Publications

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non-destructive techniques for biomonitoring of spatial, temporal, and demographic patterns of mercury bioaccumulation and maternal transfer in turtles.mercury (hg) is a globally ubiquitous pollutant that has received much attention due to its toxicity to humans and wildlife. the development of non-destructive sampling techniques is a critical step for sustainable monitoring of hg accumulation. we evaluated the efficacy of non-destructive sampling techniques and assessed spatial, temporal, and demographic factors that influence hg bioaccumulation in turtles. we collected muscle, blood, nail, and eggs from snapping turtles (chelydra serpentina) ...201323500054
physiological responses to freezing in hatchlings of freeze-tolerant and -intolerant turtles.freeze tolerance is a complex cold-hardiness adaptation that has independently evolved in a diverse group of organisms, including several ectothermic vertebrates. because little is known about the mechanistic basis for freeze tolerance in reptiles, we compared responses to experimental freezing in winter-acclimatized hatchlings representing nine taxa of temperate north american turtles, including ones that tolerated freezing and others that did not. viability rates of hatchlings frozen to -3 deg ...200616758216
an immunohistochemical approach to identify the sex of young marine turtles.marine turtles exhibit temperature-dependent sex determination (tsd). during critical periods of embryonic development, the nest's thermal environment directs whether an embryo will develop as a male or female. at warmer sand temperatures, nests tend to produce female-biased sex ratios. the rapid increase of global temperature highlights the need for a clear assessment of its effects on sea turtle sex ratios. however, estimating hatchling sex ratios at rookeries remains imprecise due to the lack ...201728296279
critical windows of cardiovascular susceptibility to developmental hypoxia in common snapping turtle (chelydra serpentina) embryos.environmental 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 ...201525730266
sizing bands on autoradiograms: a study of precision for scoring dna fingerprints.we replicated dna fingerprints of snapping turtles (chelydra serpentina) and hypervariable restriction fragments of red-winged blackbirds (agelaius phoeniceus) to estimate the between-blot and between-lane components of variance in molecular weights of restriction fragments. molecular weight standards were included in every lane, and bands were sized using a sonic digitizer. in both studies, a strong positive correlation was found between band size and coefficient of variation (cv; mean = 0.7%). ...20061674911
mercury exposure is associated with negative effects on turtle reproduction.mercury (hg), a ubiquitous and highly toxic bioaccumulative contaminant, can maternally transfer and elicit deleterious effects on adult reproduction and offspring phenotype in fish, amphibians, and birds. however, the effects of hg on reproduction remain largely unstudied in reptiles. we evaluated the consequences of maternally transferred hg on a long-lived aquatic omnivore, the common snapping turtle (chelydra serpentina). we collected eggs and tissues from gravid female turtles along a broad ...201323360167
experimental exposure of eggs to polybrominated diphenyl ethers bde-47 and bde-99 in red-eared sliders (trachemys scripta elegans) and snapping turtles (chelydra serpentina) and possible species-specific differences in debromination.polybrominated diphenyl ethers (pbdes) are a bioaccumulative, persistent, and toxic class of flame retardants that can potentially impact turtles in natural habitats via exposure through maternal transfer. to simulate maternal transfer in the present study, pbde congeners bde-47 and bde-99 were topically applied to the eggshell and were allowed to diffuse into the egg contents of the red-eared slider (trachemys scripta elegans) and snapping turtle (chelydra serpentina). eggs were topically dosed ...201323147837
oviductal morphology in relation to hormonal levels in the snapping turtle, chelydra serpentina.microscopic and in situ visual observations were used to relate circulating hormone levels to morphological changes in the oviduct of the snapping turtle chelydra serpentina throughout the ovarian cycle. increase in levels of progesterone (p), estradiol (e2) and testosterone (t) levels coincide with an increase in number and growth of endometrial glands, luminal epithelial cells and secretory droplets throughout the oviduct. testosterone and estradiol levels rose significantly (p < 0.05) after t ...200616384588
temperature-dependent sex determination modulates cardiovascular maturation in embryonic snapping turtles chelydra serpentina.we investigated sex differences in cardiovascular maturation in embryos of the snapping turtle chelydra serpentina, a species with temperature-dependent sex determination. one group of eggs was incubated at 26.5°c to produce males. another group of eggs was incubated at 26.5°c until embryos reached stage 17; eggs were then shifted to 31°c for 6 days to produce females, and returned to 26.5°c for the rest of embryogenesis. thus, males and females were at the same temperature when autonomic tone w ...201323125337
polycyclic aromatic hydrocarbons affect survival and development of common snapping turtle (chelydra serpentina) embryos and hatchlings.polycyclic aromatic hydrocarbons (pahs) are toxic compounds found in the john heinz national wildlife refuge in philadelphia, pennsylvania. we assessed the impact of pahs and crude oil on snapping turtle development and behavior by exposing snapping turtle eggs from the refuge and from three clean reference sites to individual pahs or a crude oil mixture at stage 9 of embryonic development. exposure to pahs had a significant effect on survival rates in embryos from one clean reference site, but ...200616360251
anoxia tolerance and freeze tolerance in hatchling turtles.freezing survival in hatchling turtles may be limited by ischemic anoxia in frozen tissues and the associated accumulation of lactate and reactive oxygen species (ros). to determine whether mechanisms for coping with anoxia are also important in freeze tolerance, we examined the association between capacities for freezing survival and anoxia tolerance in hatchlings of seven species of turtles. tolerance to freezing (-2.5 degrees c) was high in emydoidea blandingii, chrysemys picta, terrapene orn ...200515739066
nondestructive indices of mercury exposure in three species of turtles occupying different trophic niches downstream from a former chloralkali facility.turtles are useful for studying bioaccumulative pollutants such as mercury (hg) because they have long life spans and feed at trophic levels that result in high exposure to anthropogenic chemicals. we compared total hg concentrations in blood and toenails of three species of turtles (chelydra serpentina, sternotherus odoratus, and graptemys geographica) with different feeding ecologies from locations up- and downstream of a superfund site in virginia, usa. mercury concentrations in turtle tissue ...201323010870
observations on the leech placobdella ornata feeding from bony tissues of turtles.the leech placobdella ornata was observed feeding from the blood sinuses of the plastron and carapace bones of chelydra serpentina and chrysemys picta. evidence of successful feeding included blood upwelling from the point of attachment and gastric ceca of the leeches freshly filled with blood after removal. there was an apparent preference for the sulci between scales of the shell.200415562628
skeletal development of macrochelys temminckii (reptilia: testudines: chelydridae).few descriptions of the development and sequence of chondrification and ossification of the entire skeleton of turtles exist, particularly compared to other groups of reptiles. in this study, the embryonic skeleton and its ontogenesis are described for the alligator snapping turtle, macrochelys temminckii (chelydridae). morphological descriptions utilize cleared and double-stained embryonic specimens and form the basis of comparison of the ontogenesis of the skeleton between this species and its ...200515536645
diagnosis of skeletal injuries in chelonians using computed tomography.computed tomography (ct) was used to diagnose the cause of lameness in a radiated tortoise (geochelone radiata) and to determine the extent of shell and skeletal trauma in two snapping turtles (chelydra serpentina). the radiated tortoise's lameness was ultimately attributed to luxation of the right-shoulder joint that was not detected during plain film radiography. axial and appendicular fractures were identified in one of the snapping turtles that were not detected during plain film radiography ...200415305520
comparative effects of in ovo exposure to sodium perchlorate on development, growth, metabolism, and thyroid function in the common snapping turtle (chelydra serpentina) and red-eared slider (trachemys scripta elegans).perchlorate is a surface and groundwater contaminant found in areas associated with munitions and rocket manufacturing and use. it is a thyroid-inhibiting compound, preventing uptake of iodide by the thyroid gland, ultimately reducing thyroid hormone production. as thyroid hormones influence metabolism, growth, and development, perchlorate exposure during the embryonic period may impact embryonic traits that ultimately influence hatchling performance. we topically exposed eggs of red-eared slide ...201222871607
lactate accumulation, glycogen depletion, and shell composition of hatchling turtles during simulated aquatic hibernation.we submerged hatchling western painted turtles chrysemys picta schneider, snapping turtles chelydra serpentina l. and map turtles graptemys geographica le sueur in normoxic and anoxic water at 3 degrees c. periodically, turtles were removed and whole-body [lactate] and [glycogen] were measured along with relative shell mass, shell water, and shell ash. we analyzed the shell for [na+], [k+], total calcium, total magnesium, pi and total co2. all three species were able to tolerate long-term submer ...200415235017
cutaneous fibroma in a captive common snapping turtle (chelydra serpentina).an adult female common snapping turtle (chelydra serpentina) had a mass on the plantar surface of the right forelimb that was removed surgically. microscopical examination revealed many spindle cells with mild anisocytosis and anisokaryosis and a surrounding collagenous stroma. there were no mitoses. immunohistochemistry showed that the spindle cells expressed vimentin, but not desmin. a diagnosis of cutaneous fibroma was made. tumours are reported uncommonly in chelonian species. cutaneous fibr ...201222578330
lymphoid aggregates in gonads of embryos, hatchlings, and young of turtles with temperature-dependent sex determination.cellular infiltrations forming lymphoid-like aggregates were previously observed in gonads of two turtle species exhibiting temperature-dependent sex determination (tsd): at hatching in chelydra serpentina; at and after hatching in emys orbicularis. we show here that such aggregates are also present in gonads of testudo graeca by the end of embryonic development, suggesting that their occurrence is general in turtles. since in c. serpentina, infiltrations were observed mainly in testes exhibitin ...200414743515
widespread reproductive variation in north american turtles: temperature, egg size and optimality.theory predicts the existence of an optimal offspring size that balances the trade-off between offspring fitness and offspring number. however, in wild populations of many species, egg size can still vary from year to year for unknown reasons. here, we hypothesize that among-year variation in population mean egg size of freshwater turtles is partly a consequence of their gonadal sensitivity to seasonal temperatures, a physiological mechanism which principally functions to synchronize reproductio ...201222541670
the physiology of overwintering in a turtle that occupies multiple habitats, the common snapping turtle (chelydra serpentina).common snapping turtles, chelydra serpentina (linnaeus), were submerged in anoxic and normoxic water at 3 degrees c. periodic blood samples were taken, and po(2), pco(2), ph, [na(+)], [k(+)], [cl(-)], total ca, total mg, [lactate], [glucose], hematocrit, and osmolality were measured; weight gain was determined; and plasma [hco(3)(-)] was calculated. submergence in normoxic water caused a decrease in pco(2) from 10.8 to 6.9 mmhg after 125 d, partially compensating a slight increase in lactate and ...201612529844
highly elevated levels of perfluorooctane sulfonate and other perfluorinated acids found in biota and surface water downstream of an international airport, hamilton, ontario, canada.per- and poly-fluorinated compounds (pfcs), which include perfluorinated carboxylates (pfcas) and sulfonates (pfsas) and various precursors, are used in a wide variety of industrial, commercial and domestic products. this includes aqueous film forming foam (afff), which is used by military and commercial airports as fire suppressants. in a preliminary assessment prior to this study, very high concentrations (>1 ppm wet weight) of the pfsa, perfluorooctane sulfonate (pfos), were discovered in the ...201222208739
wetness of the nest environment influences cardiac development in pre- and post-natal snapping turtles (chelydra serpentina).we dissected hearts from near-term embryos and hatchlings of common snapping turtles (chelydridae: chelydra serpentina) whose eggs had incubated on wet or dry substrates, and then dried and individually weighed the heart and yolk-free carcass from each animal. hearts and carcasses of prenatal and neonatal animals grew at different rates, and the patterns of growth by both heart and carcass differed between wet and dry environments. hearts grew faster, both in actual mass and in mass adjusted for ...200212095870
absorption of current use pesticides by snapping turtle (chelydra serpentina) eggs in treated soil.reptiles often breed within agricultural and urban environments that receive frequent pesticide use. consequently, their eggs and thus developing embryos may be exposed to pesticides. our objectives were to determine (i) if turtle eggs are capable of absorbing pesticides from treated soil, and (ii) if pesticide absorption rates can be predicted by their chemical and physical properties. snapping turtle (chelydra serpentina) eggs were incubated in soil that was treated with 10 pesticides (atrazin ...201121862099
the pulmonary surfactant system matures upon pipping in the freshwater turtle chelydra serpentina.pulmonary surfactant (ps), a mixture of phospholipids (pl), neutral lipids and surfactant proteins (sp), lowers surface tension within the lung, which increases lung compliance and improves the removal of fluid at birth. here, we have examined the expression of thyroid transcription factor-1 (ttf-1) and the surfactant protein sp-b, and also the composition of pulmonary surfactant lipids in the developing lung of the turtle chelydra serpentina. lavage and lung tissue were collected from late embr ...200211854378
toxicity of pesticide and fertilizer mixtures simulating corn production to eggs of snapping turtles (chelydra serpentina).many reptiles oviposit in soils associated with agricultural landscapes. we evaluated the toxicity of a pesticide and fertilizer regime similar to those used in corn production in ontario on the survivorship of exposed snapping turtle (chelydra serpentina) eggs. the herbicides atrazine, dimethenamid, and glyphosate, the pyrethroid insecticide tefluthrin, and the fertilizer ammonia, were applied to clean soil, both as partial mixtures within chemical classes, as well as complete mixtures. eggs we ...201121831407
transmission of haemogregarina balli from painted turtles to snapping turtles through the leech placobdella ornata.six leeches (placobdella ornata) were allowed to feed on a painted turtle (chrysemys picta marginata) infected with haemogregarina balli and subjected to a period of diapause before being allowed to feed on 2 laboratory-reared snapping turtles (chelydra serpentina). weekly examination of thin blood films revealed infections of the turtles at 130 days postfeeding. these observations provide support for broad host specificity of hemogregarine parasites of chelonians.200111695407
multi-scale hierarchy of chelydra serpentina: microstructure and mechanical properties of turtle shell.carapace, the protective shell of a freshwater snapping turtle, chelydra serpentina, shields them from ferocious attacks of their predators while maintaining light-weight and agility for a swim. the microstructure and mechanical properties of the turtle shell are very appealing to materials scientists and engineers for bio-mimicking, to obtain a multi-functional surface. in this study, we have elucidated the complex microstructure of a dry chelydra serpentina's shell which is very similar to a m ...201121783154
organochlorine pesticides, pcbs, dibenzodioxin, and furan concentrations in common snapping turtle eggs (chelydra serpentina serpentina) in akwesasne, mohawk territory, ontario, canada.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 ...200111443374
mercury concentrations in snapping turtles (chelydra serpentina) correlate with environmental and landscape characteristics.mercury (hg) deposited onto the landscape can be transformed into methylmercury (mehg), a neurotoxin that bioaccumulates up the aquatic food chain. here, we report on hg concentrations in snapping turtles (chelydra serpentina) across new york state, usa. the objectives of this study were to: (1) test which landscape, water, and biometric characteristics correlate with total hg (thg) concentrations in snapping turtles; and (2) determine whether soft tissue thg concentrations correlate with scute ...201121688194
morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution.the turtle shell is an evolutionary novelty that is synapomorphic for chelonians. the carapace is initiated by the entrapment of the ribs by the carapacial ridge (cr), a lateral bulge of the dorsal ectoderm and dermal mesoderm. the mechanisms by which the cr is initiated, the ribs entrapped and the dorsal dermis ossified, remains unknown. similarly, the formation of the plastron remains unexplained. here, we present a series of anatomical investigations into plastron and carapace formation in th ...200711341674
an egg injection technique to evaluate the effect of polychlorinated biphenyls on the hatching success of the snapping turtle (chelydra serpentina serpentina).embryos of oviparous organisms are exposed to contaminants by two pathways: contaminant uptake from the surrounding environment, and the transfer from female to offspring (maternal transfer). the initial source of contaminant exposure for most embryos is likely to be maternal transfer; therefore, maternal transfer studies are critical in determining the effects of contaminants on future populations. injection of contaminants directly into eggs is one route of experimental contaminant exposure th ...201121191884
lipid metabolism during embryonic development of the common snapping turtle, chelydra serpentina.the metabolism of lipids and fatty acids during embryonic development of chelydra serpentina (common snapping turtle) was investigated. substantial changes in lipid class and fatty acid composition occurred as lipids were transferred from the yolk to the yolk sac membrane (ysm) and then to the brain, eyes, heart, and lungs of the hatchling. lipids were hydrolyzed in the yolk prior to transport to the ysm, shown by a large increase in free fatty acids (ffas) during the second half of development. ...200919416694
respiratory responses to short term hypoxia in the snapping turtle, chelydra serpentina.among vertebrates, turtles are able to tolerate exceptionally low oxygen tensions. we have investigated the compensatory mechanisms that regulate respiration and blood oxygen transport in snapping turtles during short exposure to hypoxia. snapping turtles started to hyperventilate when oxygen levels dropped below 10% o(2). total ventilation increased 1.75-fold, essentially related to an increase in respiration frequency. during normoxia, respiration occurred in bouts of four to five breaths, whe ...200010936762
cross-reactivity of a polyclonal antibody against chinemys reevesii vitellogenin with the vitellogenins of other turtle species: chelydra serpentina , macrochelys temminckii , and pelodiscus sinensis.vitellogenin (vtg), a yolk-precursor protein in oviparous vertebrates, is a useful biomarker for reproductive physiology and environmental estrogenic pollution. to examine interspecific applicability of an enzyme-linked immunosorbent assay (elisa) for quantifying chinemys reevesii vtg, we observed cross-reactivity between a polyclonal antibody against chinemys reevesii vtg and the vtgs from other turtle species: chelydra serpentina (chelydridae), macrochelys temminckii (chelydridae), and pelodis ...200819267600
an ontogenetic shift in the response of heart rates to temperature in the developing snapping turtle (chelydra serpentina).the affect of acute changes in temperature on heart rates was investigated for the first time in a developing reptile. heart rates were determined early and late in incubation in snapping turtle (chelydra serpentina) eggs. late in incubation heart rates at any given temperature were lower than those observed early in incubation. the results of temperature switching experiments late in incubation were consistent with thermal acclimation.200010745125
accumulation and maternal transfer of polychlorinated biphenyls in snapping turtles of the upper hudson river, new york, usa.we conducted field studies over three years to assess body burdens and maternal transfer of polychlorinated biphenyls (pcbs) as well as indices of sexual dimorphism in snapping turtles (chelydra serpentina) of the upper hudson river (ny, usa.) we collected adult turtles in areas known to be contaminated with pcbs and in nearby reference areas for measurement of body size, precloacal length, and penis size. we analyzed pcb concentrations in eggs collected over three years and in whole blood from ...200818699700
influence of water availability during incubation on hatchling size, body composition, desiccation tolerance, and terrestrial locomotor performance in the snapping turtle chelydra serpentina.the effects of water availability during incubation on the water contents of neonatal snapping turtles at hatching were examined, along with the influence of hatchling water content on desiccation tolerance and terrestrial locomotor performance. the water contents of hatchlings from eggs incubated on wet substrates were both absolutely and proportionally greater than were those of hatchlings from eggs incubated on dry substrates. hatchlings with greater water contents at hatching were able to su ...200610603335
carbon dioxide (co2) laser treatment of cutaneous papillomas in a common snapping turtle, chelydra serpentina.carbon dioxide (co2) laser was used to treat multiple cutaneous papillomas on an adult female common snapping turtle, chelydra serpentina serpentina. a combination of excisional and ablative techniques provided excellent intraoperative visibility and postoperative results due to the laser's unique ability to incise and vaporize soft tissue.200818634218
expression of putative sex-determining genes during the thermosensitive period of gonad development in the snapping turtle, chelydra serpentina.modes of sex determination are quite variable in vertebrates. the developmental decision to form a testis or an ovary can be influenced by one gene, several genes, environmental variables, or a combination of these factors. nevertheless, certain morphogenetic aspects of sex determination appear to be conserved in amniotes. here we clone fragments of nine candidate sex-determining genes from the snapping turtle chelydra serpentina, a species with temperature-dependent sex determination (tsd). we ...200718391536
effect of dichlorodiphenyltrichloroethane on sex determination of the common snapping turtle (chelydra serpentina serpentina).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 ...199910381306
snapping turtles (chelydra serpentina) as bioindicators in canadian areas of concern in the great lakes basin. 1. polybrominated diphenyl ethers, polychlorinated biphenyls, and organochlorine pesticides in eggs.we examined the concentrations and spatial patterns of congeners of pbdes, pcbs, and organochlorine pesticides in snapping turtle (chelydra serpentina) eggs from areas of concern (aocs) on the canadian shores of lake ontario, st. lawrence river, and connecting channels. eggs from lyons creek (niagara river aoc) reflected a local pcb source over a range of 7.5 km (3.2-10.8) from the welland canal. pcb contamination in eggs declined with increasing distance from the welland canal, whereas the rela ...200718044496
photoreceptor coupling in turtle retina.photoreceptors in the isolated turtle retina of two species of turtle, chelydra serpentina and pseudemus scripta elegans, were penetrated with double-barrel electrodes. physiological responses were recorded through one barrel and neurobiotin tracer was injected from the other. intracellular injection of neurobiotin revealed patterns of tracer-coupled photoreceptors. both the patterns of tracer coupling and the electrophysiology suggest a high degree of specificity of connections. rods seem to be ...20159682876
snapping turtles (chelydra serpentina) as bioindicators in canadian areas of concern in the great lakes basin. ii. changes in hatching success and hatchling deformities in relation to persistent organic pollutants.hatching success and deformities in snapping turtle hatchlings (chelydra serpentina) were evaluated using eggs collected from 14 sites in the canadian lower great lakes, including areas of concern (aoc), between 2001 and 2004. eggs were analyzed for pcbs, pbdes, and pesticides. between 2002 and 2004, hatchling deformity rates were highest in two aocs (18.3-28.3%) compared to the reference sites (5.3-11.3%). hatching success was poorest in three aocs (71.3-73.1%) compared to the reference sites ( ...200818039552
embryonic temperature influences juvenile temperature choice and growth rate in snapping turtles chelydra serpentina.snapping turtles (chelydra serpentina) demonstrate temperature-dependent sex determination (tsd): intermediate egg incubation temperatures (23-27 degrees c) produce males, while extreme temperatures produce females. snapping turtles are also sexually dimorphic: adult males are typically larger than females. previous researchers hypothesized that male-producing egg temperatures enhanced the growth rate of juvenile turtles, resulting in the adult dimorphism and potentially providing an adaptive be ...19989503646
toxicity of nitrogenous fertilizers to eggs of snapping turtles (chelydra serpentina) in field and laboratory exposures.many reptiles oviposit in soil of agricultural landscapes. we evaluated the toxicity of two commonly used nitrogenous fertilizers, urea and ammonium nitrate, on the survivorship of exposed snapping turtle (chelydra serpentina) eggs. eggs were incubated in a community garden plot in which urea was applied to the soil at realistic rates of up to 200 kg/ha in 2004, and ammonium nitrate was applied at rates of up to 2,000 kg/ha in 2005. otherwise, the eggs were unmanipulated and were subject to ambi ...200717702542
embryonic temperature influences juvenile temperature choice and growth rate in snapping turtles chelydra serpentina.snapping turtles (chelydra serpentina) demonstrate temperature-dependent sex determination (tsd): intermediate egg incubation temperatures (23-27 degreesc) produce males, while extreme temperatures produce females. snapping turtles are also sexually dimorphic: adult males are typically larger than females. previous researchers hypothesized that male-producing egg temperatures enhanced the growth rate of juvenile turtles, resulting in the adult dimorphism and potentially providing an adaptive ben ...19989427676
influence of feeding ecology on blood mercury concentrations in four species of turtles.mercury is a relatively well-studied pollutant because of its global distribution, toxicity, and ability to bioaccumulate and biomagnify in food webs: however, little is known about bioaccumulation and toxicity of hg in turtles. total hg (thg) concentrations in blood were determined for 552 turtles representing four different species (chelydra serpentina, sternotherus odoratus, chrysemys picta, and pseudemys rubriventris) from a hg-contaminated site on the south river (va, usa) and upstream refe ...200717702349
can natural phenotypic variances be estimated reliably under homogeneous laboratory conditions?the phenotypic variance is assumed to be greater in a more heterogeneous environment. the validity of this assumption is important for microevolutionists to extrapolate results from the laboratory to field environments. we subjected clutches of eggs from common snapping turtles (chelydra serpentina) to a split-family design to evaluate the variability in incubation time and four size traits of neonates from eggs incubated in the laboratory and those left in situ. mean size measurements were simi ...200717584235
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.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 lyn ...19968975824
comparative shell buffering properties correlate with anoxia tolerance in freshwater turtles.freshwater turtles as a group are more resistant to anoxia than other vertebrates, but some species, such as painted turtles, for reasons not fully understood, can remain anoxic at winter temperatures far longer than others. because buffering of lactic acid by the shell of the painted turtle is crucial to its long-term anoxic survival, we have tested the hypothesis that previously described differences in anoxia tolerance of five species of north american freshwater turtles may be explained at l ...200717008457
polychlorinated biphenyl concentrations, congener profiles, and ratios in the fat tissue, eggs, and plasma of snapping turtles (chelydra s. serpentina) from the ohio basin of lake erie, usa.concentrations and profiles of polychlorinated biphenyls (pcbs) were determined in three tissues of adult snapping turtles (chelydra serpentina serpentina) from six locations in the ohio basin of lake erie to characterize tissue variation and geographic trends. the locations included the ohio areas of concern, i.e., the ashtabula, black, and maumee rivers; the ottawa river near toledo; and two reference sites. mean total pcbs were greatest in turtles from the ottawa river followed by the maumee, ...200616583258
environmentally induced variation in body size of turtles hatching in natural nests.eggs from three snapping turtles (chelydra serpentina) were divided between two natural nests in a factorial experiment assessing the role of the nest environment as a cause for variation in body size and energy reserves of hatchlings at our study site in northcentral nebraska. nest # 1 was located in an unshaded area on the south side of a high sandhill, whereas nest #2 was located in an unshaded area on level ground. eggs in nest #1 increased in mass over the course of incubation, with eggs at ...199328313447
effects of environmentally relevant concentrations of atrazine on gonadal development of snapping turtles (chelydra serpentina).the herbicide atrazine has been suspected of affecting sexual development by inducing aromatase, resulting in the increased conversion of androgens to estrogens. we used snapping turtles (chelydra serpentina), a species in which sex is dependent on the production of estrogen through aromatase activity in a temperature-dependent manner, to investigate if environmentally relevant exposures to atrazine affected gonadal development. eggs were incubated in soil to which atrazine was applied at a typi ...200616519315
high incidence of deformity in aquatic turtles in the john heinz national wildlife refuge.the john heinz national wildlife refuge is subject to pollution from multiple sources. we studied development of snapping turtle (chelydra serpentina) and painted turtle (chrysemys picta) embryos from the refuge from 2000 through 2003. mean annual deformity rate of pooled painted turtle clutches over four years ranged from 45 to 71%, while that of snapping turtle clutches ranged from 13 to 19%. lethal deformities were more common than minor or moderate deformities in embryos of both species. adu ...200616360253
heritable variation for sex ratio under environmental sex determination in the common snapping turtle (chelydra serpentina).the magnitude of quantitative genetic variation for primary sex ratio was measured in families extracted from a natural population of the common snapping turtle (chelydra serpentina), which possesses temperature-dependent sex determination (tsd). eggs were incubated at three temperatures that produced mixed sex ratios. this experimental design provided estimates of the heritability of sex ratio in multiple environments and a test of the hypothesis that genotype x environment (g x e) interactions ...19921592234
secretory proteins in the reproductive tract of the snapping turtle, chelhydra serpentina.sds-polyacrylamide gel electrophoresis was used to separate the secretory proteins produced by the epithelial and endometrial glands of the uterine tube and uterus in the snapping turtle chelydra serpentina. the proteins were analyzed throughout the phases of the reproductive cycle from may to august, including preovulatory, ovulatory, postovulatory or luteal, and vitellogenic phases. the pattern of secretory proteins is quite uniform along the length of the uterine tube, and the same is true of ...200415596394
characterization of contaminants in snapping turtles (chelydra serpentina) from canadian lake erie areas of concern: st. clair river, detroit river, and wheatley harbour.pcbs, organochlorine pesticides and dioxins/furans in snapping turtle eggs and plasma (chelydra serpentina) were evaluated at three areas of concern (aocs) on lake erie and its connecting channels (st. clair river, detroit river, and wheatley harbour), as well as two inland reference sites (algonquin provincial park and tiny marsh) in 2001-2002. eggs from the detroit river and wheatley harbour aocs had the highest levels of p,p'-dde (24.4 and 57.9 ng/g) and sum pcbs (928.6 and 491.0 ng/g) wet we ...200415276278
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).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) a ...199815093107
survival and behavior of freshwater turtles after rehabilitation from an oil spill.an oil spill in february 2000 at the john heinz national wildlife refuge in southeastern pennsylvania affected four species of freshwater turtles including painted turtles (chrysemys picta), snapping turtles (chelydra serpentina), red-eared slider turtles (trachemys scripta), and red-bellied turtles (pseudemys rubriventris). in the summer and fall of 2000, there were no differences in survival, home range, and temperature preference of 16 oil exposed/rehabilitated (oer) turtles, 18 possibly expo ...200312927492
the role of arginine vasotocin and prostaglandin f2 alpha on oviposition and luteolysis in the common snapping turtle chelydra serpentina.the administration of arginine vasotocin (avt) to gravid snapping turtles with steroidogenically active corpora lutea and high plasma progesterone concentration (1480 +/- 155 pg/ml) did not trigger oviposition, whereas 12 days after ovulation when luteolysis occurred and plasma progesterone concentration was low (570 +/- 78 pg/ml), treatment with avt caused oviposition. controls with high plasma progesterone concentration (1605 +/- 185 pg/ml) oviposited 15-23 days after ovulation when plasma pro ...19883162890
yolk hormone levels in the eggs of snapping turtles and painted turtles.although yolk steroids appear to play important roles in the development, growth, and behavior of some birds, their effects in oviparous reptiles are largely unknown. these investigations were initiated to determine initial levels of steroid hormones in the yolks of eggs from two turtle species. clutches of snapping turtle (chelydra serpentina) and of painted turtle (chrysemys picta) eggs were collected and individual egg yolks were analyzed for estradiol-17beta (e(2)) and testosterone (t) using ...200212161198
electron microscopy of golgi-impregnated photoreceptors reveals connections between red and green cones in the turtle retina.red and green cones of two turtle species (pseudemys scripta elegans and chelydra serpentina) retina have been stained with golgi procedures and examined by light microscopy of whole-mount tissue and by electron microscopy of serial thin sections. by light microscopy, red and green single cones appear indistinguishable, but double cones can be readily identified. all golgi-stained photoreceptors in turtle retina have a spray of telodendria radiating from their synaptic pedicles. the telodendria ...19854031990
sexually dimorphic morphology of hatchling snapping turtles (chelydra serpentina) from contaminated and reference sites in the great lakes and st. lawrence river basin, north america.some organochlorine pesticides and industrial chemicals may alter sexually dimorphic traits through endocrine disruption. therefore, we examined a sexually dimorphic trait, precloacal length, of hatchling snapping turtles (chelydra serpentina) incubated from 31 clutches from a heavily contaminated site (hamilton harbour, on, canada; n = 14), a moderately contaminated site (akwesasne mohawk territory; n = 3), and from a reference site (algonquin provincial park, on, canada; n = 14). the mean sum ...200212013138
development of the ovarian follicles in relation to changes in plasma parameters and 5 delta 3 beta hsd in snapping turtle, chelydra serpentina.follicular development in snapping turtle, chelydra serpentina, was studied in relation to changes in plasma levels of estradiol-17 beta, total protein, calcium, inorganic phosphate and cholesterol. histochemical reaction for 3 beta-hsd in granulosa and theca cells of the follicles is strong during the preovulatory and vitellogenic phases when the follicles attain their maximum size (18-22 mm) and estradiol is at a high level. the reaction for 3 beta-hsd is weal during the postovulatory phase wh ...19852864192
expression of p450(arom) in malaclemys terrapin and chelydra serpentina: a tale of two sites.the formation of estrogens from androgens in all vertebrates is catalyzed by the "aromatase" complex, which consists of a membrane bound p(450) enzyme, p(450) aromatase (which binds the androgen substrate and inserts an oxygen into the molecule), and a flavoprotein (nadph-cytochrome p450 reductase). among vertebrates, the two major sites of aromatase expression are the brain and gonads. given the importance of estrogen in reptile sex determination, we set out to examine whether p450arom was invo ...200111748616
resistance of the shell membrane and mineral layer to diffusion of oxygen and water in flexible-shelled eggs of the snapping turtle (chelydra serpentina).at oviposition, flexible eggshells of many turtles have an outer mineral layer and an inner membrane layer of approximately equal thickness. we measured conductances of both layers to h2o and o2 at various levels of eggshell hydration. both the mineral layer of the eggshell and the shell membrane offer significant resistance to diffusion of water vapor and oxygen in eggshells of the snapping turtle, chelydra serpentina. conductance to water vapor increases in both the membrane and mineral layer ...19826890707
possible adaptive value of water exchanges in flexible-shelled eggs of turtles.use of energy reserves by embryos of common snapping turtles (chelydra serpentina) is related to the hydric conditions to which eggs are exposed during incubation and to the net exchanges of water through the eggshells. embryos developing inside eggs with a relatively favorable water balance use more of their energy reserves metabolically and grow larger before hatching than embryos inside eggs with less favorable water exchanges.198117760193
snapping turtles (chelydra serpentina) as monitors for mercury contamination of aquatic environments.we assessed the distribution of mercury in snapping turtles (chelydra serpentina) by analyzing front shoulder muscle, back leg muscle, tail muscle, blood, liver, and marginal carapacial scute (shell) of 26 adult turtles from five small lakes. total mercury concentration in muscle ranged from 50 to 500 ng g(-1) wet weight and was highly correlated among the three tissue locations. there was no relationship between muscle mercury concentration and body size. mercury concentration in blood was simi ...200111683228
cold-hardiness and evaporative water loss in hatchling turtles.north american turtles hatch in late summer and spend their first winter either on land or underwater. adaptations for terrestrial overwintering of hatchlings in northern regions, where winter thermal and hydric regimes are harsh, have not been systematically investigated in many species. we measured intrinsic supercooling capacity, resistance to inoculative freezing, and desiccation resistance in hatchlings of terrestrial and aquatic turtles collected from northern (terrapene ornata, chrysemys ...200811436135
seasonal changes in physiology and development of cold hardiness in the hatchling painted turtle chrysemys picta.hatchling painted turtles (chrysemys picta) commonly hibernate in shallow, natal nests where winter temperatures may fall below -10 degrees c. although hatchlings are moderately freeze-tolerant, they apparently rely on supercooling to survive exposure to severe cold. we investigated seasonal changes in physiology and in the development of supercooling capacity and resistance to inoculative freezing in hatchling chrysemys picta exposed in the laboratory to temperatures that decreased from 22 to 4 ...200011044384
water relations of pliable-shelled eggs of common snapping turtles (chelydra serpentina). 19807427826
the rate of conversion of [14-(14)c]pregnenolone to [4-(14)c]progesterone by corpora lutea of the snapping turtle, chelydra serpentina. 19807419051
aerial and aquatic oxygen uptake by freely-diving snapping turtles (chelydra serpentina).aerial oxygen consumption of unrestrained, freely-diving warm-and cold-acclimated snapping turtles, chelydra serpentina, was measured at 10, 20, and 30°c. also, simultaneous determinations of aerial and aquatic oxygen uptake by voluntarilydiving animals were made at 4 and 20°c. the standard rates of aerial oxygen consumption are equivalent in cold-and warm-acclimated animals in water and in cold-acclimated ones in air; these rates are all lower than those of warm-acclimated animals in air. thus ...198028309683
the effect of malnutrition on immunocompetence and whole body resistance to infection in chelydra serpentina. 1979437240
seasonal fluctuations in the plasma concentrations of progesterone and oestradiol-17 beta in the female snapping turtle (chelydra serpentina).plasma concentrations of progesterone and oestradiol-17 beta were determined by radioimmunoassay procedures in the sexually mature female snapping turtle at four different stages of the annual ovarian cycle. the highest level of progesterone in the peripheral plasma was detected during the luteal stage (june), whereas the concentration of oestradiol was highest (280 pg/ml) in may, immediately before ovulation.1979429947
chlorinated hydrocarbon concentrations in plasma of the lake erie water snake (nerodia sipedon insularum) and northern water snake (nerodia sipedon sipedon) from the great lakes basin in 1998.from the great lakes basin, concentrations of 59 congener-specific polychlorinated biphenyls (pcbs) and 14 organochlorine pesticides were measured in blood plasma of northern water snake (nerodia sipedon sipedon) and lake erie water snake (nerodia sipedon insularum), which is endangered in canada. in 1998, four male adult lake erie water snakes were sampled from pelee island, western lake erie; four male northern water snakes were sampled at little lake, about 20 km north of parry sound in centr ...200011031311
effects of maternal identity and incubation temperature on snapping turtle (chelydra serpentina) metabolism.individual variation in physiological traits may have important consequences for offspring survivorship and adult fitness. variance in offspring phenotypes is due to interindividual differences in genotype, environment, and/or maternal effects. this study examined the contributions of incubation environment, maternal effects, and clutch identity to individual variation in metabolic rates in the common snapping turtle, chelydra serpentina. we measured standard metabolic rate, as determined by oxy ...200610893169
availability of water affects organ growth in prenatal and neonatal snapping turtles (chelydra serpentina).we manipulated the amount of water that was available to prenatal and neonatal snapping turtles (chelydra serpentina) in order to assess the impact of water on growth by different organs in these animals. three treatments were used: (1) turtles that completed their incubation on a wet substrate, (2) turtles that completed their incubation on a dry substrate, and (3) turtles that spent a few days in water after completing incubation on a dry substrate. turtles hatching on a dry substrate (treatme ...200010707327
the relationship of body size to survivorship of hatchling snapping turtles (chelydra serpentina): an evaluation of the "bigger is better" hypothesis.in many organisms, body size is positively correlated with traits that are presumably related to fitness. if directional selection frequently favors larger offspring (the "bigger is better" hypothesis), the results of such selection should be detectable with field experiments. we tested the "bigger is better" hypothesis in hatchling snapping turtles (chelydra serpentina) by conducting one long-term and three short-term experiments on the university of michigan e.s. george reserve in southeastern ...199928308562
fine structure of the chromophobe in the pars distalis of the common snapping turtle, chelydra serpentina.chromophobes of the pars distalis in young chelydra serpentina have sparse cytoplasm with no specific granules; however, many cytoplasmic filaments are present. the chromophobes are connected to the other cell types by desmosomes, while different types of junctional specializations occur between adjacent chromophobes. cytoplasmic filaments traverse the cytoplasm in a random manner and terminate on both the junctional complexes and the nuclear envelope. it is proposed that, in addition to providi ...19761248046
embryonic temperature affects metabolic compensation and thyroid hormones in hatchling snapping turtles.temperature acclimation of adult vertebrates typically induces changes in metabolic physiology. during early development, such metabolic compensation might have profound consequences, yet acclimation of metabolism is little studied in early life stages. we measured the effect of egg incubation temperature on resting metabolic rate (rmr) and blood thyroid hormone levels of hatchling snapping turtles (chelydra serpentina). like many reptiles, snapping turtles have temperature-dependent sex determi ...200710521320
endogenous yolk steroid hormones in turtles with different sex-determining mechanisms.maternal transfer of nutrients, including steroid hormones, to embryos during gestation in viviparous amniotes is well known, but the concordant process in oviparous amniotes is poorly understood. recent evidence suggests that steroid hormones are present in freshly laid eggs of archosaurs and that their concentrations may influence offspring phenotypes. this process might be especially important in reptiles with temperature-dependent sex determination (tsd), because embryonic sex determination ...19989707477
the graft-versus-host reaction in the snapping turtle chelydra serpentina. 19734148147
lymphoid tissue in the snapping turtle, chelydra serpentina. 19724638093
structure and development of the optic tectum of the snapping turtle (chelydra serpentina l.). 19715132820
survival of xenogeneic grafts of embryonic pigment and carapace rudiments in embryos of chelydra serpentina. 19704922223
extirpation experiments on embryonic rudiments of the carapace of chelydra serpentina. 19705482414
twinning in the common snapping turtle, chelydra serpentina. 19705461766
eimeria chelydrae n. sp. (protozoa: eimeriidae) from the snapping turtle, chelydra serpentina. 19695388988
the maturation of the capacity to reject skin allografts and xenografts in the snapping turtle, chelydra serpentina. 19694893941
a series of stages in the embryonic development of chelydra serpentina. 19685681661
motility of the turtle embryo, chelydra serpentina (linné).periodic motility of turtle embryos was observed during their incubation periods (60 +/- 5 days). cyclic activity was first observed between days 10 to 14; it increased to a peak level of 50 percent of the standard observation period on day 30 +/- 5, then declined to low levels until hatching activities were initiated. during the first third of the incubation period, motility of the turtles closely resembled that previously described for chick embryos at similar stages of development.19675212408
depletions in the cervical and thoracolumbar sympathetic system following removal of neural crest from the embryo of chelydra serpentina. 19665969768
primary structure of the cytochrome c from the snapping turtle, chelydra serpentina. 19665968568
food imprinting in the snapping turtle, chelydra serpentina.three groups of hatchling snapping turtles, totaling 20, were fed either meat, fish, or worms. when they were tested for preference after 12 daily feedings, each preferred the diet to which it was accustomed. after 12 more days of eating a different food, each still preferred its original diet. a form of imprinting may be operative in the feeding behavior of this species.19665908961
experimental studies on the columella-capsular interrelationship in the turtle chelydra serpentina. 19655861722
an experimental approach to the development of ear capsule in the turtle, chelydra serpentina. 196514329484
hypoxia: effects on heart rate and respiration in the snapping turtle.in response to atmospheres containing decreasing amounts of oxygen, snapping turtles (chelydra serpentina) maintained a fairly constant oxygen uptake. their heart rate increased and the period of apnea between breathing cycles decreased. small animals had a slightly greater mean uptake per gram than those five to ten times as large.196314014707
analysis of vagal and cholinesterase effects on the heart of chelydra serpentina. 195813606222
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