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Christine A. Bishop - One of the best experts on this subject based on the ideXlab platform.
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contaminant residues in Snapping Turtle chelydra s serpentina eggs from the great lakes st lawrence river basin 1999 to 2000
Archives of Environmental Contamination and Toxicology, 2004Co-Authors: S L Ashpole, Christine A. Bishop, Ronald J. BrooksAbstract:To determine temporal and geographic variations of environmentally persistent pollutants, the concentrations of several contaminants were measured in Snapping Turtle eggs in 1999 and 2000. Contaminants included polychlorinated biphenyls (PCBs), non-ortho PCBs, polychlorinated dibenzodioxins and furans, organochlorine pesticides, and total mercury. Egg collection sites within the St. Lawrence Area of Concern (AOC) and the Territory of Akwesasne included Turtle Creek, Snye Marsh, and Raquette River. Additional contaminated sites were Gray’s Creek (within the St. Lawrence AOC boundary), Coote’s Paradise (Hamilton Harbour AOC), and the Territory of Walpole Island (St. Clair AOC). Reference sites were Lake Sasajewun, Algonquin Provincial Park in central Ontario, and in close proximity to the St. Lawrence Area AOC, Hoasic Creek and Cooper Marsh. Eggs from clutches collected from Akwesasne contained the highest concentrations of contaminants. Mean total PCB concentrations for Akwesasne clutches ranged from 1,900 to 61,000 ng/g wet weight (w.w.), which was 360 to 3,100 times higher than the mean concentrations at the reference sites. The high levels of contaminants in eggs, from sites within Akwesasne, were consistent with trends reported in the past and reflect the influence of the proximity of heavy industry. Current contaminant concentrations in clutches from Coote’s Paradise are comparable with those recorded in 1989 and 1990 but are 200 to 800 times lower than concentrations reported in 1984 and 1988. Eggs from Lake Sasajewun contained relatively low contaminant levels, which is consistent with atmospheric deposition. Our results support that Snapping Turtles are good indicators of temporal and geographic contaminant trends.
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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.
Arthur Georges - One of the best experts on this subject based on the ideXlab platform.
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on a razor s edge status and prospects of the critically endangered bellinger river Snapping Turtle myuchelys georgesi
Aquatic Conservation-marine and Freshwater Ecosystems, 2020Co-Authors: Bruce C Chessman, Gerry Mcgilvray, Shane Ruming, Hugh Jones, Kristen Petrov, Darren Fielder, Rickyjohn Spencer, Arthur GeorgesAbstract:In the summer and autumn of 2015, the Bellinger River Snapping Turtle (Myuchelys georgesi), a narrow‐range endemic of eastern New South Wales, Australia, suffered mass mortality from epidemic disease, apparently caused by a previously unknown virus. Information on the current population size and structure of M. georgesi, and the body condition and growth of the surviving individuals, is needed to support planning of conservation actions. Population estimates are also needed for a sympatric population of the widely distributed Macquarie Turtle (Emydura macquarii), which has probably been introduced to the Bellinger River and may threaten the persistence of M. georgesi through hybridization, competition, and disease transmission. Data from five Turtle surveys between November 2015 and November 2018 were used to estimate populations of the two species in the Bellinger River by an analysis based on habitat extent and Turtle detectability. Changes in the body condition of M. georgesi and the body growth of both species were also assessed. Current populations of ~150 M. georgesi and ~500 E. macquarii are indicated, although the uncertainty of these estimates is high. The estimate for M. georgesi represents a decline of >90% from the historical population. Moreover, about 88% of the surviving M. georgesi are immature, and only about 5% are mature females. However, the body condition of the survivors has improved recently. Growth models suggest that M. georgesi matures later than E. macquarii, which may provide the latter with a competitive advantage. Evidence presented here does not support a previous hypothesis that M. georgesi were predisposed to disease through malnutrition and consequently reduced immune competence caused by high water temperatures and low river flows. Continuing disease, hybridization, and interspecific competition are probably the greatest threats to the persistence of the species.
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contemporary genetic structure reflects historical drainage isolation in an australian Snapping Turtle elseya albagula
Zoological Journal of the Linnean Society, 2013Co-Authors: Erica V. Todd, David Blair, Colin J. Limpus, Sharon Farley, Lachlan Farrington, Nancy N Fitzsimmons, Arthur Georges, Dean R. JerryAbstract:Effective spatial classification of freshwater biodiversity remains a worldwide conservation challenge. The isolating nature of catchment boundaries over evolutionary timescales makes them potentially important in defining natural units for biodiversity management. We sought to clarify biogeographical relationships amongst drainages within Australia's biodiverse mid-eastern coastal region (Fitzroy, Burnett, and Mary Catchments) where freshwater communities face considerable urban pressure, using a locally endemic riverine specialist, the white-throated Snapping Turtle, Elseya albagula. Mitochondrial and nuclear microsatellite data sets were employed to investigate past and present influences on population connectivity and to identify units for management. Populations within catchments were largely well connected genetically. However, the Fitzroy Catchment contained a distinct genetic lineage, deeply divergent from a second lineage present across the Burnett and Mary Catchments. The two lineages can be considered evolutionarily significant units that reflect historical isolation of the Fitzroy and recent coalescence of the Burnett-Mary Catchments during lowered Pleistocene sea levels. Congruence with geological evidence and patterns reported for fish and macroinvertebrates supports a shared biogeographical history of a diverse regional biota. This work highlights the need for better spatial classification of freshwater biodiversity at local as well as regional scales, including recognition of potentially cryptic diversity amongst individual river drainages.
Ronald J. Brooks - One of the best experts on this subject based on the ideXlab platform.
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biology of the Snapping Turtle chelydra serpentina
2008Co-Authors: Anthony C Steyermark, Michael S Finkler, Ronald J. BrooksAbstract:The name "Snapping Turtle" conjures up images of powerful, prehistoric-looking beasts that lurk in the dark waters of local swimming holes. Beyond its status as childhood legend, Chelydra serpentina is one of the most interesting reptiles of the New World. One of our largest Turtles, this animal weighs up to thirty-five pounds, lays as many as one hundred eggs and can deliver a nasty bite. Due to its wide distribution, abundance, and large reproductive output, the Snapping Turtle has become one of the most extensively studied species of reptiles. This volume synthesizes all that is known about the common Snapping Turtle to provide an up-to-date and comprehensive resource on the species' evolution, physiology, behavior, and life history. Anthony C. Steyermark, Michael S. Finkler, Ronald J. Brooks, and a team of experts detail the systematics, energetics, growth patterns, sex determination, and population genetics of Snapping Turtles and devote special attention to the fossil record of the Snapping Turtle family Chelydridae. The first broad biological treatment of the common Snapping Turtle, this is the definitive reference for anyone working with or interested in this fascinating reptile. Contributors: Ralph A. Ackerman, Iowa State University; Abdulaziz Y. A. AlKindi, Sultan Qaboos University; Barbara A. Bell, Drexel University; Ronald J. Brooks, University of Guelph; Justin D. Congdon, Savannah River Ecology Lab; Carl H. Ernst, George Mason University; Michael A. Ewert, Indiana University Bloomington; Michael S. Finkler, Indiana University Kokomo; Matthew K. Fujita, University of California, Davis; Eugene S. Gaffney, American Museum of Natural History; David A. Galbraith, Royal Botanical Gardens; Robert E. Gatten, Jr., University of North Carolina at Greensboro; Judith L. Greene, Savannah River Ecology Lab; J. Howard Hutchison, University of California, Berkeley; John B. Iverson, Earlham College; Fredric J. Janzen, Iowa State University; Jason J. Kolbe, Washington University; David B. Lott, Clarion University of Pennsylvania; Ibrahim Y. Mahmoud, Sultan Qaboos University; Don Moll, Southwest Missouri State University; Scott A. Reese, Kennesaw State University; Todd A. Rimkus, Marymount University; H. Bradley Shaffer, University of California Davis; James R. Spotila, Drexel University; David E. Starkey, University of Central Arkansas; Anthony C. Steyermark, University of St. Thomas; Gordon R. Ultsch, University of Alabama; Nigel H. West, University of Saskatchewan
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contaminant residues in Snapping Turtle chelydra s serpentina eggs from the great lakes st lawrence river basin 1999 to 2000
Archives of Environmental Contamination and Toxicology, 2004Co-Authors: S L Ashpole, Christine A. Bishop, Ronald J. BrooksAbstract:To determine temporal and geographic variations of environmentally persistent pollutants, the concentrations of several contaminants were measured in Snapping Turtle eggs in 1999 and 2000. Contaminants included polychlorinated biphenyls (PCBs), non-ortho PCBs, polychlorinated dibenzodioxins and furans, organochlorine pesticides, and total mercury. Egg collection sites within the St. Lawrence Area of Concern (AOC) and the Territory of Akwesasne included Turtle Creek, Snye Marsh, and Raquette River. Additional contaminated sites were Gray’s Creek (within the St. Lawrence AOC boundary), Coote’s Paradise (Hamilton Harbour AOC), and the Territory of Walpole Island (St. Clair AOC). Reference sites were Lake Sasajewun, Algonquin Provincial Park in central Ontario, and in close proximity to the St. Lawrence Area AOC, Hoasic Creek and Cooper Marsh. Eggs from clutches collected from Akwesasne contained the highest concentrations of contaminants. Mean total PCB concentrations for Akwesasne clutches ranged from 1,900 to 61,000 ng/g wet weight (w.w.), which was 360 to 3,100 times higher than the mean concentrations at the reference sites. The high levels of contaminants in eggs, from sites within Akwesasne, were consistent with trends reported in the past and reflect the influence of the proximity of heavy industry. Current contaminant concentrations in clutches from Coote’s Paradise are comparable with those recorded in 1989 and 1990 but are 200 to 800 times lower than concentrations reported in 1984 and 1988. Eggs from Lake Sasajewun contained relatively low contaminant levels, which is consistent with atmospheric deposition. Our results support that Snapping Turtles are good indicators of temporal and geographic contaminant trends.
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octylphenol op alters the expression of members of the amyloid protein family in the hypothalamus of the Snapping Turtle chelydra serpentina serpentina
Environmental Health Perspectives, 2002Co-Authors: Vance L Trudeau, Sean W. Kennedy, Suzanne Chiu, Ronald J. BrooksAbstract:The gonadal estrogen estradiol-17beta (E(2)) is important for developing and regulating hypothalamic function and many aspects of reproduction in vertebrates. Pollutants such as octylphenol (OP) that mimic the actions of estrogens are therefore candidate endocrine-disrupting chemicals. We used a differential display strategy (RNA-arbitrarily primed polymerase chain reaction) to isolate partial cDNA sequences of neurotransmitter, developmental, and disease-related genes that may be regulated by OP or E(2) in the Snapping Turtle Chelydra serpentina serpentina hypothalamus. Hatchling and year-old male Snapping Turtles were exposed to a 10 ng/mL nominal concentration of waterborne OP or E(2) for 17 days. One transcript [421 base pairs (bp)] regulated by OP and E(2) was 93% identical to human APLP-2. APLP-2 and the amyloid precursor protein (APP) regulate neuronal differentiation and are also implicated in the genesis of Alzheimer disease in humans. Northern blot analysis determined that the Turtle hypothalamus contains a single APLP-2 transcript of 3.75 kb in length. Exposure to OP upregulated hypothalamic APLP-2 mRNA levels 2-fold (p < 0.05) in month-old and yearling Turtles. E(2) did not affect APLP-2 mRNA levels in hatchlings but stimulated a 2-fold increase (p < 0.05) in APLP-2 mRNA levels in yearling males. The protein beta-amyloid, a selectively processed peptide derived from APP, is also involved in neuronal differentiation, and accumulation of this neurotoxic peptide causes neuronal degeneration in the brains of patients with Alzheimer disease. Therefore, we also sought to determine the effects of estrogens on the expression of beta-amyloid. Using homology cloning based on known sequences, we isolated a cDNA fragment (474 bp) from Turtle brain with 88% identity to human APP. Northern blot analysis determined that a single 3.5-kb transcript was expressed in the Turtle hypothalamus. Waterborne OP also increased the expression of hypothalamic APP after 35 days of exposure. Our results indicate that low levels of OP are bioactive and can alter the expression of APLP-2 and APP. Because members of the APP gene family are involved in neuronal development, we hypothesize that OP exposure may disrupt hypothalamic development in young Turtles.
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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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Chlorinated hydrocarbons in early life stages of the common Snapping Turtle (Chelydra serpentina serpentina) from a coastal wetland on lake Ontario, Canada
Environmental Toxicology and Chemistry, 1995Co-Authors: Christine A. Bishop, David R. S. Lean, John H. Carey, Ronald J. BrooksAbstract:To assess intra-clutch variation in contaminant concentrations in eggs, and to investigate the dynamics of chlorinated hydrocarbon accumulation in embryos of the common Snapping Turtle (Chelydra serpentina), concentrations of p,p DDE, hexachlorobenzene, trans nonachlor, cis-chlordane, and six PCB congeners were measured in eggs, embryos, and hatchhngs Samples were collected from Cootes Paradise, a wetland at the western end of Lake Ontario, Ontario, Canada The intra-clutch variation in chlorinated hydrocarbon concentrations within four Snapping Turtle clutches was determined by analyzing the first, last, and middle five eggs oviposited in the nest The first five eggs had the highest mean concentrations of all chlorinated hydrocarbons (wet weight basis), wet weight, and egg diameter On a lipid weight basis, the first five eggs contained the highest concentration of all compounds except total PCBs and cis chlordane The concentration of as chlordane (lipid weight basis) was the only parameter measured that was significantly different among the three sets of eggs At hatching, Snapping Turtles without yolk sacs contained from 55 2 to 90 5% of the absolute amount of organochlorine compounds measured in the egg at oviposition Eighteen days after hatching, the body burden of PCBs and pesticides decreased to 45 3 to 62 2% of that in the fresh egg The accumulation of organochlorine chemicals in embryonic Turtles peaked at or just before hatching and then declined thereafter, which is consistent with trends reported in developing sea Turtles, fish, and birds
Una Ryan - One of the best experts on this subject based on the ideXlab platform.
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Further characterisation of Haemocystidium chelodinae-like Haemoproteidae isolated from the Bellinger River Snapping Turtle (Myuchelys georgesi)
Parasitology Research, 2020Co-Authors: Jill M. Austen, Jane Hall, Alireza Zahedi, Alexander Goften, Una RyanAbstract:The Bellinger River Snapping Turtle ( Myuchelys georgesi ) is endemic to Australia and is confined to a highly restricted distribution in the Bellinger River in New South Wales. Routine veterinary health examinations of 17 healthy Turtles were undertaken, along with the collection and analysis of blood samples, during conservation efforts to save the species following a catastrophic population decline. Microscopy analysis of blood films detected Haemoproteidae parasites that morphologically resembled Haemocystidium chelodinae inside Turtle erythrocytes. Of the 17 Turtles examined, 16 were positive for infection with H. chelodinae by both light microscopy and PCR. DNA sequencing of a partial fragment of the mitochondrial cytochrome b ( cytb ) gene and phylogenetic analysis identified two different H. chelodinae- like genotypes. The phylogenetic relationship of H. chelodinae -like to other Haemoproteidae species based on cytb sequences grouped H. chelodinae -like into the reptile clade, but revealed the Haemocystidium genus to be paraphyletic as the clade also contained Haemoproteus , thus supporting a re-naming of Haemoproteus species from reptiles to Haemocystidium species . This study reports for the first time the genetic characterisation of H. chelodinae -like organisms isolated from a new Testudine host species, the Bellinger River Snapping Turtle. As evidence grows, further research will be necessary to understand the mode of transmission and to investigate whether these parasites are pathogenic to their hosts.
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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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.
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molecular and morphological differentiation of testes and ovaries in relation to the thermosensitive period of gonad development in the Snapping Turtle chelydra serpentina
Differentiation, 2015Co-Authors: Turk Rhen, Dane A. Crossley, Anthony L Schroeder, Ruby Fagerlie, Jeffrey W. LangAbstract:Ambient temperatures during embryonic development determine gonadal sex in many reptiles. The temperature sensitive period for sex determination has been defined by shifting eggs between female- and male-producing temperatures in a few species. This phase spans 20-35% of embryogenesis in most species, which makes it difficult to define the mechanisms that transduce temperature into a signal for ovarian versus testicular development. We present an extensive set of studies that define a brief period when high temperature specifies, and then determines, ovarian fate in a northern population of Snapping Turtles, Chelydra serpentina. We shifted embryos from male to female temperatures, or vice versa, at various stages of development. Gonads in embryos incubated at female temperatures commit to ovarian fate earlier (by stage 18) than gonads in embryos incubated at male temperatures commit to testicular fate (by stages 19-21). In double shift studies, embryos were incubated at a female temperature, exposed to a male temperature for set times, and shifted back to the original temperature, or vice versa. The time required to induce ovarian development (≤6 days at female temperatures) was much shorter than the time required to induce testicular formation (>20 days at male temperatures). Differentiation of the gonads at the histological level occurred after the sex-determining period. Nevertheless, we found that a change in temperature rapidly (within 24h) influenced expression and splicing of WT1 mRNA: the absolute abundance of WT1 mRNA, the relative abundance of +KTS versus -KTS isoforms, as well as the ratio of +KTS:-KTS isoforms was higher in gonads at a male versus a female temperature. In conclusion, ovarian fate is more readily determined than testicular fate in Snapping Turtle embryos. The short sex-determining period in this species (6-8% of embryogenesis) will facilitate studies of molecular mechanisms for specification and determination of gonad fate by temperature.
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Adjustments in cholinergic, adrenergic and purinergic control of cardiovascular function in Snapping Turtle embryos (Chelydra serpentina) incubated in chronic hypoxia
Journal of Comparative Physiology B, 2014Co-Authors: John Eme, Turk Rhen, Dane A. CrossleyAbstract:Adenosine is an endogenous nucleoside that acts via G-protein coupled receptors. In vertebrates, arterial or venous adenosine injection causes a rapid and large bradycardia through atrioventricular node block, a response mediated by adenosine receptors that inhibit adenylate cyclase and decrease cyclic AMP concentration. Chronic developmental hypoxia has been shown to alter cardioregulatory mechanisms in reptile embryos, but adenosine’s role in mediating these responses is not known. We incubated Snapping Turtle embryos under chronic normoxic (N21; 21 % O_2) or chronic hypoxic conditions (H10; 10 % O_2) beginning at 20 % of embryonic incubation. H10 embryos at 90 % of incubation were hypotensive relative to N21 embryos in both normoxic and hypoxic conditions. Hypoxia caused a hypotensive bradycardia in both N21 and H10 embryos during the initial 30 min of exposure; however, f _H and P _m both trended towards increasing during the subsequent 30 min, and H10 embryos were tachycardic relative to N21 embryos in hypoxia. Following serial ≥1 h exposure to normoxic and hypoxic conditions, a single injection of adenosine (1 mg kg^−1) was given. N21 and H10 embryos responded to adenosine injection with a rapid and large hypotensive bradycardia in both normoxia and hypoxia. Gene expression for adenosine receptors were quantified in cardiac tissue, and Adora1 mRNA was the predominant receptor subtype with transcript levels 30–82-fold higher than Adora2A or Adora2B. At 70 % of incubation, H10 embryos had lower Adora1 and Adora2B expression compared to N21 embryos. Expression of Adora1 and Adora2B decreased in N21 embryos during development and did not differ from H10 embryos at 90 % of incubation. Similar to previous results in normoxia, H10 embryos in hypoxia were chronically tachycardic compared to N21 embryos before and after complete cholinergic and adrenergic blockade. Chronic hypoxia altered the development of normal cholinergic and adrenergic tone, as well as adenosine receptor mRNA levels. This study demonstrates that adenosine may be a major regulator of heart rate in developing Snapping Turtle embryos, and that chronic hypoxic incubation alters the response to hypoxic exposure.
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the platelet derived growth factor signaling system in Snapping Turtle embryos chelydra serpentina potential role in temperature dependent sex determination and testis development
General and Comparative Endocrinology, 2009Co-Authors: Turk Rhen, Anthony L Schroeder, Adam Jangula, Rikki WoodwardboshAbstract:The platelet-derived growth factor (Pdgf) signaling system is known to play a significant role during embryonic and postnatal development of testes in mammals and birds. In contrast, genes that comprise the Pdgf system in reptiles have never been cloned or studied in any tissue, let alone developing gonads. To explore the potential role of PDGF ligands and their receptors during embryogenesis, we cloned cDNA fragments of Pdgf-A, Pdgf-B, and receptors PdgfR-α and PdgfR-β in the Snapping Turtle, a reptile with temperature-dependent sex determination (TSD). We then compared gene expression profiles in gonads from embryos incubated at a male-producing temperature to those from embryos at a female-producing temperature, as well as between hatchling testes and ovaries. Expression of Pdgf-B mRNA in embryonic gonads was significantly higher at a male temperature than at a female temperature, but there was no difference between hatchling testes and ovaries. This developmental pattern was reversed for Pdgf-A and PdgfR-α mRNA: expression of these genes did not differ in embryos, but diverged in hatchling testes and ovaries. Levels of PdgfR-β mRNA in embryonic gonads were not affected by temperature and did not differ between testes and ovaries. However, expression of both receptors increased at least an order of magnitude from the embryonic to the post-hatching period. Finally, we characterized expression of these genes in several other embryonic tissues. The brain, heart, and liver displayed unique expression patterns that distinguished these tissues from each other and from intestine, lung, and muscle. Incubation temperature had a significant effect on expression of PdgfR-α and PdgfR-β in the heart but not other tissues. Together, these findings demonstrate that temperature has tissue specific effects on the Pdgf system and suggest that Pdgf signaling is involved in sex determination and the ensuing differentiation of testes in the Snapping Turtle.
