Publications

action of sex steroid hormones on temperature-induced sex determination in the snapping turtle (chelydra serpentina).	administration of exogenous estradiol benzoate (eb) or an estrogen agonist, r2858, into eggs of snapping turtles caused all embryos incubated at male-producing temperatures to develop as females, whereas testosterone propionate (tp) caused 42% of the embryos to develop as females. some of the embryos treated with eb, r2858, or tp also had hypertrophied oviducts. neither dihydrotestosterone (dht) nor cholesterol had any apparent effect on the sex determination of embryos incubated at male-produci ...	1989	2599345
factors terminating nonventilatory periods in the turtle, chelydra serpentina.	pao2, paco2 and pha were measured via an extracorporeal loop in conscious snapping turtles (chelydra serpentina) breathing air or hypoxic (10, 15% o2), hyperoxic (30% o2), or hypercapnic (2% co2) gases. turtles breathed into an inverted funnel ventilated with the test gas. breathing was recorded with a differential pressure transducer. in all turtles, nonventilatory periods were interrupted by breathing episodes containing multiple breaths. in normoxia, pao2 at the end of nonventilatory periods ...	1989	2506623
control of metabolism and growth in embryonic turtles: a test of the urea hypothesis.	we performed two experiments to determine (1) whether the metabolism and growth of embryonic snapping turtles (chelydra serpentina) incubating in wet and dry environments are correlated inversely with the concentration of urea inside their eggs, and (2) whether urea accumulating inside eggs might be the cause of reductions in metabolism and growth by embryos. eggs in the first experiment were incubated in different hydric environments to induce different patterns of net water exchange between th ...	1989	2614338
temperature dependence of in vitro pituitary, testis, and thyroid secretion in a turtle, pseudemys scripta.	in vitro culture was used to examine the direct actions of temperature at the level of pituitary hormone [luteinizing hormone (lh), thyrotropin (tsh), growth hormone (gh), prolactin (prl)] responses to neuropeptides and two related peripheral endocrine responses [thyroid hormone (t4) and testicular androgen secretion] to pituitary hormones (tsh and gonadotropins) in a turtle, pseudemys scripta. all these responses were fully suppressed at very low temperatures (5-6 degrees) and maximal near the ...	1989	2512196
development of the turtle carapace: implications for the evolution of a novel bauplan.	the chelonian carapace is composed of the endochondral ribs and vertebrae associated with a specialized dermis. the ribs are found in an aberrant position compared to those of all other tetrapods; they are superficial and dorsal to the limb girdles. this morphological arrangement, which constitutes the unique chelonian bauplan, is examined from a developmental perspective. embryos of chelydra serpentina were studied during stages of carapace development. tissue morphology, autoradiography, and i ...	1989	29865619
brain peptide yy receptors: highly conserved characteristics throughout vertebrate evolution.	we have shown previously that peptide yy (pyy) receptors are uniquely distributed in various mammalian brains and also have identified the receptor from porcine hippocampal membranes as a protein of 50,000 mol wt. to extend these observations, both the characteristics of pyy-receptor interaction and the structure of the receptor have been examined and compared with those of its sister peptide, neuropeptide y (npy), in the brains of various vertebrates including mammals (human, dog, guinea pig, r ...	1991	1657579
the case for a cause-effect linkage between environmental contamination and development in eggs of the common snapping turtle (chelydra s.serpentina) from ontario, canada.	concentrations of polychlorinated biphenyls (pcbs), dibenzo-p-dioxins, and dibenzofurans, organochlorine pesticides, and their metabolites were measured in eggs of the common snapping turtle (chelydra s.serpentina) collected from four wetlands on the shorelines of lakes ontario, and erie, and one control location in central ontario, canada. snapping turtle eggs from these sites were also artificially incubated to determine hatching success, and incidence of deformities in embryo and hatchling tu ...	1991	1908525
a phylogenetic and biogeographic analysis of the genera of spirorchinae (digenea: spirorchidae) parasitic in freshwater turtles.	cladistic analysis of the freshwater genera of spirorchinae (schistosomatoidea: spirorchidae sensu yamaguti, 1971) plus haematotrema stunkard, 1923, and aphanospirorchis platt, 1990, was completed. the spirorchinae were considered monophyletic based on synapomorphies of the esophagus. three lineages, spirhapalum (europe/asia), plasmiorchis+hemiorchis (india), and spirorchis + henotosoma + haematotrema + aphanospirorchis (north america), were identified. nelsen consensus analysis was used as the ...	1992	1635020
alternative leech vectors for frog and turtle trypanosomes.	trypanosoma pipientis infections were achieved by exposing laboratory-raised bullfrog tadpoles (rana catesbeiana) to the leech desserobdella picta that had fed on infected frogs. likewise, a laboratory-raised snapping turtle (chelydra serpentina) was infected with trypanosoma chrysemydis following exposure to infected placobdella ornata. transmission of the trypanosomes by these leeches constitutes new vector records for the parasites. the biology of d. picta and p. ornata suggests that they are ...	1992	1597811
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 ...	1992	1592234
phylogeny of regulatory regions of vertebrate tyrosinase genes.	highly homologous dna elements were found to be shared by the upstream regions of the mouse tyrosinase and tyrosinase related protein (trp-1) genes. several nuclear proteins were shown to bind to both of these upstream regions. shared homologous dna elements were also found in the 5' flanking sequences of japanese quail and snapping turtle tyrosinase genes. shared homologous nucleotide sequences were found to be scattered like an archipelago in the 5' upstream regions of mouse and human tyrosina ...	1992	1292011
purification and properties of alligator mississipiensis cytochrome c.	cytochrome c has been purified to homogeneity from alligator liver (alligator mississipiensis) using aluminum sulfate precipitation, cm-cellulose and gel-filtration chromatography, and reverse-phase hplc. the protein exhibited a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an approximate molecular weight of 12,000 da. oxidized and reduced visible spectra yielded maxima at 408 (tau) nm and 315 (delta), 415 (tau), 520 (beta), and 550 (alpha) nm, respectively, while ...	1993	8384830
comparative studies of thyroxine binding proteins in turtle plasma using column chromatography.	thyroxine (t4) binding proteins in turtle plasma were compared with those of various mammalian and nonmammalian (fish, birds) species using gel filtration chromatography (bio-gel). high-affinity t4 binding was observed in all mammals studied, in the chicken, and in one species of turtle, trachemys scripta. this high affinity t4 binding protein (tbp) appears to be the major component of t4 transport in the turtle; selective removal of this tbp greatly diminished binding activity in t. scripta pla ...	1993	8428644
binding affinities of thyroxine-binding proteins in turtle plasma.	binding affinities (ka) for thyroxine (t4) by blood plasma and purified plasma proteins from two turtles, the slider (trachemys scripta) and snapper (chelydra serpentina), were compared with those of a human using equilibrium dialysis. the purified t4 binding protein (tbp) from t. scripta had a high affinity that was lower by about fivefold than that of human tbg (3.2 x 10(9) vs 1.7 x 10(10) m-1). the affinity of t4 binding by tbp was similar to that determined for whole plasma from this species ...	1993	8504925
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 ...	1993	28313447
temperature-dependent sex determination in the snapping turtle: manipulation of the embryonic sex steroid environment.	in certain reptiles with temperature-dependent sex determination (tsd), estrogens act as a signal for female differentiation. because aromatase produces estrogens from androgens, this enzyme plays a pivotal role in tsd. whether androgens act as the signal for male differentiation in tsd species in not yet clear. we manipulated the hormonal environment in eggs of the common snapping turtle (chelydra serpentina) to determine the effects of an estrogen (estradiol 17-beta), an aromatase inhibitor (f ...	1994	7851724
the amino acid sequence of iguana (iguana iguana) pancreatic ribonuclease.	the pyrimidine-specific ribonuclease superfamily constitutes a group of homologous proteins so far found only in higher vertebrates. four separate families are found in mammals, which have resulted from gene duplications in mammalian ancestors. to learn more about the evolutionary history of this superfamily, the primary structure and other characteristics of the pancreatic enzyme from iguana (iguana iguana), a herbivorous lizard species belonging to the reptiles, have been determined. the polyp ...	1994	8307028
molecular mechanisms of tsd in reptiles: a search for the magic bullet.	significant progress has been made in understanding mechanisms of genetic sex determination. the zfy gene encodes a zinc finger protein but is not the primary signal in sex determination. the sry gene is the testis determining gene in man, mouse, rabbit, and probably marsupial mouse and wallaby. temperature dependent sex determination probably involves a modification of development of the indifferent gonad due to differential expression of one or more specific dna sequences whose behavior is con ...	1994	7931129
sequence analysis of the zfy and sox genes in the turtle, chelydra serpentina.	we have sequenced regions of the zfy and sox genes in the turtle chelydra serpentina, a reptile with temperature-dependent sex determination. the zfy gene in mammals encodes a transcription factor with multiple zinc fingers that may be involved in spermatogenesis as well as other processes. the turtle homologue, zft, is 92% identical to the zfy gene at the nucleotide and amino acid levels in the region of zinc fingers 7-12. there are several sox genes in the turtle that are only 57-70% identical ...	1994	8025725
dermatophilus chelonae sp. nov., isolated from chelonids in australia.	three isolates of a previously undescribed dermatophilus sp. obtained from chelonids (two strains obtained from turtles and one strain obtained from a tortoise) were compared with 30 dermatophilus congolensis isolates obtained from australian mammals. the microscopic appearance, the colony morphology, and most biochemical test results for the chelonid isolates were characteristic of the genus dermatophilus. our isolates differed from the mammalian d. congolensis isolates in a number of cultural ...	1995	7857807
lipid provisioning of turtle eggs and hatchlings: total lipid, phospholipid, triacylglycerol and triacylglycerol fatty acids.	lipid composition of eggs and hatchlings was studied in painted, snapping and blanding's turtles from western nebraska. the average total lipid proportions of the egg yolk, post-embryonic yolk and hatchling soma dry masses were high in painted turtles (29.80%, 42.16% and 14.18%, respectively) relative to snapping and blanding's turtles (egg yolk < 14%, postembryonic yolk < 17%, hatchling soma < 2%). the proportion of total egg yolk lipid used during development varied among species (painted turt ...	1995	7584861
experimental evidence for the evolutionary significance of temperature-dependent sex determination.	the evolutionary significance of sex-determining mechanisms, particularly temperature-dependent sex determination (tsd) in reptiles, has remained unresolved despite extensive theoretical work. to investigate the evolutionary significance of this unusual sex-determining mechanism, i incubated eggs of the common snapping turtle (chelydra serpentina) at a male-producing temperature (26°c), a female-producing temperature (30°c), and an intermediate temperature that produced both sexes about equally ...	1995	28564861
heart rate during development in the turtle embryo: effect of temperature.	growth and development can occur over a wide range of physical conditions in reptiles. cardiovascular function must be critical to this ability. however, information on cardiovascular function in developing reptiles is lacking. previous work indicated that in reptiles the effects of temperature on growth and metabolism are largely restricted to early development. this study examined whether the previously observed effects of temperature and different perinatal patterns of metabolism observed in ...	1996	8981759
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 ...	1996	8975824
comparative effects of diverse vertebrate gonadotropins on estradiol-17 beta formation in vitro in an immature rat sertoli cell bioassay.	the biopotencies of pituitary gonadotropins (gths) from various vertebrate classes were examined in an in vitro rat sertoli cell bioassay which was previously established for mammalian follicle-stimulating hormones (fshs). potencies of the gonadotropins were determined by incubation of sertoli cells obtained from 10-day-old rats, with increasing doses of gths, which resulted in dose-related and parallel estradiol-17 beta formation converted from added 19-hydroxy-androstenedione. in general, mamm ...	1996	8930616
purification and characterization of plasma vitamin d binding protein from the snapping turtle, chelydra serpentina.	vitamin d binding protein (dbp) was isolated from the plasma of the snapping turtle, chelydra serpentina (mixed sex adult), and compared with the previously characterized dual function binding plasma protein that binds both thyroxine (t4) and vitamin d (tstdbp) in an emydid turtle, trachemys scripta. purification of chelydra serpentina dbp (csdbp) was accomplished by ion exchange chromatography, preparative polyacrylamide gel electrophoresis, and reverse-phase high-performance liquid chromatogra ...	1996	8954770
the regulation of tyrosinase gene transcription.	tyrosinase is one of the key enzymes essential for melanogenesis. the control of its activity rests in part at the level of transcriptional regulation. the 5' promoter regions of the human, mouse, chicken, quail, snapping turtle, and frog tyrosinase sequences have been isolated and the mechanisms regulating the activity of these sequences are beginning to be elucidated. this review provides an update on the following aspects of tyrosinase gene regulation: basal promoter elements that determine t ...	1997	9266599
lead poisoning and intestinal perforations in a snapping turtle (chelydra serpentina) due to fishing gear ingestion.	an adult male snapping turtle (chelydra serpentina) was presented to the tufts wildlife clinic with generalized weakness and limited ability to walk. a fishing hook was lodged in the corner of its mouth, monofilament line trailed from its cloaca, and radiography revealed that the turtle had ingested two additional hooks and a large sinker. the hemogram showed leukocytosis. at exploratory celiotomy, the fishing line was seen to have acted as a linear foreign body and had perforated the intestines ...	1997	9226626
purification and partial amino acid sequences of two distinct albumins from turtle plasma.	two putative albumins, denoted alb-1 (apparent molecular mass of 67 kda) and alb-2 (68 kda), were purified from plasma of the emydid turtle (trachemys scripta). concentrations in serum or plasma were determined by radioimmunoassay using 125i-labeled alb-1. in juvenile turtles (less than 2 years of age), serum concentrations of alb-1 and alb-2 were 2.72 +/- 0.23 mg/ml and 1.68 +/- 0.22 mg/ml, respectively, while concentrations in plasma pooled from adult turtles were 4.2 mg/ml and 2.6 mg/ml, resp ...	1997	9440230
abundant synthesis of transthyretin in the brain, but not in the liver, of turtles.	the binding of thyroxine to proteins in the blood plasma of the turtle, trachemys scripta, was analyzed by incubation with radioactive thyroxine, electrophoresis and autoradiography. albumin and an alpha-globulin were found to bind thyroxine; no thyroxine-binding transthyretin was detected in the prealbumin region. in contrast to blood plasma, a thyroxine-binding prealbumin was observed in medium from t. scripta choroid plexus incubated in vitro. rna was extracted from brain tissue containing ch ...	1997	9253180
seasonal changes in gonadal activity and the effects of stress on reproductive hormones in the common snapping turtle, chelydra serpentina.	the seasonal gonadal cycle (including gonadal histology, sex steroids, and gonadotropins) was studied in freshly captured common snapping turtles, chelydra serpentina, from wisconsin, and the effects of capture stress were evaluated. the ovarian and testicular cycles are shorter than those reported in other freshwater turtles; the cycles commence in mid-may and terminate in early september, immediately after the completion of gonadal growth and maturation. in the female, testosterone (t), 17beta ...	1997	9268617
hematology and clinical chemistry reference ranges for clinically normal, captive new guinea snapping turtle (elseya novaeguineae) and the effects of temperature, sex, and sample type.	median values and confidence intervals for hematology and serum and plasma chemistry parameters were established for 29 male and female healthy new guinea snapping turtles (elseya novaeguineae) held at 24.5 degrees c and 30.0 degrees c. creatine kinase, albumin, potassium, and phosphorus values were significantly higher at 24.5 degrees c than at 30.0 degrees c. glucose, alkaline phosphatase, aspartate transaminase, alanine aminotransferase, total carbon dioxide, and chloride values were signific ...	1997	9523632
impact of organochlorine contamination on levels of sex hormones and external morphology of common snapping turtles (chelydra serpentina serpentina) in ontario, canada.	recent research has suggested that contaminants in the environment may influence sex differentiation and reproductive endocrine function in wildlife. concentrations of organochlorine contaminants (total polychlorinated biphenyls, pesticides) were higher in the blood plasma of snapping turtles from contaminated sites than in those from reference sites. the ratio of the precloacal length to the posterior lobe of the plastron (ppr) is sexually dimorphic in snapping turtles. there were significant r ...	1998	9518475
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 ...	1998	9503646
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 ...	1998	9427676
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 ...	1998	15093107
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 ...	1998	9707477
kinematics of aquatic and terrestrial prey capture in terrapene carolina, with implications for the evolution of feeding in cryptodire turtles.	studies of aquatic prey capture in vertebrates have demonstrated remarkable convergence in kinematics between diverse vertebrate taxa. when feeding in water, most vertebrates employ large-amplitude hyoid depression to expand the oral cavity and suck in water along with the prey. in contrast, vertebrates feeding on land exhibit little or no hyoid depression. in this study we compared the kinematics of terrestrial and aquatic prey capture within one species of turtle, terrapene carolina, in order ...	1998	9658591
chelonacarus elongatus n. gen., n. sp. (acari: cloacaridae) from the cloaca of the green turtle chelonia mydas (cheloniidae).	chelonacarus elongatus n. gen., n. sp. is proposed for a cheyletoid mite (acari: prostigmata) of the family cloacaridae found in the cloacal tissue of the endangered green turtle chelonia mydas linnaeus, 1758 from the atlantic coast of the republic of panama. in females, the new genus is distinguished from other genera of turtle cloacarids by the elongate slender shape of the idiosoma, the shape and pattern of sclerotization of the dorsal shield, and the fused distal ends of apodemes ii. a combi ...	1998	9714221
environmental occurrence and potential toxicity of planar, mono-, and di-ortho polychlorinated biphenyls in the biota.	four non-ortho-, eight mono-ortho-, and two di-ortho-chlorinated congeners have been determined in fresh water and salt water mussels, fish, snapping turtles, mallard, seals, and in human milk and adipose tissue. the planar pcb congeners are separated from the remainder of pcbs by activated carbon chromatography or hplc on porous graphitic carbon followed by gas chromatography with electron capture detection. pcb toxic equivalency factors (tefs) recommended by who [1] for 3 non-ortho, 8 mono-ort ...	1998	9503581
among-family variation for environmental sex determination in reptiles.	unlike birds and mammals, in many reptiles the temperature experienced by a developing embryo determines its gonadal sex. to understand how temperature-dependent sex determination (tsd) evolves, we must first determine the nature of genetic variation for sex ratio. here, we analyze among-family variation for sex ratio in three tsd species: the american alligator (alligator mississipiensis), the common snapping turtle (chelydra serpentina) and the painted turtle (chrysemys picta). significant fam ...	1998	28565384
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 ...	1999	10381306
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 ...	1999	28308562
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 ...	2000	10707327
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 ...	2000	11044384
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 ...	2000	11031311
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 ...	2000	10936762
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.	2000	10745125
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 ...	2001	11748616
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.	2001	11695407
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 ...	2001	11683228
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 ...	2001	11443374
wildlife as sentinels of human health effects in the great lakes--st. lawrence basin.	there is no existing formal, long-term program for gathering evidence of the incidence and severity of the health effects of toxic substances in wildlife. however, research-based studies of bald eagles, herring gulls, night herons, tree swallows, snapping turtles, mink, and beluga over the past 30 years have revealed a broad spectrum of health effects in the great lakes-st. lawrence basin including thyroid and other endocrine disorders, metabolic diseases, altered immune function, reproductive i ...	2001	11744503
functional conservation of the promoter regions of vertebrate tyrosinase genes.	tyrosinase is the key enzyme for synthesizing melanin pigments, which primarily determine mammalian skin coloration. considering the important roles of pigments in the evolution and the adaptation of vertebrates, phylogenetic changes in the coding and flanking regulatory sequences of the tyrosinase gene are particularly intriguing. we have now cloned cdna encoding tyrosinase from japanese quail and snapping turtle. these nonmammalian cdna are highly homologous to those of the mouse and human tyr ...	2001	11764277
development of the pulmonary surfactant system in non-mammalian amniotes.	pulmonary surfactant (ps) is a complex mixture of phospholipids, neutral lipids and proteins that lines the inner surface of the lung. here, it modulates surface tension thereby increasing lung compliance and preventing the transudation of fluid. in mammals, the ps system develops towards the end of gestation, characterized by an increase in the saturation of phospholipids in lung washings and the appearance of surfactant proteins in amniotic fluid. birth, the transition from in utero to the ext ...	2001	11369533
comparison and evolution of the lagena in various animal species.	the structure of the vestibular organs of the teleost fish (bluegill), newts (japanese fire-belly newt), frogs (black-spotted pond frog), snapping turtles and birds (chicks) was morphologically compared, with particular attention to the lagena macula, and the differences between animal species with relation to evolution were considered. teleost fish had no striola on the lagena macula. the striola of newts were short and restricted to the central area of the macula, but those of frogs, snapping ...	2001	11425201
cross-species investigations of prenatal experience, hatching behavior, and postnatal behavioral laterality.	turning biases have been reported in some mammalian species, but less is known about such biases in nonmammalians. this study investigated turning biases in domestic chicks, bobwhite and japanese quail, leopard geckos, and snapping turtles. domestic chicks (white leghorn and bantam) and bobwhite quail demonstrate strong group laterality. japanese quail chicks, snapping turtles, and leopard geckos demonstrate no significant group bias. results are discussed with regard to differences in embryonic ...	2001	11568878
octylphenol (op) alters the expression of members of the amyloid protein family in the hypothalamus of the snapping turtle, chelydra serpentina serpentina.	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 o ...	2002	11882478
morbidity and mortality of reptiles admitted to the wildlife center of virginia, 1991 to 2000.	medical records from 694 reptiles admitted to the wildlife center of virginia (wcv; waynesboro, virginia, usa) from 1991 to 2000 were reviewed to determine causes of morbidity and mortality. eighteen species were represented but the majority of cases were four species; eastern box turtle (terrapene carolina) (66%), eastern painted turtle (chrysemys picta) (11%), common snapping turtle (chelydra serpentina) (10%), and rat snake (elaphe sp.) (6%). there was a significant increase in reptile cases ...	2002	12528435
comparative patterns of postcranial ontogeny in therian mammals: an analysis of relative timing of ossification events.	data on the relative sequence of ossification of postcranial elements for eight therian mammals (myotis lucifugus, homo sapiens, rattus norvegicus, mus musculus, mesocricetus auratus, cavia porcellus, didelphis albiventris, and sminthopsis macroura) and three outgroups (chelydra serpentina, alligator mississippiensis, and lacerta vivipara) were taken from the literature. for each species, a matrix was constructed in which the relative timing of the onset of ossification in 24 elements was summar ...	2002	12362432
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 ...	2002	11854378
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 ...	2002	12013138
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 ...	2002	12161198
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 ...	2002	12095870
dynamics of yolk steroid hormones during development in a reptile with temperature-dependent sex determination.	many oviparous reptiles exhibit temperature-dependent sex determination (tsd); i.e., the temperature at which the egg is incubated determines the sex of the offspring. in tsd reptiles, yolk steroids not only may influence sex determination, but also may mediate hormonal effects on subsequent growth and behavior, as in some avian species. we investigated changes in the levels of estradiol (e(2)) and testosterone (t) during development in yolks of snapping turtle eggs, examined how incubation temp ...	2002	12161199
a high standard metabolic rate constrains juvenile growth.	the allocation of energy to various components of an individual's energy budget is often viewed as a competitive process. as such, a tradeoff may exist between production (growth) and maintenance metabolism. one view of a potential tradeoff, termed "the principle of allocation", suggests that individuals with lower maintenance metabolic expenditures may have higher growth rates. to determine whether such a tradeoff exists, i analyzed the relationship between growth rate and maintenance metabolis ...	2002	16351863
ranking terrestrial vertebrate species for utility in biomonitoring and vulnerability to environmental contaminants.	the measurement of contaminant tissue concentrations or exposure-related effects in biota has been used extensively to monitor pollution and environmental health. terrestrial vertebrates have historically been an important group of species in such evaluations, not only because many are excellent sentinels of environmental contamination, but also because they are valued natural resources in their own right that may be adversely affected by toxicant exposure. selection of appropriate vertebrates f ...	2003	12442504
acanthostomum macroclemidis n. sp. (digenea: cryptogonimidae: acanthostominae) from the alligator snapping turtle, macroclemys temmincki.	acanthostomum macroclemidis n. sp. is described from specimens found in the intestine of an alligator snapping turtle macroclemys temmincki from southern mississippi. the most important diagnostic features of the new species are the general shape and proportions of the body, the position of the pharynx (relative length of the prepharynx and esophagus), the egg size, the relative length and position of the vitelline fields, and the number, shape, and size of the circumoral spines. the new species ...	2003	12659321
[requirements for the keeping of dangerous exotic animals].	the problem of dangerous dogs receives a lot of public attention. however, there is another group of animals that can threaten public security--the group of dangerous exotic animals. in daily routine mainly venomous snakes, spiders and scorpions or crocodiles, giant snakes and snapping turtles are of practical importance. the paper gives hints how to keep these animals according to animal protection and public safety rules.	2003	12822263
yolk steroid hormones and sex determination in reptiles with tsd.	in reptiles with temperature-dependent sex determination (tsd), the temperature at which the eggs are incubated determines the sex of the offspring. the molecular switch responsible for determining sex in these species has not yet been elucidated. we have examined the dynamics of yolk steroid hormones during embryonic development in the snapping turtle, chelydra serpentina, and the alligator, alligator mississippiensis, and have found that yolk estradiol (e(2)) responds differentially to incubat ...	2003	12849957
osteology and skeletal development of apalone spinifera (reptilia: testudines: trionychidae).	despite considerable attention that other groups of reptiles have received, few descriptions of the development and sequences of chondrification and ossification of the entire skeleton of turtles exist. herein, the adult skeleton of the spiny softshell turtle, apalone spinifera (testudines: trionychidae), is described; this description forms a basis of comparison for the embryonic skeleton and its ontogenesis. descriptions are made on the basis of cleared and double-stained embryos and dry skele ...	2003	12616574
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 ...	2003	12927492
absence of detectable salmonella cloacal shedding in free-living reptiles on admission to the wildlife center of virginia.	salmonellosis is an important reptile-associated zoonotic infection in the united states. cloacal swabs were collected from reptiles admitted to the wildlife center of virginia, waynesboro, virginia, cultured for salmonella using hektoen and xylose lysine deoxycholate agars, and inoculated in selenite broth. all three were incubated at 37 degrees c for 18-24 hr. seventy-five animals were included in the study, representing eight species, 34 eastern box turtles (terrapene carolina carolina), 14 e ...	2004	15732603
redescription of dracunculus globocephalus mackin, 1927 (nematoda: dracunculidae), a parasite of the snapping turtle, chelydra serpentina.	dracunculus globocephalus mackin, 1927 (nematoda: dracunculoidea) is redescribed from specimens collected from the mesentery of the snapping turtle, chelydra serpentina (l.), in louisiana, usa. the use of scanning electron microscopy, applied for the first time in this species, made it possible to study details in the structure of the cephalic end and the arrangement of male caudal papillae that are difficult to observe under the light microscope. this species markedly differs from all other spe ...	2004	15729947
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 ...	2004	15596394
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 ...	2004	14743515
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 ...	2004	15276278
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 ...	2004	15235017
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 ...	2004	15305520
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.	2004	15562628
report of dysgerminoma in the ovaries of a snapping turtle (chelydra serpentina) with discussion of ovarian neoplasms reported in reptilians and women.	a malnourished, captive, young adult (weight-11 kg, carapace length-25 cm), female snapping turtle (chelydra serpentina) was presented for examination and treatment of malnutrition and multiple carapace necroses. because treatment was unsuccessful, the animal was euthanatized and necropsied. the main necropsy observations showed the presence of a 9 cm greyish-white/yellow, soft, fleshy to fatlike mass involving the right ovary near the oviduct opening and multiple similar, pea-to-walnut sized ma ...	2004	1520837
contaminant residues in snapping turtle (chelydra s. serpentina) eggs from the great lakes-st. lawrence river basin (1999 to 2000).	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 riv ...	2004	15386150
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 ...	2005	15536645
perfluorinated compounds in aquatic organisms at various trophic levels in a great lakes food chain.	trophic transfer of perfluorooctanesulfonate (pfos) and other related perfluorinated compounds was examined in a great lakes benthic foodweb including water-algae-zebra mussel-round goby-smallmouth bass. in addition, perfluorinated compounds were measured in livers and eggs of chinook salmon and lake whitefish, in muscle tissue of carp, and in eggs of brown trout collected from michigan. similarly, green frog livers, snapping turtle plasma, mink livers, and bald eagle tissues were analyzed to de ...	2005	15883668
characterization of a ribonuclease gene and encoded protein from the reptile, iguana iguana.	in this work we identify an intronless open reading frame encoding an rnase a ribonuclease from genomic dna from the iguana iguana igh2 cell line. the iguana rnase is expressed primarily in pancreas, and represents the majority of the specific enzymatic activity in this tissue. the encoded sequence shares many features with its better-known mammalian counterparts including the crucial his12, lys40 and his114 catalytic residues and efficient hydrolytic activity against yeast trna substrate (k(cat ...	2005	15893436
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 ...	2005	15739066
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 ...	2006	16758216
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 ...	2006	16360253
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 ...	2006	16360251
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%). ...	2006	1674911
intramembranous ossification of scleral ossicles in chelydra serpentina.	scleral ossicles are present in many reptiles, including turtles and birds. in both groups the sclerotic ring situated in the eye is composed of a number of imbricating scleral ossicles or plates. despite this gross morphological similarity, andrews (1996. an endochondral rather than a dermal origin for scleral ossicles in cryptodiran turtles. j. herpetol. 30, 257-260) reported that the scleral ossicles of turtles develop endochondrally unlike those in birds, which develop intramembranously afte ...	2006	16377163
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, ...	2006	16583258
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 ...	2006	16519315
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 ...	2006	16384588
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 ...	2006	10893169
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 ...	2006	10603335
the complete mitochondrial genome of the enigmatic bigheaded turtle (platysternon): description of unusual genomic features and the reconciliation of phylogenetic hypotheses based on mitochondrial and nuclear dna.	the big-headed turtle (platysternon megacephalum) from east asia is the sole living representative of a poorly-studied turtle lineage (platysternidae). it has no close living relatives, and its phylogenetic position within turtles is one of the outstanding controversies in turtle systematics. platysternon was traditionally considered to be close to snapping turtles (chelydridae) based on some studies of its morphology and mitochondrial (mt) dna, however, other studies of morphology and nuclear ( ...	2006	16464263
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 ...	2007	10521320
high-resolution analysis of salmonellae from turtles within a headwater spring ecosystem.	sediments and water from the pristine headwaters of the san marcos river, texas, usa, as well as swabs from biofilms on the carapace and from the cloacae of 17 musk turtles (sternotherus odoratus) and one snapping turtle (chelydra serpentina serpentina) caught at the same site, were analysed for salmonellae by culture and molecular techniques. whereas enrichment cultures from sediment and water samples were negative for salmonellae in pcr- and in situ hybridization-based analyses, both technique ...	2007	17250751
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 ...	2007	18391536