normoxia (21% O2) or hypoxia (10% O2), and subjected them to simulated anoxia and reoxygenation, while simultaneously measuring intracellular Ca2+, pH and reactive oxygen species (ROS) production. Our results suggest developmental hypoxia improves cardiomyocyte anoxia-tolerance of juvenile Turtles, which is supported by enhanced myofilament Ca2+-sensitivity and a superior ability to suppress ROS production. Maintenance of low ROS levels during anoxia might limit oxidative damage and a greater sensitivity to Ca2+ could provide a mechanism to maintain contractile force. Our study suggests developmental hypoxia has long-lasting effects on Turtle cardiomyocyte function, which might prime their physiology for exploiting hypoxic environments.
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Developmental cardiovascular physiology of the olive ridley sea Turtle (Lepidochelys olivacea)
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2017Co-Authors: Dane A. Crossley, Janna Crossley, Camilla Smith, Martha Harfush, Hermilo Sánchez-sánchez, Mónica Vanessa Garduño-paz, José Fernando Méndez-sánchezAbstract:Our understanding of reptilian cardiovascular development and regulation has increased substantially for two species the American alligator (Alligator mississippiensis) and the Common Snapping Turtle (Chelydra serpentina) during the past two decades. However, what we know about cardiovascular maturation in many other species remains poorly understood or unknown. Embryonic sea Turtles have been studied to understand the maturation of metabolic function, but these studies have not addressed the cardiovascular system. Although prior studies have been pivotal in characterizing development, and factors that influence it, the development of cardiovascular function, which supplies metabolic function, is unknown in sea Turtles. During our investigation we focused on quantifying how cardiovascular morphological and functional parameters change, to provide basic knowledge of development in the olive ridley sea Turtle (Lepidochelys olivacea). Embryonic mass, as well as mass of the heart, lungs, liver, kidney, and brain increased during Turtle embryo development. Although heart rate was constant during this developmental period, arterial pressure approximately doubled. Further, while embryonic olive ridley sea Turtles lacked cholinergic tone on heart rate, there was a pronounced beta adrenergic tone on heart rate that decreased in strength at 90% of incubation. This beta adrenergic tone may be partially originating from the sympathetic nervous system at 90% of incubation, with the majority originating from circulating catecholamines. Data indicates that olive ridley sea Turtles share traits of embryonic functional cardiovascular maturation with the American alligator (Alligator mississippiensis) but not the Common Snapping Turtle (Chelydra serpentina).
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Developmental cardiovascular physiology of the olive ridley sea Turtle (Lepidochelys olivacea) Part A Molecular & integrative physiology
Comparative Biochemistry and Physiology, 2017Co-Authors: Dane A. Crossley, Janna Crossley, Camilla Smith, Martha Harfush, Hermilo Sánchez-sánchez, Mónica Vanessa Garduño-paz, José Fernando Méndez-sánchezAbstract:Our understanding of reptilian cardiovascular development and regulation has increased substantially for two species the American alligator (Alligator mississippiensis) and the Common Snapping Turtle (Chelydra serpentina) during the past two decades. However, what we know about cardiovascular maturation in many other species remains poorly understood or unknown. Embryonic sea Turtles have been studied to understand the maturation of metabolic function, but these studies have not addressed the cardiovascular system. Although prior studies have been pivotal in characterizing development, and factors that influence it, the development of cardiovascular function, which supplies metabolic function, is unknown in sea Turtles. During our investigation we focused on quantifying how cardiovascular morphological and functional parameters change, to provide basic knowledge of development in the olive ridley sea Turtle (Lepidochelys olivacea). Embryonic mass, as well as mass of the heart, lungs, liver, kidney, and brain increased during Turtle embryo development. Although heart rate was constant during this developmental period, arterial pressure approximately doubled. Further, while embryonic olive ridley sea Turtles lacked cholinergic tone on heart rate, there was a pronounced beta adrenergic tone on heart rate that decreased in strength at 90% of incubation. This beta adrenergic tone may be partially originating from the sympathetic nervous system at 90% of incubation, with the majority originating from circulating catecholamines. Data indicates that olive ridley sea Turtles share traits of embryonic functional cardiovascular maturation with the American alligator (Alligator mississippiensis) but not the Common Snapping Turtle (Chelydra serpentina).
Turk Rhen - One of the best experts on this subject based on the ideXlab platform.
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Draft Genome of the Common Snapping Turtle, Chelydra serpentina, a Model for Phenotypic Plasticity in Reptiles.
G3 (Bethesda Md.), 2020Co-Authors: Debojyoti Das, Dane A. Crossley, Sunil Kumar Singh, Jacob Bierstedt, Alyssa Erickson, Gina L. J. Galli, Turk RhenAbstract:Turtles are iconic reptiles that inhabit a range of ecosystems from oceans to deserts and climates from the tropics to northern temperate regions. Yet, we have little understanding of the genetic adaptations that allow Turtles to survive and reproduce in such diverse environments. Common Snapping Turtles, Chelydra serpentina, are an ideal model species for studying adaptation to climate because they are widely distributed from tropical to northern temperate zones in North America. They are also easy to maintain and breed in captivity and produce large clutch sizes, which makes them amenable to quantitative genetic and molecular genetic studies of traits like temperature-dependent sex determination. We therefore established a captive breeding colony and sequenced DNA from one female using both short and long reads. After trimming and filtering, we had 209.51Gb of Illumina reads, 25.72Gb of PacBio reads, and 21.72 Gb of Nanopore reads. The assembled genome was 2.258 Gb in size and had 13,224 scaffolds with an N50 of 5.59Mb. The longest scaffold was 27.24Mb. BUSCO analysis revealed 97.4% of core vertebrate genes in the genome. We identified 3.27 million SNPs in the reference Turtle, which indicates a relatively high level of individual heterozygosity. We assembled the transcriptome using RNA-Seq data and used gene prediction software to produce 22,812 models of protein coding genes. The quality and contiguity of the Snapping Turtle genome is similar to or better than most published reptile genomes. The genome and genetic variants identified here provide a foundation for future studies of adaptation to climate.
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Incubation temperature and satiety influence general locomotor and exploratory behaviors in the Common Snapping Turtle (Chelydra serpentina).
Physiology & behavior, 2020Co-Authors: Soleille Miller, Adam Derenne, Susan N. Ellis-felege, Turk RhenAbstract:Temperature during embryogenesis determines sex and has been shown to influence other physiological traits in reptiles. The Common Snapping Turtle (Chelydra serpentina) is an ideal model for testing how temperature impacts behavior in species that display temperature-dependent sex determination. Behavioral assays are crucial to understanding how a changing climate may affect whole organism function in the Snapping Turtle. Currently, there are few behavioral assays for semi-aquatic vertebrates like Turtles. In this study, we used digital cameras to record behavior of fed and fasted hatchling Turtles from different incubation temperatures in an open field setting for 20 min in 2018 and repeated the experiment in 2019. Open fields were circular tanks filled with water to a depth of 3.5 cm. Each field was split into four quadrants and two zones (inner and outer). The amount of time Turtles spent actively moving, total distance travelled, and several other measures were collected and summarized automatically from videos with open source image analysis software (ImageJ). Satiety and incubation temperature had significant effects on total distance moved, time spent moving, and time moving in the outer zone. These findings indicate that temperature during embryogenesis has a long-lasting effect on neural mechanisms underlying exploratory or general locomotor behavior in Turtles.
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Role for androgens in determination of ovarian fate in the Common Snapping Turtle, Chelydra serpentina.
General and comparative endocrinology, 2019Co-Authors: Anthony L. Schroeder, Turk RhenAbstract:Abstract Sex steroids are involved in sex determination in almost all vertebrates, including species with temperature-dependent sex determination (TSD). It is well established that aromatase and estrogens are involved in ovary determination in TSD species. In contrast, the role of non-aromatizable androgens in TSD is less clear. In this study, we used dihydrotestosterone (DHT) and an antagonist of the mammalian androgen receptor (flutamide) to examine the impact of androgens on sex determination in the Snapping Turtle. We incubated eggs at a male-producing temperature and treated embryos with drug delivery vehicle (5 L ethanol), DHT in vehicle, or flutamide in vehicle during the sex-determining period. We then measured expression of markers for ovarian and testicular development and genes involved in steroidogenesis. A subset of embryos and hatchlings were collected for histological analysis of gonad differentiation and sex determination. DHT and flutamide both induced ovarian development: 100% of vehicle-treated hatchlings had testes, while 60% of DHT-treated and 32% flutamide-treated hatchlings had ovaries. DHT and flutamide treatments also had feminizing effects on gene expression patterns and the structure of embryonic gonads. DHT treatment increased expression of FoxL2, androgen receptor, aromatase and several steroidogenic genes. Flutamide produced a similar, but weaker, pattern of gene expression. Genes involved in testis development (Sox9 and Amh) were influenced by flutamide treatment. Our findings support the hypothesis that androgens and the androgen receptor are involved in ovary determination in the Common Snapping Turtle.
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Characterization of the FoxL2 proximal promoter and coding sequence from the Common Snapping Turtle (Chelydra serpentina).
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2017Co-Authors: Lei Guo, Turk RhenAbstract:Abstract Sex is determined by temperature during embryogenesis in Snapping Turtles, Chelydra serpentina . Previous studies in this species show that dihydrotestosterone (DHT) induces ovarian development at temperatures that normally produce males or mixed sex ratios. The feminizing effect of DHT is associated with increased expression of FoxL2, suggesting that androgens regulate transcription of FoxL2. To test this hypothesis, we cloned the proximal promoter (1.6 kb) and coding sequence for Snapping Turtle FoxL2 (tFoxL2) in frame with mCherry to produce a fluorescent reporter. The tFoxL2-mCherry fusion plasmid or mCherry control plasmid were stably transfected into mouse KK1 granulosa cells. These cells were then treated with 0, 1, 10, or 100 nM DHT to assess androgen effects on tFoxL2-mCherry expression. In contrast to the main hypothesis, DHT did not alter expression of the tFoxL2-mCherry reporter. However, normal serum increased expression of tFoxL2-mCherry when compared to charcoal-stripped serum, indicating that the cloned region of tFoxL2 contains cis regulatory elements. We also used the tFoxL2-mCherry plasmid as an expression vector to test the hypothesis that DHT and tFoxL2 interact to regulate expression of endogenous genes in granulosa cells. While tFoxL2-mCherry and DHT had independent effects on mouse FoxL2, FshR, GnRHR, and StAR expression, tFoxL2-mCherry potentiated low concentration DHT effects on mouse aromatase expression. Further studies will be required to determine whether synergistic regulation of aromatase by DHT and FoxL2 also occurs in Turtle gonads during the sex-determining period, which would explain the feminizing effect of DHT in this species.
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A Novel Candidate Gene for Temperature-Dependent Sex Determination in the Common Snapping Turtle.
Genetics, 2016Co-Authors: Anthony Schroeder, Kelsey J. Metzger, Alexandra Miller, Turk RhenAbstract:Temperature-dependent sex determination (TSD) was described nearly 50 years ago. Researchers have since identified many genes that display differential expression at male- vs. female-producing temperatures. Yet, it is unclear whether these genes (1) are involved in sex determination per se, (2) are downstream effectors involved in differentiation of ovaries and testes, or (3) are thermo-sensitive but unrelated to gonad development. Here we present multiple lines of evidence linking CIRBP to sex determination in the Snapping Turtle, Chelydra serpentina We demonstrate significant associations between a single nucleotide polymorphism (SNP) (c63A > C) in CIRBP, transcript levels in embryonic gonads during specification of gonad fate, and sex in hatchlings from a thermal regime that produces mixed sex ratios. The A allele was induced in embryos exposed to a female-producing temperature, while expression of the C allele did not differ between female- and male-producing temperatures. In accord with this pattern of temperature-dependent, allele-specific expression, AA homozygotes were more likely to develop ovaries than AC heterozygotes, which, in turn, were more likely to develop ovaries than CC homozygotes. Multiple regression using SNPs in CIRBP and adjacent loci suggests that c63A > C may be the causal variant or closely linked to it. Differences in CIRBP allele frequencies among Turtles from northern Minnesota, southern Minnesota, and Texas reflect small and large-scale latitudinal differences in TSD pattern. Finally, analysis of CIRBP protein localization reveals that CIRBP is in a position to mediate temperature effects on the developing gonads. Together, these studies strongly suggest that CIRBP is involved in determining the fate of the bipotential gonad.
John E. Elliott - One of the best experts on this subject based on the ideXlab platform.
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comparative study of contaminants in the mudpuppy amphibia and the Common Snapping Turtle reptilia st lawrence river canada
Archives of Environmental Contamination and Toxicology, 1995Co-Authors: J Bonin, Christine A. Bishop, Jeanluc Desgranges, Jean Rodrigue, A Gendron, John E. ElliottAbstract:Levels of organochlorine pesticides, polychlorinated biphenyl (PCB) congeners and mercury were measured in mudpuppy bodies, livers and gonads and in Snapping Turtle eggs to determine how the composition and concentration of these bioaccumulated contaminants differ between the two species. Furthermore, the geographic variation in contamination patterns were examined between the highly polluted St. Lawrence River and the much less polluted Ottawa River, Canada. Principal component analysis performed with 69 tissue samples (30 samples of mudpuppy tissues and 39 Turtle egg clutches) indicated distinct contamination patterns in the two species for PCB congeners; PCB congener composition in mudpuppies resembled the pattern reported for fish while the Turtle pattern was more akin to the bird pattern. This could be related to the metabolic capacity of each species. The organochlorine pesticide contamination profile was also species-specific although highly variable among locations. Contamination profiles were similar for mudpuppy gonads and carcasses but lipidweight basis concentrations were often a little higher in gonads. In both species, geographic variations in contamination patterns were noticeable and significant differences in contamination levels were detected between Ottawa River and St. Lawrence River samples. However, in both species, concentrations varied considerably within a single location. Sources of variability are discussed although the basic life history of these species in the St. Lawrence River system is relatively unknown.
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Environmental Contaminants in Eggs of the Common Snapping Turtle (Chelydra serpentina serpentina) from the Great Lakes-St. Lawrence River Basin of Ontario, Canada (1981, 1984)
Journal of Great Lakes Research, 1993Co-Authors: John Struger, Martyn E. Obbard, Christine A. Bishop, Ross J. Norstrom, John E. Elliott, D.v. Weseloh, M. SimonAbstract:Abstract Common Snapping Turtle eggs were collected at nesting sites from two locations in 1981 and eight locations in 1984 in Ontario, Canada, and analyzed for chlorinated hydrocarbons. Nine locations were within the Great Lakes-St. Lawrence River basin and one location, Algonquin Provincial Park, served as a control site outside the basin. Total PCBs ranged from 0.057 to 4.76 mg/kg (wet wt.) among the Great Lakes-St. Lawrence River samples. Mean total PCB concentration at Algonquin Park was 0.187 mg/kg. Eggs from Hamilton Harbour, Port Franks, Bay of Quinte/Murray Canal, and Lake St. Clair were the most contaminated among the ten sample locations. There was statistically significant variation in concentrations of all organochlorine compounds among sites. In some locations, there was high variation in contamination among clutches. A pool of eggs from Hamilton Harbour contained 67 ng/kg of 2378-tetrachlorodibenzo-p-dioxin and 14.0 ng/kg of23478-pentachlorodibenzofuran. Some dioxin congeners were present in Turtle eggs at concentrations higher or equal to that in herring gull eggs from Hamilton Harbour. Comprehensive GC/MS analysis of the Hamilton Harbour eggs also revealed the presence of trace amounts of o,p-dicofol, octachlorostyrene, and toxaphene. Geographic variation in contaminant levels in Snapping Turtle eggs from wetlands is similar to that in spottail shiners and herring gull eggs collected in the pelagic zone of the Great Lakes. This may be due to the consumption of migrant fish by Snapping Turtles in nearshore wetlands.
John Eme - One of the best experts on this subject based on the ideXlab platform.
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phenotypic plasticity in the Common Snapping Turtle chelydra serpentina long term physiological effects of chronic hypoxia during embryonic development
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2016Co-Authors: Oliver H. Wearing, Turk Rhen, John Eme, Dane A. CrossleyAbstract:Studies of embryonic and hatchling reptiles have revealed marked plasticity in morphology, metabolism, and cardiovascular function following chronic hypoxic incubation. However, the long-term effects of chronic hypoxia have not yet been investigated in these animals. The aim of this study was to determine growth and postprandial O2 consumption (Vo2), heart rate (fH), and mean arterial pressure (Pm, in kPa) of Common Snapping Turtles (Chelydra serpentina) that were incubated as embryos in chronic hypoxia (10% O2, H10) or normoxia (21% O2, N21). We hypothesized that hypoxic development would modify posthatching body mass, metabolic rate, and cardiovascular physiology in juvenile Snapping Turtles. Yearling H10 Turtles were significantly smaller than yearling N21 Turtles, both of which were raised posthatching in normoxic, Common garden conditions. Measurement of postprandial cardiovascular parameters and O2 consumption were conducted in size-matched three-year-old H10 and N21 Turtles. Both before and 12 h after feeding, H10 Turtles had a significantly lower fH compared with N21 Turtles. In addition, Vo2 was significantly elevated in H10 animals compared with N21 animals 12 h after feeding, and peak postprandial Vo2 occurred earlier in H10 animals. Pm of three-year-old Turtles was not affected by feeding or hypoxic embryonic incubation. Our findings demonstrate that physiological impacts of developmental hypoxia on embryonic reptiles continue into juvenile life.
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Phenotypic plasticity in the Common Snapping Turtle (Chelydra serpentina): Long-term physiological effects of chronic hypoxia during embryonic development.
American journal of physiology. Regulatory integrative and comparative physiology, 2015Co-Authors: Oliver H. Wearing, Turk Rhen, John Eme, Dane A. CrossleyAbstract:Studies of embryonic and hatchling reptiles have revealed marked plasticity in morphology, metabolism, and cardiovascular function following chronic hypoxic incubation. However, the long-term effec...
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Critical Windows of Cardiovascular Susceptibility to Developmental Hypoxia in Common Snapping Turtle (Chelydra serpentina) Embryos.
Physiological and biochemical zoology : PBZ, 2014Co-Authors: Kevin B. Tate, Turk Rhen, Zachary F. Kohl, John Eme, Dane A. CrossleyAbstract:AbstractEnvironmental conditions fluctuate dramatically in some reptilian nests. However, critical windows of environmental sensitivity for cardiovascular development have not been identified. Continuous developmental hypoxia has been shown to alter cardiovascular form and function in embryonic Snapping Turtles (Chelydra serpentina), and we used this species to identify critical periods during which hypoxia modifies the cardiovascular phenotype. We hypothesized that incubation in 10% O2 during specific developmental periods would have differential effects on the cardiovascular system versus overall somatic growth. Two critical windows were identified with 10% O2 from 50% to 70% of incubation, resulting in relative heart enlargement, either via preservation of or preferential growth of this tissue, while exposure to 10% O2 from 20% to 70% of incubation resulted in a reduction in arterial pressure. The deleterious or advantageous aspects of these embryonic phenotypes in posthatching Snapping Turtles have ye...