Publications

agricultural land use creates evolutionary traps for nesting turtles and is exacerbated by mercury pollution.	the rate of anthropogenic habitat conversion often exceeds the rate of natural ecological and evolutionary processes, which sometimes creates mismatches between environmental cues and adaptive behaviors. in numerous species of aquatic turtles, nest site selection is primarily based on cues related to high solar exposure, which leads females to select sites where humans have disturbed habitat. these disturbed sites are often contaminated by pollutants, such as mercury. despite the fact that anthr ...	2018	29962084
the development and homology of the chelonian carpus and tarsus.	the long-standing controversies involving the number and homologies of the elements of the carpus and tarsus of turtles are reviewed from a developmental perspective. the analysis is based on a detailed description of the chondrogenesis of the carpus and tarsus in the species chelydra serpentina and chrysemys picta. the first stage described is the differentiation of a y-shaped chondrogenetic condensation involving the humerus (femur)-radius/ ulna (tibia/fibula). this stage is followed by the ea ...	1985	30005563
convective oxygen transport during development in embryos of the snapping turtle chelydra serpentina.	this study investigated the maturation of convective oxygen transport in embryos of the snapping turtle (chelydra serpentina). measurements included: mass, oxygen consumption (v̇o2 ), heart rate, blood oxygen content and affinity and blood flow distribution at 50%, 70% and 90% of the incubation period. body mass increased exponentially, paralleled by increased cardiac mass and metabolic rate. heart rate was constant from 50% to 70% incubation but was significantly reduced at 90% incubation. hema ...	2018	30065037
using non-destructive techniques to measure mercury (hg) concentrations in gravid blanding's turtles (emydoidea blandingii) in northeastern illinois.	aquatic turtles are suitable biomonitors of wetland ecosystem health because they are long-lived and occupy elevated trophic positions in wetland food webs. this study aimed to determine hg exposure in adult blanding's turtles (emydoidea blandingii), an imperiled prairie-wetland species endemic to the northern u.s. and southern canada. claw samples were collected from gravid females from four wetland sites in northeast illinois. claw hg concentrations ranged from 654 to 3132 ng/g and we found no ...	2018	30073403
substituted diphenylamine antioxidants and benzotriazole uv stabilizers in blood plasma of fish, turtles, birds and dolphins from north america.	substituted diphenylamine antioxidants (sdpas) and benzotriazole uv stabilizers (bzt-uvs) are additives used in industrial and commercial applications to prevent degradation by oxidation and are contaminants of emerging environmental concern. little is known about the fate of these contaminants in wildlife, particularly in reptiles, birds and marine mammals. nine sdpas and six bzt-uvs were measured in blood plasma of seven fish species, snapping turtles (chelydra serpentina), double-crested corm ...	2019	30081360
determination of temperature sensitive stages for sexual differentiation of the gonads in embryos of the turtle, emys orbicularis.	in order to determine the temperature sensitive stages for sexual differentiation of the gonads in emys orbicularis, eggs of this turtle were shifted at different stages of embryonic development from the male-producing temperature of 25°c to the female-producing temperature of 30°c and reciprocally. based on the series of developmental stages described by yntema ('68) for chelydra serpentina, temperature begins to influence sexual differentiation of emys orbicularis at stage 16, a stage in which ...	1981	30114859
colonization and usage of an artificial urban wetland complex by freshwater turtles.	conservation authorities invest heavily in the restoration and/or creation of wetlands to counteract the destruction of habitat caused by urbanization. monitoring the colonization of these new wetlands is critical to an adaptive management process. we conducted a turtle mark-recapture survey in a 250 ha artificially created wetland complex in a large north american city (toronto, ontario). we found that two of ontario's eight native turtle species (snapping turtle (sn), chelydra serpentina, and ...	2018	30123718
temperature levels and periods of sex determination during incubation of eggs of chelydra serpentina.	eggs of chelydra serpentina were shifted during incubation between the female producing temperatures of 20°c or 30°c and the male producing temperature of 26°c. in the 20°c and 26°c combination, the stages during which incubation temperature determined sex were stage 14 through stage 16 (stages of normal series, yntema, '68). in the 30°c and 26°c combination, the temperature sensitive stages for sex determination were stage 14 through stage 19. incubation at 26°c throughout this period was neede ...	1979	30205629
health assessment of free-ranging chelonians in an urban section of the bronx river, new york, usa.	the bronx river in bronx, new york, us spans an area of significant human development and has been subject to historic and ongoing industrial contamination. we evaluated the health of freeranging native common snapping turtles ( chelydra serpentina) and nonnative invasive red-eared sliders ( trachemys scripta) in a segment of the bronx river between may and july 2012. in 18 snapping turtles and nine sliders, complete physical examinations were performed, ectoparasites collected, and blood was an ...	2019	30226800
effects of incubation temperatures on sexual differentiation in the turtle, chelydra serpentina.	eggs of the common snapping turtle, chelydra serpentina, were incubated at constant temperatures ranging from 20°c to 30°c, at hatching, the oviducts were absent or incomplete in males; the testes were differentiated. in females at hatching, the oviduct was intact hut in some cases the gonad retained bisexual characteristics. three months after hatching, the ovary was differentiated and contained follicles. eggs incubated at 20°c and at 30°c developed into females in 100% of the cases. at 26°c, ...	1976	30257532
phylogenetic origins for severe acetaminophen toxicity in snake species compared to other vertebrate taxa.	while it has been known for a while that some snake species are extremely sensitive to acetaminophen, the underlying mechanism for this toxicity has not been reported. to investigate if essential detoxification enzymes are missing in snake species that are responsible for biotransformation of acetaminophen in other vertebrate species, livers were collected from a variety of snake species, together with samples from alligator, snapping turtle, cat, rat, and cattle. subcellular fractions were anal ...	2019	30268769
antibacterial activities of plasma from the common (chelydra serpentina) and alligator snapping turtle (macrochelys temminckii).	innate immunity provides a fast-acting and nonspecific defense against microbial infection, and appears to have particular importance in the immune response of ectothermic vertebrates. chelonians are a globally distributed and diverse group, yet little is known about their basic immune function. the chelonian family chelydridae is made up of two genera (chelydra and macrochelys), represented in our study by the widespread common snapping turtle ( chelydra serpentina; cst) and the southeast usa e ...	2019	30273972
incidence and progress of rejection of embryonic limb bud transplants in the turtle, chelydra serpentina.	allografts of embryonic limb buds were grafted orthotopically on embryos of chelydra serpentina. donors were from a different geographic area, the same geographic area, or siblings. the initial indication of rejection was excessive sloughing of epidermis. this was followed by loss of muscle, claws and bone. early histological changes involved an infiltration of mononuclear or rejection cells primarily associated with small blood vessels of the connective tissue. subsequently, muscle and bone wer ...	1974	30322221
survival of skin allografts following embryonic limb bud transplants in the turtle, chelydra serpentina.	allografts of skin were observed in chelydra serpentina. the response to these grafts was modified by a previous transplantation of a limb bud at an early embryonic stage. when the same donor was used for all transplants, the first skin graft was accepted by the host. a second skin graft, however, was rejected at about the rate of a simple first set allograft of skin. the animals were conditioned by the embryonic limb graft; this embryonic graft can be undergoing rejection at the same time a fir ...	1974	30326680
measurement and modelling of primary sex ratios for species with temperature-dependent sex determination.	for many oviparous animals, incubation temperature influences sex through temperature-dependent sex determination (tsd). although climate change may skew sex ratios in species with tsd, few available methods predict sex under natural conditions, fewer still are based on mechanistic hypotheses of development, and field tests of existing methods are rare. we propose a new approach that calculates the probability of masculinization (pm) in natural nests. this approach subsumes the mechanistic hypot ...	2019	30352829
identification of a novel nidovirus as a potential cause of large scale mortalities in the endangered bellinger river snapping turtle (myuchelys georgesi).	in mid-february 2015, a large number of deaths were observed in the sole extant population of an endangered species of freshwater snapping turtle, myuchelys georgesi, in a coastal river in new south wales, australia. mortalities continued for approximately 7 weeks and affected mostly adult animals. more than 400 dead or dying animals were observed and population surveys conducted after the outbreak had ceased indicated that only a very small proportion of the population had survived, severely th ...	2018	30356240
comparative cranial morphology of the late cretaceous protostegid sea turtle desmatochelys lowii.	the phylogenetic placement of cretaceous marine turtles, especially protostegidae, is still under debate among paleontologists. whereas protostegids were traditionally thought to be situated within the clade of recent marine turtles (chelonioidea), some recent morphological and molecular studies suggest placement along the stem of cryptodira. the main reason why the evolution of marine turtles is still poorly understood, is in part due to a lack of insights into the cranial anatomy of protostegi ...	2018	30568851
comparison of alligator snapping turtle ( macrochelys temminckii) plasma biochemical profiles from two clinical analyzers.	the interpretation of plasma biochemical profiles can be confounded by the methodologies by which samples are analyzed. the goal of this study was to compare agreement between two biochemical analyzers for plasma samples from alligator snapping turtles ( macrochelys temminckii). blood was obtained from the dorsal coccygeal vein of captive-reared, juvenile turtles ( n = 34), stored in lithium heparin tubes, and centrifuged to separate plasma from whole blood. plasma samples were stored at 5°c pri ...	2018	30592915
positive or negative? the shell alters the relationship among behavioral defense strategy, energy metabolic levels and antioxidant capacity in freshwater turtles.	the relationships among energy metabolic levels, behavioral and other physiological traits help to determine the trade-off of energy allocation between different traits and the evolution of life-history driven by natural selection. however, these relationships may be distinctive in selected animal taxa because of their unique traits. in the present study, the relationships among energy metabolic levels, behavioral defense strategies, and antioxidant capacity were explored in three freshwater tur ...	2019	30809267
anthropogenic nest sites provide warmer incubation environments than natural nest sites in a population of oviparous reptiles near their northern range limit.	oviposition site choice affects a host of offspring phenotypes and directly impacts maternal fitness. recent evidence suggests that oviparous reptiles often select nest sites where the landscape has been altered by anthropogenic activity, whereas natural nest sites are less often used. we leverage a long-term study of snapping turtle (chelydra serpentina) to identify natural nest sites and anthropogenic nest sites and to compare habitat variables among nest site types. natural and anthropogenic ...	2019	30953168
long term effects of chronic prenatal exposure to hypercarbia on organ growth and cardiovascular responses to adrenaline and hypoxia in common snapping turtles.	reptilian embryos often face challenging environmental gas compositions during incubation, which may inflict long-lasting effects in the individuals' physiological responses. these conditions can have a lasting effect on the animal into juvenile life as chronic prenatal exposure to hypercarbia results in enlarged hatchling organ size, higher growth rate and resting metabolic rate, although relatively smaller increment in metabolic scope during digestion. therefore, we wanted to verify whether pr ...	2019	31004807
role for androgens in determination of ovarian fate in the common snapping turtle, chelydra serpentina.	sex steroids are involved in sex determination in almost all vertebrates, including species with temperature-dependent sex determination (tsd). it is well established that aromatase and estrogens are involved in ovary determination in tsd species. in contrast, the role of non-aromatizable androgens in tsd is less clear. in this study, we used dihydrotestosterone (dht) and an antagonist of the mammalian androgen receptor (flutamide) to examine the impact of androgens on sex determination in the s ...	2019	31059691
surgical anatomy of celiotomy approaches to the stomach in the common snapping turtle (chelydra serpentina).	entanglement in or ingestion of fishing gear is a common cause of morbidity and mortality in chelonians. commercial and recreational fishing activities exert bycatch pressures sufficient to cause population declines in the common snapping turtle (chelydra serpentina) and the alligator snapping turtle (macrochelys spp.). gastrotomy for the removal of fish hook foreign bodies from the stomach of freshwater turtles typically requires a plastron osteotomy but in sea turtles has been successfully acc ...	2019	31120665
different mechanisms of serum complement activation in the plasma of common (chelydra serpentina) and alligator (macrochelys temminckii) snapping turtles.	reptiles are declining worldwide yet our understanding of their immune function lags far behind other taxa. the innate immune system is the primary mode of defense in reptiles, and the serum complement cascade is its major component. we assessed serum complement activity of plasma in two closely related aquatic turtle species, the common snapping turtle (cst; chelydra serpentina) and alligator snapping turtle (ast; macrochelys temminckii). we used a sheep red blood cell (srbc) hemolysis assay to ...	2019	31170203
first report of ranavirus mortality in a common snapping turtle chelydra serpentina.	an adult male snapping turtle with marked palpebral edema and multifocal skin ulceration was found alive in a marsh in southern ontario in summer 2017. the turtle was transported to a rehabilitation facility and died 4 d after arrival. the carcass was submitted to the canadian wildlife health cooperative for post-mortem examination. gross lesions included ulcerative conjunctivitis, necrotizing stomatitis, and splenomegaly. microscopically, this corresponded to multisystemic fibrinonecrotizing va ...	2019	31188138
developmental plasticity of cardiac anoxia-tolerance in juvenile common snapping turtles ( chelydra serpentina).	for some species of ectothermic vertebrates, early exposure to hypoxia during embryonic development improves hypoxia-tolerance later in life. however, the cellular mechanisms underlying this phenomenon are largely unknown. given that hypoxic survival is critically dependent on the maintenance of cardiac function, we tested the hypothesis that developmental hypoxia alters cardiomyocyte physiology in a manner that protects the heart from hypoxic stress. to test this hypothesis, we studied the comm ...	2019	31238852
correction: different mechanisms of serum complement activation in the plasma of common (chelydra serpentina) and alligator (macrochelys temminckii) snapping turtles.	[this corrects the article doi: 10.1371/journal.pone.0217626.].	2019	31291346
regulation of blood flow in the pulmonary and systemic circuits during submerged swimming in common snapping turtle (chelydra serpentina).	blood flow patterns and heart rate have rarely been investigated in freely swimming turtles and their regulation during swimming is unknown. in this study, we investigated the blood flow patterns and heart rate in surfacing and during graded, submerged swimming activity in common snapping turtles. we further investigated the effects of beta-adrenergic and cholinergic receptor blockade on blood flow and heart rate during these activities. our findings illustrate that surfacing is accompanied by a ...	2019	31331940
blood flow distribution in embryonic common snapping turtles chelydra serpentina (reptilia; chelonia) during acute hypoxia and α-adrenergic regulation.	embryonic turtles have four distinct vascular beds that separately perfuse the developing embryo's body and the extra-embryonic yolk sac, amnion and chorioallantoic membrane (cam). the mechanisms enabling differential regulation of blood flow through these separate beds, in order to meet the varying demands of the embryo during development, is of current interest. the present investigation followed the changes in blood flow distribution during an acute exposure to hypoxia and after α-adrenergic ...	2019	31505219
detecting trends in body size: empirical and statistical requirements for intraspecific analyses.	attributing biological explanations to observed ecogeographical and ecological patterns require eliminating potential statistical and sampling artifacts as alternative explanations of the observed patterns. here, we assess the role of sample size, statistical power, and geographic inclusivity on the general validity and statistical significance of relationships between body size and latitude for 3 well-studied species of turtles. we extend those analyses to emphasize the importance of using stat ...	2019	31616479
further characterisation of haemocystidium chelodinae-like haemoproteidae isolated from the bellinger river snapping turtle (myuchelys georgesi).	the bellinger river snapping turtle (myuchelys georgesi) is endemic to australia and is confined to a highly restricted distribution in the bellinger river in new south wales. routine veterinary health examinations of 17 healthy turtles were undertaken, along with the collection and analysis of blood samples, during conservation efforts to save the species following a catastrophic population decline. microscopy analysis of blood films detected haemoproteidae parasites that morphologically resemb ...	2020	31754857
high prevalence of subclinical frog virus 3 infection in freshwater turtles of ontario, canada.	ranaviruses have been associated with chelonian mortality. in canada, the first two cases of ranavirus were detected in turtles in 2018 in ontario, although a subsequent survey of its prevalence failed to detect additional positive cases. to confirm the prevalence of ranavirus in turtles in ontario, we used a more sensitive method to investigate if lower level persistent infection was present in the population. here we report results via a combination of qpcr, pcr, sanger sequencing and genome s ...	2020	32174301
incubation temperature and satiety influence general locomotor and exploratory behaviors in the common snapping turtle (chelydra serpentina).	temperature during embryogenesis determines sex and has been shown to influence other physiological traits in reptiles. the common snapping turtle (chelydra serpentina) is an ideal model for testing how temperature impacts behavior in species that display temperature-dependent sex determination. behavioral assays are crucial to understanding how a changing climate may affect whole organism function in the snapping turtle. currently, there are few behavioral assays for semi-aquatic vertebrates li ...	2020	32194070
morphometric data for five freshwater turtles in south, central, and west texas.	from 2008 to 2013, we sampled freshwater turtle populations at 66 sites in south, central, and west texas, usa. sampling sites included ponds, lakes, resacas (oxbow lakes), canals, and rivers. we sampled turtle populations using baited hoop nets (66 sites) and basking traps (3 sites), and captured turtles by hand opportunistically in terrestrial habitat. we measured carapace length and width, plastron length and width, body depth, and weight of captured turtles. excluding recaptures, we measured ...	2020	32195296
wait and snap: eastern snapping turtles (chelydra serpentina) prey on migratory fish at road-stream crossing culverts.	there is growing evidence that culverts at road-stream crossings can increase fish density by reducing stream width and fish movement rates, making these passageways ideal predator ambush locations. in this study, we used a combination of videography and δ13c stable isotope analyses to investigate predator-prey interactions at a road-stream crossing culvert. eastern snapping turtles (chelydra serpentina) were found to regularly reside within the culvert to ambush migratory river herring (alosa s ...	2020	32961086
draft genome of the common snapping turtle, chelydra serpentina, a model for phenotypic plasticity in reptiles.	turtles are iconic reptiles that inhabit a range of ecosystems from oceans to deserts and climates from the tropics to northern temperate regions. yet, we have little understanding of the genetic adaptations that allow turtles to survive and reproduce in such diverse environments. common snapping turtles, chelydra serpentina, are an ideal model species for studying adaptation to climate because they are widely distributed from tropical to northern temperate zones in north america. they are also ...	2020	32998935