Publications

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diatoms on the carapace of common snapping turtles: luticola spp. dominate despite spatial variation in assemblages.filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. compared to filamentous algae, little is known about the much more speciose microalgae on turtles. our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, chelydra serpentina) across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently a ...201728192469
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
genetic effects of landscape, habitat preference and demography on three co-occurring turtle species.expanding the scope of landscape genetics beyond the level of single species can help to reveal how species traits influence responses to environmental change. multispecies studies are particularly valuable in highly threatened taxa, such as turtles, in which the impacts of anthropogenic change are strongly influenced by interspecific differences in life history strategies, habitat preferences and mobility. we sampled approximately 1500 individuals of three co-occurring turtle species across a g ...201727997082
ontogenetic shifts in the diet of plains hog-nosed snakes (heterodon nasicus) revealed by stable isotope analysis.wild snake diets are difficult to study using traditional methods, but stable isotopes offer several advantages, including integrating dietary information over time, providing data from individuals that have not fed recently, and avoiding bias towards slowly-digesting prey items. we used stable isotope signatures of carbon and nitrogen from scale tissue, red blood cells, and blood plasma to assess the diet of wild plains hog-nosed snakes (heterodon nasicus) in illinois. we developed bayesian mix ...201727692795
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 ...201829962084
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 ...201830356240
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 ...201830592915
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 ...201830568851
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 ...201830065037
a new method of estimating thermal performance of embryonic development rate yields accurate prediction of embryonic age in wild reptile nests.temperature has a strong effect on ectotherm development rate. it is therefore possible to construct predictive models of development that rely solely on temperature, which have applications in a range of biological fields. here, we leverage a reference series of development stages for embryos of the turtle chelydra serpentina, which was described at a constant temperature of 20 °c. the reference series acts to map each distinct developmental stage onto embryonic age (in days) at 20 °c. by exten ...201829801626
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 ...201830123718
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 ...201830073403
assessment of blood lead, zinc, and mercury concentrations and cholinesterase activity in captive-reared alligator snapping turtles ( macrochelys temminckii) in louisiana, usa.the alligator snapping turtle ( macrochelys temminckii) is a freshwater apex predator that has experienced severe population declines throughout its range due to historical overharvesting and habitat degradation. because of its long lifespan, high trophic level, and limited home range, it is a suitable sentinel species for monitoring environmental contaminants. in louisiana, us a pilot program aims to augment free-ranging populations by releasing captive-reared individuals. baseline values of po ...201829697311
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 ...201930352829
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 ...201930081360
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 ...201930273972
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 ...201930268769
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 ...201931238852
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 ...201931188138
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 ...201931616479
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 ...201930809267
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 ...201931505219
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 ...201931331940
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.].201931291346
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 ...201930226800
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 ...201931170203
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 ...201931120665
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 ...201931059691
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 ...201931004807
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 ...201930953168
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 ...202032194070
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 ...202032174301
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 ...202032998935
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 ...202031754857
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 ...202032961086
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 ...202032195296
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