Publications

TitleAbstractYear
Filter
PMID(sorted ascending)
Filter
parent-offspring conflict and selection on egg size in turtles.the trade-off between offspring size and number can present a conflict between parents and their offspring. because egg size is constrained by clutch size, the optimal egg size for offspring fitness may not always be equivalent to that which maximizes parental fitness. we evaluated selection on egg size in three turtle species (apalone mutica, chelydra serpentina and chrysemys picta) to determine if optimal egg sizes differ between offspring and their mothers. although hatching success was gener ...200919796084
brief chilling to subzero temperature increases cold hardiness in the hatchling painted turtle (chrysemys picta).although many studies of ectothermic vertebrates have documented compensatory changes in cold hardiness associated with changes of season, much less attention has been paid to adjustment of physiological functions and survival limits following more acute exposure to cold. we investigated the ability of hatchling painted turtles (chrysemys picta) to increase cold hardiness in response to brief exposure to a subzero temperature. winter-acclimated turtles were "cold conditioned" by chilling them in ...201319947887
sex allocation based on relative and absolute condition.traditional models predict that organisms should allocate to sex based on their condition relative to the condition of their competitors, tracking shifts in mean condition in fluctuating environments, and maintaining an equilibrium sex ratio. in contrast, when individuals are constrained to define their condition absolutely, environmental fluctuations induce fluctuating sex ratios and the evolutionary loss of condition-dependent sex allocation in short-lived organisms. here, we present a simulat ...201020002168
inheritance of nesting behaviour across natural environmental variation in a turtle with temperature-dependent sex determination.nesting behaviour is critical for reproductive success in oviparous organisms with no parental care. in organisms where sex is determined by incubation temperature, nesting behaviour may be a prime target of selection in response to unbalanced sex ratios. to produce an evolutionary change in response to sex-ratio selection, components of nesting behaviour must be heritable. we estimated the field heritability of two key components of nesting behaviour in a population of painted turtles (chrysemy ...201020018783
multivariate expression analysis of the gene network underlying sexual development in turtle embryos with temperature-dependent and genotypic sex determination.sexual development has long been the target of study and despite great advances in our understanding of the composition and regulation of the gene network underlying gonadogenesis, our knowledge remains incomplete. of particular interest is the relative role that the environment and the genome play in directing gonadal formation, especially the effect of environmental temperature in directing this process in vertebrates. comparative analyses in closely related taxa with contrasting sex-determini ...201020110645
the painted turtle, chrysemys picta: a model system for vertebrate evolution, ecology, and human health.painted turtles (chrysemys picta) are representatives of a vertebrate clade whose biology and phylogenetic position hold a key to our understanding of fundamental aspects of vertebrate evolution. these features make them an ideal emerging model system. extensive ecological and physiological research provide the context in which to place new research advances in evolutionary genetics, genomics, evolutionary developmental biology, and ecological developmental biology which are enabled by current r ...200920147199
egg incubation and collection of painted turtle embryos.this protocol describes how to incubate painted turtle eggs and collect embryos for gene expression analysis. the same basic protocol can be used to incubate eggs and collect embryos from other turtle species by modifying the incubation temperature to suit the particular developmental needs of each species.200920147203
embryos in the fast lane: high-temperature heart rates of turtles decline after hatching.in ectotherms such as turtles, the relationship between cardiovascular function and temperature may be subject to different selective pressures in different life-history stages. because embryos benefit by developing as rapidly as possible, and can "afford" to expend energy to do so (because they have access to the yolk for nutrition), they benefit from rapid heart (and thus, developmental) rates. in contrast, hatchlings do not have a guaranteed food supply, and maximal growth rates may not enhan ...201020224773
the development of the shoulder region of the turtle, chrysemys picta marginata, with special reference to the primary musculature. 194720287830
activation of antioxidant defenses in response to freezing in freeze-tolerant painted turtle hatchlings.hatchlings of the painted turtle, chrysemys picta marginata can endure long-term freezing of their extracellular body fluids. we hypothesized that freezing survival would include adaptive up-regulation of antioxidant defenses to deal with ischemia-reperfusion injuries associated with the freeze-thaw cycle. a number of antioxidant enzymes are under the control of the nf-e2 related factor 2 (nrf2) transcription factor including members of the glutathione s-transferase (gst) and aldo-keto reductase ...201020359523
winter severity and phenology of spring emergence from the nest in freshwater turtles.although many species of freshwater turtles emigrate to water soon after hatching, the offspring of some species overwinter on land and move to aquatic habitats in the following spring. timing of emigration can affect the hatchlings' fitness, but the factors underlying phenology of nest emergence are incompletely understood. we tested the supposition that cold stress imposed during hibernation can influence the timing of nest emergence in three species of turtles in the central usa. in each year ...201020467723
physiology of hibernation under the ice by turtles and frogs.successful overwintering under ice by an air-breathing vertebrate requires either effective aquatic respiration if dissolved o(2) is available or the capacity for prolonged anaerobic metabolism if o(2) supplies are limiting. frogs can remain aerobic for many weeks when submerged at low temperature, even at water po(2) as low as 30 mmhg, but are unable to survive even 1 week in anoxic water. fuel reserves of hibernating frogs limit aerobic submergence, whereas acidosis may limit anoxic submergenc ...201020535765
regulation of ampa receptor currents by mitochondrial atp-sensitive k+ channels in anoxic turtle neurons.mammalian neurons rapidly undergo excitotoxic cell death during anoxia, whereas neurons from the anoxia-tolerant painted turtle survive without oxygen for hours and offer a unique model to study mechanisms to reduce the severity of cerebral stroke. an anoxia-mediated decrease in whole cell n-methyl-d-aspartate receptor and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (ampar) currents are an important part of the turtle's natural defense. here we investigate the role of mitochond ...201020685922
climate and predation dominate juvenile and adult recruitment in a turtle with temperature-dependent sex determination.conditions experienced early in life can influence phenotypes in ecologically important ways, as exemplified by organisms with environmental sex determination. for organisms with temperature-dependent sex determination (tsd), variation in nest temperatures induces phenotypic variation that could impact population growth rates. in environments that vary over space and time, how does this variation influence key demographic parameters (cohort sex ratio and hatchling recruitment) in early life stag ...201021058561
state-dependent physiological maintenance in a long-lived ectotherm, the painted turtle (chrysemys picta).energy allocation among somatic maintenance, reproduction and growth varies not only among species, but among individuals according to states such as age, sex and season. little research has been conducted on the somatic (physiological) maintenance of long-lived organisms, particularly ectotherms such as reptiles. in this study, we examined sex differences and age- and season-related variation in immune function and dna repair efficiency in a long-lived reptile, the painted turtle (chrysemys pic ...201121147972
effective heritability of targets of sex-ratio selection under environmental sex determination.selection is expected to maintain primary sex ratios at an evolutionary equilibrium. in organisms with temperature-dependent sex determination (tsd), targets of sex-ratio selection include the thermal sensitivity of the sex-determining pathway (hereafter, sex determination threshold) and nest-site choice. however, offspring sex may be canalized for nests located in thermally extreme environments; thus, genetic variance for the sex determination threshold is not expressed and is invisible to dire ...201121261771
hydrodynamic stability of the painted turtle (chrysemys picta): effects of four-limbed rowing versus forelimb flapping in rigid-bodied tetrapods.hydrodynamic stability is the ability to resist recoil motions of the body produced by destabilizing forces. previous studies have suggested that recoil motions can decrease locomotor performance, efficiency and sensory perception and that swimming animals might utilize kinematic strategies or possess morphological adaptations that reduce recoil motions and produce more stable trajectories. we used high-speed video to assess hydrodynamic stability during rectilinear swimming in the freshwater pa ...201121389201
the lesser known challenge of climate change: thermal variance and sex-reversal in vertebrates with temperature-dependent sex determination.climate change is expected to disrupt biological systems. particularly susceptible are species with temperature-dependent sex determination (tsd), as in many reptiles. while the potentially devastating effect of rising mean temperatures on sex ratios in tsd species is appreciated, the consequences of increased thermal variance predicted to accompany climate change remain obscure. surprisingly, no study has tested if the effect of thermal variance around high-temperatures (which are particularly ...201121448294
the ontogeny of postmaturation resource allocation in turtles.resource-allocation decisions vary with life-history strategy, and growing evidence suggests that long-lived endothermic vertebrates direct resources toward growth and self-maintenance when young, increasing allocation toward reproductive effort over time. few studies have tracked the ontogeny of resource allocation (energy, steroid hormones, etc.) in long-lived ectothermic vertebrates, limiting our understanding of the generality of life-history strategies among vertebrates. we investigated how ...201321460531
cloning of estrogen receptor alpha and aromatase cdnas and gene expression in turtles (chrysemys picta and pseudemys scripta) exposed to different environments.reproductive changes have been observed in painted turtles (chrysemys picta) from a site with known contamination located on cape cod, ma, usa. we hypothesize that these changes are caused by exposure to endocrine-disrupting compounds and that genes playing a significant role in reproduction are affected. cdna sequences were determined for estrogen receptor alpha and aromatase in the painted turtle. these genes were measured in our study animals using quantitative pcr. adult turtles were trapped ...201121664488
new resources inform study of genome size, content, and organization in nonavian reptiles.genomic resources for studies of nonavian reptiles have recently improved and will reach a new level of access once the genomes of the painted turtle (chrysemys picta) and the green anole (anolis carolinensis) have been published. eleven speakers gathered for a symposium on reptilian genomics and evolutionary genetics at the 2008 meeting of the society for integrative and comparative biology in san antonio, texas. presentations described results of reptilian genetic studies concerning molecular ...200821669805
evolution of the gene network underlying gonadogenesis in turtles with temperature-dependent and genotypic sex determination.the evolution of sex determination has long fascinated biologists, as it has paramount consequences for the evolution of a multitude of traits, from sex allocation to speciation and extinction. explaining the diversity of sex-determining systems found in vertebrates (genotypic or gsd and temperature-dependent or tsd) requires a comprehensive and integrative examination from both a functional and an evolutionary perspective. particularly revealing is the examination of the gene network that regul ...200821669808
novel cdna sequences of aryl hydrocarbon receptors and gene expression in turtles (chrysemys picta and pseudemys scripta) exposed to different environments.reproductive changes have been observed in painted turtles from a site with known contamination located on cape cod, ma, usa. we hypothesize that these changes are caused by exposure to endocrine-disrupting compounds and that genes involved in reproduction are affected. the aryl hydrocarbon receptor (ahr) is an orphan receptor that is activated by environmental contaminants. ahr mrna was measured in turtles exposed to soil collected from a contaminated site. adult turtles were trapped from the s ...201121763458
Incidental nest predation in freshwater turtles: inter- and intraspecific differences in vulnerability are explained by relative crypsis.There has long been interest in the influence of predators on prey populations, although most predator-prey studies have focused on prey species that are targets of directed predator searching. Conversely, few have addressed depredation that occurs after incidental encounters with predators. We tested two predictions stemming from the hypothesis that nest predation on two sympatric freshwater turtle species whose nests are differentially prone to opportunistic detection-painted turtles (Chrysemy ...201122009341
widespread reproductive variation in north american turtles: temperature, egg size and optimality.theory predicts the existence of an optimal offspring size that balances the trade-off between offspring fitness and offspring number. however, in wild populations of many species, egg size can still vary from year to year for unknown reasons. here, we hypothesize that among-year variation in population mean egg size of freshwater turtles is partly a consequence of their gonadal sensitivity to seasonal temperatures, a physiological mechanism which principally functions to synchronize reproductio ...201222541670
painted turtle cortex is resistant to an in vitro mimic of the ischemic mammalian penumbra.anoxia or ischemia causes hyperexcitability and cell death in mammalian neurons. conversely, in painted turtle brain anoxia increases γ-amino butyric acid (gaba)ergic suppression of spontaneous electrical activity, and cell death is prevented. to examine ischemia tolerance in turtle neurons, we treated cortical sheets with an in vitro mimic of the penumbral region of stroke-afflicted mammalian brain (ischemic solution, is). we found that during is perfusion, neuronal membrane potential (v(m)) an ...201222805876
anatomy of the fully formed chondrocranium of emydura subglobosa (chelidae): a pleurodiran turtle.the chondrocranium is a cartilaginous structure that forms around and protects the brain and sensory organs of the head. through ontogeny, this skeletal structure may become more elaborate, remodeled and reabsorbed, and/or ossified. though considerable attention has been given to the formation of the chondrocranium and a great amount of data has been gathered on the development of this structure among many craniates, the anatomy of this structure in turtles often is neglected. we describe the ma ...201322972700
transcriptional evolution underlying vertebrate sexual development.explaining the diversity of vertebrate sex-determining mechanisms ranging from genotypic (gsd) to temperature-dependent (tsd) remains a developmental and evolutionary conundrum. using a phylogenetic framework, we explore the transcriptional evolution during gonadogenesis of several genes involved in sexual development, combining novel data from chrysemys picta turtles (tsd) and published data from other tsd and gsd vertebrates. our novel c. picta dataset underscores sf1 and wt1 as potential acti ...201323108853
does maternal oviposition site influence offspring dispersal to suitable habitat?orientation and dispersal to suitable habitat affects fitness in many animals, but the factors that govern these behaviors are poorly understood. in many turtle species, hatchlings must orient and disperse to suitable aquatic habitat immediately after emergence from subterranean nests. thus, the location of nest sites relative to aquatic habitats ideally should be associated with the direction of hatchling dispersal. at our study site, painted turtles (chrysemys picta) nest to the west (on an is ...201323196739
biomechanics of turtle shells: how whole shells fail in compression.turtle shells are a form of armor that provides varying degrees of protection against predation. although this function of the shell as armor is widely appreciated, the mechanical limits of protection and the modes of failure when subjected to breaking stresses have not been well explored. we studied the mechanical properties of whole shells and of isolated bony tissues and sutures in four species of turtles (trachemys scripta, malaclemys terrapin, chrysemys picta, and terrapene carolina) using ...201323203474
immunoglobulin genes of the turtles.the availability of reptile genomes for the use of the scientific community is an exceptional opportunity to study the evolution of immunoglobulin genes. the genome of chrysemys picta bellii and pelodiscus sinensis is the first one that has been reported for turtles. the scanning for immunoglobulin genes resulted in the presence of a complex locus for the immunoglobulin heavy chain (igh). this igh locus in both turtles contains genes for 13 isotypes in c. picta bellii and 17 in p. sinensis. thes ...201323208582
molecular decay of enamel matrix protein genes in turtles and other edentulous amniotes.secondary edentulism (toothlessness) has evolved on multiple occasions in amniotes including several mammalian lineages (pangolins, anteaters, baleen whales), birds, and turtles. all edentulous amniote clades have evolved from ancestors with enamel-capped teeth. previous studies have documented the molecular decay of tooth-specific genes in edentulous mammals, all of which lost their teeth in the cenozoic, and birds, which lost their teeth in the cretaceous. by contrast with mammals and birds, t ...201323342979
oxygen-sensitive reduction in ca²⁺-activated k⁺ channel open probability in turtle cerebrocortex.in response to low ambient oxygen levels the western painted turtle brain undergoes a large depression in metabolic rate which includes a decrease in neuronal action potential frequency. this involves the arrest of n-methyl-d-aspartate receptor (nmdar) and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (ampar) currents and paradoxically an increase in γ-aminobutyric acid receptor (gabar) currents in turtle cortical neurons. in a search for other oxygen-sensitive channels we discov ...201323384611
the western painted turtle genome, a model for the evolution of extreme physiological adaptations in a slowly evolving lineage.we describe the genome of the western painted turtle, chrysemys picta bellii, one of the most widespread, abundant, and well-studied turtles. we place the genome into a comparative evolutionary context, and focus on genomic features associated with tooth loss, immune function, longevity, sex differentiation and determination, and the species' physiological capacities to withstand extreme anoxia and tissue freezing.201323537068
coelioscopic orchiectomy can be effectively and safely accomplished in chelonians.coelioscopic orchiectomy was performed in 27 male turtles (25 juvenile to adult red-eared sliders (trachemys scripta elegans), one adult eastern painted turtle (chrysems picta picta), and one juvenile male yellow-spotted amazon river turtle (podocnemis unifilis)). orchiectomy was conducted under coelioscopic visualisation using ligation and transection of the mesorchium, or transection of the mesorchium with monopolar radiosurgical scissors. in 22 cases, bilateral orchiectomy was performed throu ...201323559425
rapid evolution of beta-keratin genes contribute to phenotypic differences that distinguish turtles and birds from other reptiles.sequencing of vertebrate genomes permits changes in distinct protein families, including gene gains and losses, to be ascribed to lineage-specific phenotypes. a prominent example of this is the large-scale duplication of beta-keratin genes in the ancestors of birds, which was crucial to the subsequent evolution of their beaks, claws, and feathers. evidence suggests that the shell of pseudomys nelsoni contains at least 16 beta-keratins proteins, but it is unknown whether this is a complete set an ...201323576313
modeling the effects of climate change-induced shifts in reproductive phenology on temperature-dependent traits.by altering phenology, organisms have the potential to match life-history events with suitable environmental conditions. because of this, phenological plasticity has been proposed as a mechanism whereby populations might buffer themselves from climate change. we examine the potential buffering power of advancing one aspect of phenology, nesting date, on sex ratio in painted turtles (chrysemys picta), a species with temperature-dependent sex determination. we developed a modified constant tempera ...201323594547
phenotypic and fitness consequences of maternal nest-site choice across multiple early life stages.identifying the relative contributions of genetic, maternal, and environmental factors to phenotypic variation is critical for evaluating the evolutionary potential of fitness-related traits. we employed a novel two-step cross-fostering experiment to quantify the relative contributions of clutch (i.e., maternal identity) and maternally chosen nest sites to phenotypic variation during three early life stages (incubation, hibernation, dispersal) of the painted turtle (chrysemys picta). by transloc ...201323691653
extreme developmental temperatures result in morphological abnormalities in painted turtles (chrysemys picta): a climate change perspective.increases in extreme environmental events are predicted to be major results of ongoing global climate change and may impact the persistence of species. we examined the effects of heat and cold waves during embryonic development of painted turtles (chrysemys picta) in natural nests on the occurrence of abnormal shell morphologies in hatchlings. we found that nests exposed to extreme hot temperatures for >60 h produced more hatchlings with abnormalities than nests exposed to extreme hot temperatur ...201323731815
cytoplasmic droplets of painted turtle spermatozoa.epididymal sperm from the painted turtle (chrysemys picta) possess a cytoplasmic droplet which is located eccentrically on the sperm midpiece. the droplet contains a large quantity of lipid droplets in addition to hollow vesicles and degenerate mitochondrial fragments. lipid droplets are closely associated with mitochondrial membranes and may function in the formation or degradation of mitochondria. cytoplasmic droplets become detached from the sperm midpiece in a coordinated manner shortly befo ...199223865099
hepatic biotransformation enzymes in a sentinel species, the painted turtle (chrysemys picta), from cape cod, massachusetts: seasonal-, sex- and location related differences.we report changes in biomarker enzymes (cytochrome p4501a, glutathione-s-transferase) and protein expression (cytochrome p4501a) in adult painted turtles, chrysemys picta, as part of a study of the potential impact of contaminants originating from the massachusetts military reservation on cape, cod, ma. in animals from both moody pond, a site potentially impacted by contaminants, and washburn pond, a nonimpacted site, rates of hepatic microsomal ethoxyresorufin-o.200023886024
taking the temperature of the painted turtle. 201323965557
anoxia-mediated calcium release through the mitochondrial permeability transition pore silences nmda receptor currents in turtle neurons.mammalian neurons are anoxia sensitive and rapidly undergo excitotoxic cell death when deprived of oxygen, mediated largely by ca(2+) entry through over-activation of n-methyl-d-aspartate receptors (nmdars). this does not occur in neurons of the anoxia-tolerant western painted turtle, where a decrease in nmdar currents is observed with anoxia. this decrease is dependent on a modest rise in cytosolic [ca(2+)] ([ca(2+)]c) that is mediated by release from the mitochondria. the aim of this study was ...201324259257
does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. for reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by cho ...201324266033
an enhanced developmental staging table for the painted turtle, chrysemys picta (testudines: emydidae).normal developmental staging tables often undergo expansion and enhancement in response to advancing research paradigms and technologies. the painted turtle, chrysemys picta, has long been a preferred reference taxon for comparative embryology and recently became the first turtle species to feature a sequenced genome. however, modern descriptive studies on embryogenesis are lacking and an earlier developmental staging table has been ignored. to address these problems, we re-evaluated description ...201424301536
the complete mitochondrial genome of western painted turtle, chrysemys picta bellii (chrysemys, emydidae).in this study, we report the complete mitochondrial genome sequence of western painted turtle, chrysemys picta bellii. the genome is found to be 16,875 bp in length and has a base composition of a (34.4%), g (13.0%), c (26.0%), and t (26.6%). similar to other turtles, it contains a typically conserved structure including 13 protein-coding genes, 22 transfer rna genes, 2 ribosomal rna genes, and 1 control region (d-loop). most of the genes are encoded on h-strand, except for the eight trna and nd ...201624438258
daily and annual patterns of thermoregulation in painted turtles (chrysemys picta marginata) living in a thermally variable marsh in northern michigan.the capacity for an ectothermic reptile to thermoregulate has implications for many components of its life history. over two years, we studied thermoregulation in a population of midland painted turtles (chrysemys picta marginata) in a shallow, thermally variable wetland during summer in northern michigan. mean body temperature (tb) of free-ranging turtles was greater in 2008 (25.8 °c) than in 2010 (19.7 °c). laboratory determined thermoregulatory set point (tset) ranged from 25 °c (tset-min) to ...201424556255
swimming against the tide: resilience of a riverine turtle to recurrent extreme environmental events.extreme environmental events (eees) are likely to exert deleterious effects on populations. from 1996 to 2012 we studied the nesting dynamics of a riverine population of painted turtles (chrysemys picta) that experienced seven years with significantly definable spring floods. we used capture-mark-recapture methods to estimate the relationships between more than 5 m and more than 6 m flood events and population parameters. contrary to expectations, flooding was not associated with annual differen ...201424621555
experimental feeding of hydrilla verticillata colonized by stigonematales cyanobacteria induces vacuolar myelinopathy in painted turtles (chrysemys picta).vacuolar myelinopathy (vm) is a neurologic disease primarily found in birds that occurs when wildlife ingest submerged aquatic vegetation colonized by an uncharacterized toxin-producing cyanobacterium (hereafter "ucb" for "uncharacterized cyanobacterium"). turtles are among the closest extant relatives of birds and many species directly and/or indirectly consume aquatic vegetation. however, it is unknown whether turtles can develop vm. we conducted a feeding trial to determine whether painted tu ...201424695109
mapping species distributions with maxent using a geographically biased sample of presence data: a performance assessment of methods for correcting sampling bias.maxent is now a common species distribution modeling (sdm) tool used by conservation practitioners for predicting the distribution of a species from a set of records and environmental predictors. however, datasets of species occurrence used to train the model are often biased in the geographical space because of unequal sampling effort across the study area. this bias may be a source of strong inaccuracy in the resulting model and could lead to incorrect predictions. although a number of samplin ...201424818607
do roads reduce painted turtle (chrysemys picta) populations?road mortality is thought to be a leading cause of turtle population decline. however, empirical evidence of the direct negative effects of road mortality on turtle population abundance is lacking. the purpose of this study was to provide a strong test of the prediction that roads reduce turtle population abundance. while controlling for potentially confounding variables, we compared relative abundance of painted turtles (chrysemys picta) in 20 ponds in eastern ontario, 10 as close as possible t ...201424858065
exogenous application of estradiol to eggs unexpectedly induces male development in two turtle species with temperature-dependent sex determination.steroid hormones affect sex determination in a variety of vertebrates. the feminizing effects of exposure to estradiol and the masculinizing effects of aromatase inhibition during development are well established in a broad range of vertebrate taxa, but paradoxical findings are occasionally reported. four independent experiments were conducted on two turtle species with temperature-dependent sex determination (chrysemys picta and chelydra serpentina) to quantify the effects of egg incubation tem ...201424954686
re-emergence of the painted turtle (chrysemys picta) as a reference species for evo-devo.evolutionary developmental biology requires integration of knowledge from multiple levels of organization. information at the genome level is quickly outpacing crucial descriptive information on developmental processes at the cell, tissue, and organ levels. unprecedented progress in genomics has enabled the rise of so-called non-traditional reference species. however, a substantial, though overlooked, amount of phenotypic information has long been available for species such as the painted turtle ...201424980987
a novel hypothesis for the adaptive maintenance of environmental sex determination in a turtle.temperature-dependent sex determination (tsd) is widespread in reptiles, yet its adaptive significance and mechanisms for its maintenance remain obscure and controversial. comparative analyses identify an ancient origin of tsd in turtles, crocodiles and tuatara, suggesting that this trait should be advantageous in order to persist. based on this assumption, researchers primarily, and with minimal success, have employed a model to examine sex-specific variation in hatchling phenotypes and fitness ...201425009063
scavenging ros dramatically increase nmda receptor whole-cell currents in painted turtle cortical neurons.oxygen deprivation triggers excitotoxic cell death in mammal neurons through excessive calcium loading via over-activation of n-methyl-d-aspartate (nmda) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (ampa) receptors. this does not occur in the western painted turtle, which overwinters for months without oxygen. neurological damage is avoided through anoxia-mediated decreases in nmda and ampa receptor currents that are dependent upon a modest rise in intracellular ca(2+) concentra ...201425063855
molecular cytogenetic search for cryptic sex chromosomes in painted turtles chrysemys picta.sex determination is triggered by factors ranging from genotypic (gsd) to environmental (esd), or both gsd + ee (gsd susceptible to environmental effects), and its evolution remains enigmatic. the presence/absence of sex chromosomes purportedly separates species at the esd end of the continuum from the rest (gsd and gsd + ee) because the evolutionary dynamics of sex chromosomes and autosomes differ. however, studies suggest that turtles with temperature-dependent sex determination (tsd) are cryp ...201425170556
potential sources of intra-population variation in the overwintering strategy of painted turtle (chrysemys picta) hatchlings.many temperate animals spend half their lives in a non-active, overwintering state, and multiple adaptations have evolved to enable winter survival. one notable vertebrate model is chrysemys picta, whose hatchlings display dichotomous overwintering strategies: some hatchlings spend their first winter aquatically after nest emergence in the autumn, whereas others overwinter terrestrially within their natal nest with subsequent emergence in the spring. the occurrence of these strategies varies amo ...201425324341
evolution of an expanded mannose receptor gene family.sequences of peptides from a protein specifically immunoprecipitated by an antibody, kul01, that recognises chicken macrophages, identified a homologue of the mammalian mannose receptor, mrc1, which we called mrc1l-b. inspection of the genomic environment of the chicken gene revealed an array of five paralogous genes, mrc1l-a to mrc1l-e, located between conserved flanking genes found either side of the single mrc1 gene in mammals. transcripts of all five genes were detected in rna from a macroph ...201425390371
the role of age-specific learning and experience for turtles navigating a changing landscape.the severity of the environment often influences animal cognition [1-6], as does the rate of change within that environment [7-10]. rapid alteration of habitat places limitations on basic resources such as energy, water, nesting sites, and refugia [8, 10]. how animals respond to these situations provides insight into the mechanisms of cognition and the role of behavior in adaptation [11-13]. we tested the hypothesis that learning plays a role in the navigation of the painted turtle (chrysemys pi ...201525578905
proteomic changes in the brain of the western painted turtle (chrysemys picta bellii) during exposure to anoxia.during anoxia, overall protein synthesis is almost undetectable in the brain of the western painted turtle. the aim of this investigation was to address the question of whether there are alterations to specific proteins by comparing the normoxic and anoxic brain proteomes. reductions in creatine kinase, hexokinase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase reflected the reduced production of adenosine triphosphate (atp) during anoxia while the reduction in transitional endopl ...201525583675
underwater turning movement during foraging in hydromedusa maximiliani (testudines, chelidae) from southeastern brazil.a type of locomotor behavior observed in animals with rigid bodies, that can be found in many animals with exoskeletons, shells, or other forms of body armor, to change direction, is the turning behavior. aquatic floated-turning behavior among rigid bodies animals have been studied in whirligig beetles, boxfish, and more recently in freshwater turtle, chrysemys picta. in the laboratory we observed a different kind of turning movement that consists in an underwater turning movement during foragin ...201425627611
effects of a novel climate on stress response and immune function in painted turtles (chrysemys picta).climate change may subject animals to increasingly stressful environmental conditions, which could have negative physiological consequences if stress levels are elevated for long periods. we conducted a manipulative experiment to determine the effects of a novel climate on stress levels and immune function in a model reptile species, the painted turtle. we collected turtles from four populations across the species' geographic range and housed them in a common-garden in one population's local cli ...201525676021
hypoxia tolerance, nitric oxide, and nitrite: lessons from extreme animals.among vertebrates able to tolerate periods of oxygen deprivation, the painted and red-eared slider turtles (chrysemys picta and trachemys scripta) and the crucian carp (carassius carassius) are the most extreme and can survive even months of total lack of oxygen during winter. the key to hypoxia survival resides in concerted physiological responses, including strong metabolic depression, protection against oxidative damage and-in air-breathing animals-redistribution of blood flow. each of these ...201525729057
tissue hypoxia during ischemic stroke: adaptive clues from hypoxia-tolerant animal models.the treatment and prevention of hypoxic/ischemic brain injury in stroke patients remain a severe and global medical issue. numerous clinical studies have resulted in a failure to develop chemical neuroprotection for acute, ischemic stroke. over 150 estimated clinical trials of ischemic stroke treatments have been done, and more than 200 drugs and combinations of drugs for ischemic and hemorrhagic strokes have been developed. billions of dollars have been invested for new scientific breakthroughs ...201525738761
decreases in mitochondrial reactive oxygen species initiate gaba(a) receptor-mediated electrical suppression in anoxia-tolerant turtle neurons.anoxia induces hyper-excitability and cell death in mammalian brain but in the anoxia-tolerant western painted turtle (chrysemys picta bellii) neuronal electrical activity is suppressed (i.e. spike arrest), adenosine triphosphate (atp) consumption is reduced, and cell death does not occur. electrical suppression is primarily the result of enhanced γ-aminobutyric acid (gaba) transmission; however, the underlying mechanism responsible for initiating oxygen-sensitive gabaergic spike arrest is unkno ...201525781154
developmental exposure to bisphenol a (bpa) alters sexual differentiation in painted turtles (chrysemys picta).environmental chemicals can disrupt endocrine signaling and adversely impact sexual differentiation in wildlife. bisphenol a (bpa) is an estrogenic chemical commonly found in a variety of habitats. in this study, we used painted turtles (chrysemys picta), which have temperature-dependent sex determination (tsd), as an animal model for ontogenetic endocrine disruption by bpa. we hypothesized that bpa would override tsd and disrupt sexual development. we incubated farm-raised turtle eggs at the ma ...201525863134
emydid herpesvirus 1 infection in northern map turtles (graptemys geographica) and painted turtles (chrysemys picta).a captive, juvenile, female northern map turtle (graptemys geographica) was found dead following a brief period of weakness and nasal discharge. postmortem examination identified pneumonia with necrosis and numerous epithelial, intranuclear viral inclusion bodies, consistent with herpesviral pneumonia. similar intranuclear inclusions were also associated with foci of hepatocellular and splenic necrosis. polymerase chain reaction (pcr) screening of fresh, frozen liver for the herpesviral dna-depe ...201525943128
rethinking biogeographic patterns: high local variation in relation to latitudinal clines for a widely distributed species.wide-ranging species typically differ morphologically across their ranges. bergmann's rule suggests that taxa in colder environments are bigger than related taxa in warmer locations. we examined 767 painted turtles (chrysemys picta) in ten populations near their northwestern range edge in south-central british columbia, canada, in conjunction with previous data, to test the hypotheses of (1) a bergmann's latitudinal cline, and (2) that males and females show similar latitudinal variation in size ...201525975206
comparative analysis of glucagonergic cells, glia, and the circumferential marginal zone in the reptilian retina.retinal progenitors in the circumferential marginal zone (cmz) and müller glia-derived progenitors have been well described for the eyes of fish, amphibians, and birds. however, there is no information regarding a cmz and the nature of retinal glia in species phylogenetically bridging amphibians and birds. the purpose of this study was to examine the retinal glia and investigate whether a cmz is present in the eyes of reptilian species. we used immunohistochemical analyses to study retinal glia, ...201626053997
the full globin repertoire of turtles provides insights into vertebrate globin evolution and functions.globins are small heme proteins that play an important role in oxygen supply, but may also have other functions. globins offer a unique opportunity to study the functional evolution of genes and proteins. we have characterized the globin repertoire of two different turtle species: the chinese softshell turtle (pelodiscus sinensis) and the western painted turtle (chrysemys picta bellii). in the genomes of both species, we have identified eight distinct globin types: hemoglobin (hb), myoglobin, ne ...201526078264
physical mapping and refinement of the painted turtle genome (chrysemys picta) inform amniote genome evolution and challenge turtle-bird chromosomal conservation.comparative genomics continues illuminating amniote genome evolution, but for many lineages our understanding remains incomplete. here, we refine the assembly (cpi 3.0.3 ncbi ahgy00000000.2) and develop a cytogenetic map of the painted turtle (chrysemys picta-cpi) genome, the first in turtles and in vertebrates with temperature-dependent sex determination. a comparison of turtle genomes with those of chicken, selected nonavian reptiles, and human revealed shared and novel genomic features, such ...201526108489
transcriptomic responses of the heart and brain to anoxia in the western painted turtle.painted turtles are the most anoxia-tolerant tetrapods known, capable of surviving without oxygen for more than four months at 3°c and 30 hours at 20°c. to investigate the transcriptomic basis of this ability, we used rna-seq to quantify mrna expression in the painted turtle ventricle and telencephalon after 24 hours of anoxia at 19°c. reads were obtained from 22,174 different genes, 13,236 of which were compared statistically between treatments for each tissue. total tissue rna contents decreas ...201526147940
molecular characterization, tissue expression profile and snp analysis of porcine glp2r.glucagon-like peptide-2 receptor (glp2r), a member of the g-protein-coupled receptor family, plays an important role in intramuscular fat formation. little is known, however, about porcine glp2r. in the present study, glp2r was cloned, and its expression in pig muscle characterized. by rapid amplification of cdna ends, gene sequence was obtained from shaziling pigs. full-length cdna was 1868 bp, including an open reading frame 1665 bp in length, encoding 554 amino acids, and 203 bp at the 3' end ...201526505446
low-temperature microrna expression in the painted turtle, chrysemys picta during freezing stress.natural freeze tolerance depends on cellular adaptations that address the multiple stresses imposed on cells during freezing. these adaptations preserve viability by suppressing energy-expensive cell processes in the frozen state. in this study, we explore the freeze-responsive expression of microrna in hatchling painted turtles exposed to 20 h freezing. furthermore, we also explore the possibility of unique temperature-sensitive microrna targeting programs that aid in adapting turtles for survi ...201526519560
comparative genomics identifies epidermal proteins associated with the evolution of the turtle shell.the evolution of reptiles, birds, and mammals was associated with the origin of unique integumentary structures. studies on lizards, chicken, and humans have suggested that the evolution of major structural proteins of the outermost, cornified layers of the epidermis was driven by the diversification of a gene cluster called epidermal differentiation complex (edc). turtles have evolved unique defense mechanisms that depend on mechanically resilient modifications of the epidermis. to investigate ...201626601937
body burdens of heavy metals in lake michigan wetland turtles.tissue heavy metal concentrations in painted (chrysemys picta) and snapping (chelydra serpentina) turtles from lake michigan coastal wetlands were analyzed to determine (1) whether turtles accumulated heavy metals, (2) if tissue metal concentrations were related to environmental metal concentrations, and (3) the potential for non-lethal sampling techniques to be used for monitoring heavy metal body burdens in freshwater turtles. muscle, liver, shell, and claw samples were collected from painted ...201626832725
discovery of the youngest sex chromosomes reveals first case of convergent co-option of ancestral autosomes in turtles.most turtle species possess temperature-dependent sex determination (tsd), but genotypic sex determination (gsd) has evolved multiple times independently from the tsd ancestral condition. gsd in animals typically involves sex chromosomes, yet the sex chromosome system of only 9 out of 18 known gsd turtles has been characterized. here, we combine comparative genome hybridization (cgh) and bac clone fluorescent in situ hybridization (bac fish) to identify a macro-chromosome xx/xy system in the gsd ...201726842819
pharmacological evidence is consistent with a prominent role of spatial memory in complex navigation.the ability to learn about the spatial environment plays an important role in navigation, migration, dispersal, and foraging. however, our understanding of both the role of cognition in the development of navigation strategies and the mechanisms underlying these strategies is limited. we tested the hypothesis that complex navigation is facilitated by spatial memory in a population of chrysemys picta that navigate with extreme precision (±3.5 m) using specific routes that must be learned prior to ...201626865305
turtles outsmart rapid environmental change: the role of cognition in navigation.animals inhabiting changing environments show high levels of cognitive plasticity. cognition may be a means by which animals buffer the impact of environmental change. however, studies examining the evolution of cognition seldom compare populations where change is rapid and selection pressures are strong. we investigated this phenomenon by radiotracking experienced and naïve eastern painted turtles (chrysemys picta) as they sought new habitats when their pond was drained. resident adults repeate ...201727065017
effects of low-oxygen conditions on embryo growth in the painted turtle, chrysemys picta.low-oxygen conditions (hypoxia; <21% o2 ) are considered unfavorable for growth; yet, embryos of many vertebrate taxa develop successfully in hypoxic subterranean environments. although enhanced tolerance to hypoxia has been demonstrated in adult reptiles, such as in the painted turtle (chrysemys picta), its effects on sensitive embryo life stages warrant attention. we tested the hypothesis that short-term hypoxia negatively affects growth during day 40 of development in c. picta, when o2 demand ...201727135638
decades of field data reveal that turtles senesce in the wild.lifespan and aging rates vary considerably across taxa; thus, understanding the factors that lead to this variation is a primary goal in biology and has ramifications for understanding constraints and flexibility in human aging. theory predicts that senescence-declining reproduction and increasing mortality with advancing age-evolves when selection against harmful mutations is weaker at old ages relative to young ages or when selection favors pleiotropic alleles with beneficial effects early in ...201627140634
postembryonic nephrogenesis and persistence of six2-expressing nephron progenitor cells in the reptilian kidney.new nephron formation (nephrogenesis) ceases in mammals around birth and is completely absent in adults. in contrast, postembryonic nephrogenesis is well documented in the mesonephric kidneys of fishes and amphibians. the transient mesonephros in reptiles (including birds) and mammals is replaced by the metanephros during embryogenesis. thus, one may speculate that postembryonic nephrogenesis is restricted to the mesonephric kidney. previous reports have suggested the metanephros of non-avian re ...201627144443
phosphorylation of the mitochondrial atp-sensitive potassium channel occurs independently of pkcε in turtle brain.neurons from the western painted turtle (chrysemys picta bellii) are remarkably resilient to anoxia. this is partly due to a reduction in the permeability of excitatory glutamatergic ion channels, initiated by mitochondrial atp-sensitive k(+) (mk(+)atp) channel activation. the aim of this study was to determine if: 1) pkcε, a kinase associated with hypoxic stress tolerance, is more highly expressed in turtle brain than the anoxia-intolerant rat brain; 2) pkcε translocates to the mitochondrial me ...201627280321
a novel technique to measure chronic levels of corticosterone in turtles living around a major roadway.conservation biology integrates multiple disciplines to expand the ability to identify threats to populations and develop mitigation for these threats. road ecology is a branch of conservation biology that examines interactions between wildlife and roadways. although the direct threats of road mortality and habitat fragmentation posed by roads have received much attention, a clear understanding of the indirect physiological effects of roads on wildlife is lacking. chronic physiological stress ca ...201427293657
stress hormone levels in a freshwater turtle from sites differing in human activity.glucocorticoids, such as corticosterone (cort), commonly serve as a measure of stress levels in vertebrate populations. these hormones have been implicated in regulation of feeding behaviour, locomotor activity, body mass, lipid metabolism and other crucial behaviours and physiological processes. thus, understanding how glucocorticoids fluctuate seasonally and in response to specific stressors can yield insight into organismal health and the overall health of populations. i compared circulating ...201627293763
the metabolic consequences of repeated anoxic stress in the western painted turtle, chrysemys picta bellii.the painted turtle is known for its extreme tolerance to anoxia, but it is unknown whether previous experience with anoxic stress might alter physiological performance during or following a test bout of anoxia. repeatedly subjecting 25°c-acclimated painted turtles to 2h of anoxic stress every other day for 19days (10 submergence bouts total) caused resting levels of liver glycogen to decrease by 17% and liver citrate synthase (cs) and cytochrome oxidase (cox) activities to increase by 33% and 11 ...201727474083
effects of developmental exposure to bisphenol a and ethinyl estradiol on spatial navigational learning and memory in painted turtles (chrysemys picta).developmental exposure of turtles and other reptiles to endocrine disrupting chemicals (edcs), including bisphenol a (bpa) and ethinyl estradiol (ee2, estrogen present in birth control pills), can induce partial to full gonadal sex-reversal in males. no prior studies have considered whether in ovo exposure to edcs disrupts normal brain sexual differentiation. yet, rodent model studies indicate early exposure to these chemicals disturbs sexually selected behavioral traits, including spatial navig ...201627476434
assessment of anoxia tolerance and photoperiod dependence of gabaergic polarity in the pond snail lymnaea stagnalis.the pond snail lymnaea stagnalis is reported to be anoxia-tolerant and if the tolerance mechanism is similar to that of the anoxia-tolerant painted turtle, gaba should play an important role. a potentially confounding factor investigating the role of gaba in anoxia tolerance are reports that gaba has both inhibitory and excitatory effects within l. stagnalis central ganglion. we therefore set out to determine if seasonality or photoperiod has an impact on: 1) the anoxia-tolerance of the intact p ...201727664385
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
using pharmacological manipulation and high-precision radio telemetry to study the spatial cognition in free-ranging animals.an animal's ability to perceive and learn about its environment plays a key role in many behavioral processes, including navigation, migration, dispersal and foraging. however, the understanding of the role of cognition in the development of navigation strategies and the mechanisms underlying these strategies is limited by the methodological difficulties involved in monitoring, manipulating the cognition of, and tracking wild animals. this study describes a protocol for addressing the role of co ...201627842346
phenotypic plasticity of nest timing in a post-glacial landscape: how do reptiles adapt to seasonal time constraints?life histories evolve in response to constraints on the time available for growth and development. nesting date and its plasticity in response to spring temperature may therefore be important components of fitness in oviparous ectotherms near their northern range limit, as reproducing early provides more time for embryos to complete development before winter. we used data collected over several decades to compare air temperature and nest date plasticity in populations of painted turtles and snap ...201727870008
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
one foot out the door: limb function during swimming in terrestrial versus aquatic turtles.specialization for a new habitat often entails a cost to performance in the ancestral habitat. although aquatic lifestyles are ancestral among extant cryptodiran turtles, multiple lineages, including tortoises (testudinidae) and emydid box turtles (genus terrapene), independently specialized for terrestrial habitats. to what extent is swimming function retained in such lineages despite terrestrial specialization? because tortoises diverged from other turtles over 50 ma, but box turtles did so on ...201728123109
transcriptomic alterations in the brain of painted turtles (chrysemys picta) developmentally exposed to bisphenol a or ethinyl estradiol.developmental exposure of turtles and other reptiles to endocrine-disrupting chemicals (edcs), including bisphenol a (bpa) and ethinyl estradiol (ee), can stimulate partial to full gonadal sex-reversal in males. we have also recently shown that in ovo exposure to either edc can induce similar sex-dependent behavioral changes typified by improved spatial learning and memory or possibly feminized brain responses. observed behavioral changes are presumed to be due to bpa- and ee-induced brain trans ...201728159858
transcriptomic responses to environmental temperature by turtles with temperature-dependent and genotypic sex determination assessed by rnaseq inform the genetic architecture of embryonic gonadal development.vertebrate sexual fate is decided primarily by the individual's genotype (gsd), by the environmental temperature during development (tsd), or both. turtles exhibit tsd and gsd, making them ideal to study the evolution of sex determination. here we analyze temperature-specific gonadal transcriptomes (rna-sequencing validated by qpcr) of painted turtles (chrysemys picta tsd) before and during the thermosensitive period, and at equivalent stages in soft-shell turtles (apalone spinifera-gsd), to tes ...201728296881
characterization of melanin-concentrating hormone (mch) and its receptor in chickens: tissue expression, functional analysis, and fasting-induced up-regulation of hypothalamic mch expression.melanin-concentrating hormone (mch) is a neuropeptide expressed in the brain and exerts its actions through interaction with the two known g protein-coupled receptors, namely melanin-concentrating hormone receptor 1 and 2 (mchr1 and mchr2) in mammals. however, the information regarding the expression and functionality of mch and mchr(s) remains largely unknown in birds. in this study, using rt-pcr and race pcr, we amplified and cloned a mchr1-like receptor, which is named cmchr4 according to its ...201728300612
reproductive variation and the egg size-clutch size trade-off within and among populations of painted turtles (chrysemys picta bellii).interpopulation variation in egg size, clutch size and clutch mass was studied 3 years in four populations of painted turtles (chrysemys picta bellii) from western nebraska. body size varied among all populations and was larger in two large (56-110 ha), sandhills lake populations than in two populations in smaller habitats (1.5-3.6 ha) of the platte river floodplain. reproductive parameters (egg mass, clutch mass, and clutch size) generally increased with maternal body size within populations. c ...199428313946
demonstrating the value and importance of combining dna barcodes and discriminant morphological characters for polystome taxonomy (platyhelminthes, monogenea).polystomes are monogenean parasites that infest mainly semi aquatic vertebrates, such as amphibians and chelonians. owing to the lack of discriminative morphological characters and because polystomes are considered to be strictly host- and site-specific, host identity is often used as an additional character for parasite identification. recent genetic studies, however, showed that polystomes infecting freshwater turtles in outdoor turtle enclosures and natural environments, were not strictly hos ...201728336417
daily thermal fluctuations to a range of subzero temperatures enhance cold hardiness of winter-acclimated turtles.although seasonal increases in cold hardiness are well documented for temperate and polar ectotherms, relatively little is known about supplemental increases in cold hardiness during winter. because many animals are exposed to considerable thermal variation in winter, they may benefit from a quick enhancement of cold tolerance prior to extreme low temperature. hatchling painted turtles (chrysemys picta) overwintering in their natal nests experience substantial thermal variation in winter, and re ...201728409226
genetic polymorphisms in aromatase (cyp19a1) are not associated with gonadal phenotypes in red-eared slider turtle hatchlings developed at a pivotal temperature.embryonic gonad sex in many reptilian species is determined by the incubation temperature of the egg, a differentiation process known as temperature-dependent sex determination (tsd). incubation at the pivotal temperature (pvt) results in approximately an equal number of offspring of both sexes. we investigated the potential contribution of genetic variations that drives the gonadal differentiation into testes or ovaries under this temperature in the red-eared slider turtle (trachemys scripta). ...201728445889
Refresh
firstprev
12345
nextlast
Displaying items 301 - 400 of 445