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Environmental conditions vary greatly across large geographic ranges, and yet certain species inhabit entire continents. In such species, genomic sequencing can inform our understanding of colonization history and the impact of selection on the genome as populations experience diverse local environments. As ectothermic vertebrates are among the most vulnerable to environmental change, it is critical to understand the contributions of local adaptation to population survival. Widespread ectotherms offer an opportunity to explore how species can successfully inhabit such differing environments and how future climatic shifts will impact species' survival. In this study, we investigated the widespread painted turtle (Chrysemys picta) to assess population genomic structure, demographic history, and genomic signatures of selection in the western extent of the range. We found support for a substantial role of serial founder effects in shaping population genomic structure: demographic analysis and runs of homozygosity were consistent with bottlenecks of increasing severity from eastern to western populations during and following the Last Glacial Maximum, and edge populations were more strongly diverged and had less genetic diversity than those from the centre of the range. We also detected outlier loci, but allelic patterns in many loci could be explained by either genetic surfing or selection. While range expansion complicates the identification of loci under selection, we provide candidates for future study of local adaptation in a long‐lived, widespread ectotherm that faces an uncertain future as the global climate continues to rapidly change. [ABSTRACT FROM AUTHOR]

Turtles often present to wildlife rehabilitation centers for trauma secondary to motor vehicle collisions. Injuries to the pelvic girdles in turtles are challenging to assess on standard radiographic views due to the superimposition of bones. Pelvic trauma may have long-term consequences for ambulation and reproduction. The novel use of caudoventral-craniodorsal and cranioventral-caudodorsal 45° oblique radiographic views in western painted turtles (Chrysemys picta bellii) at the Wildlife Rehabilitation Center of Minnesota has improved differentiation of bones in the pelvic girdle. Using dorsoventral radiographs, 45% of western painted turtles with caudal carapace fractures had suspected injuries to the pelvis. After using oblique views, 98% of western painted turtles with caudal carapace fractures were found to have pelvic involvement. These radiographic views improve diagnostic ability, facilitate medical and surgical interventions, and aid in monitoring the healing process. [ABSTRACT FROM AUTHOR]

The demography of a painted turtle Chrysemys picta picta X C. p. marginata population from a eutrophic habitat was examined at a wetland site in south-central Pennsylvania (USA) during 2011-2019. Males reached sexual maturity at 90 mm carapace length (CL) in half the time taken, but at the same size, as painted turtles studied elsewhere in the north-eastern portion of the United States. Females matured at 130 mm CL at our site, which was larger and began at an earlier age than conspecifics. Our data corroborate findings of faster growth in C. picta juveniles resulting in earlier maturity at body sizes equal to or larger than slower growing juveniles. Our results also conform to previous findings linking wetlands altered by added nutrient input to increased growth patterns of their resident painted turtle population. Rapid growth rates for aquatic turtles are likely to become more common globally as urbanisation continues to expand and alter wetland habitats. [ABSTRACT FROM AUTHOR]

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Between 2011 and 2020, the Ontario Turtle Conservation Centre's veterinary hospital admitted 6,335 turtles of eight different species, with 3,246 being midland painted turtles (Chrysemys picta marginata). At the time of admission from the wild, aural abscesses were present in 26 of the painted turtles (0.8%). Aural abscesses were never observed in juvenile turtles and were not found in any other species of turtle admitted to the hospital. An equal number of males and females were affected. All cases showed signs of chronicity. Abscesses alone did not appear to affect the overall health of turtles regardless of clinical signs. All turtles with abscesses as the sole cause for admission were released after successful treatment. [ABSTRACT FROM AUTHOR]

Many species consider both prior experiences and the context of current stimuli when making behavioural decisions. Herein, we explore the influence of prior experience and novel incoming stimuli on the decision-making in the Eastern painted turtle (Chrysemys picta). We used a free-choice Y-maze to assess the preferences of turtles wavelength and intensity of light. We then trained naïve turtles to associate one arm of a maze with a food reward, and then tested the relevance of light colour and intensity on the turtles' decision-making regarding arm choice. Turtles avoided bright light, even when presented on the side of the maze with which they had learned to associate a food. When light intensities of both sides were the same — irrespective of intensity — turtles chose the side they had previously learned to associate with the food reward. C. picta in our study showed a weak attraction to blue light and a strong avoidance of yellow light, a response generally consistent with previous work in sea turtles. Future studies should examine the ecological and evolutionary relevance of these decisions in field-oriented tests. [ABSTRACT FROM AUTHOR]

Around the margin of an artificial pond in Ottawa, Ontario, we found 25 Painted Turtles (Chrysemys picta) that appeared to have died over the course of two winters (17 during the first winter and eight during the second). We examined meteorological data to try to determine the cause of the mortality. Summer and fall rains were only slightly below normal in both years, suggesting water levels should have been close to normal. The winter air temperature was warmer than normal and winter snowfall was slightly above normal in both years. Unseasonable weather does not appear to be responsible for the winter mortality and the pond's maximum depth of 1.7 m should prevent freezing to the bottom. It is possible that the artificial nature of the pond creates suboptimal overwintering habitat, rendering the site an ecological trap; however, there is no direct evidence to support this theory. It is also possible that winter mortality of turtles is widespread at temperate wetlands, but that dead turtles were more detectable at this site because of the bare shoreline around the pond. Winter mass mortality events, if common, may represent an additional threat to turtle populations, which are declining from various anthropogenic threats. [ABSTRACT FROM AUTHOR]

Life-history theory predicts that investment in reproduction should increase as future reproductive potential (i.e., residual reproductive value [RRV]) decreases. Researchers have thus intuitively used age as a proxy for RRV and assume that RRV decreases with age when interpreting age-specific investment. Yet age is an imperfect proxy for RRV and may even be a poor correlate in some systems. We used a 31-year study of the nesting ecology of painted turtles (Chrysemys picta) to assess how age and RRV compare in explaining variation in a risky investment behavior. We predicted that RRV would be a better predictor of risky investment than age because RRV accounts for variation in future reproductive potential across life. We found that RRV was high in early life, slowly decreased until midlife, and then steadily decreased to terminal reproduction. However, age predicted risky behavior better than RRV. This finding suggests that stronger correlates of age (e.g., size) may be more responsible for this behavior in turtles. This study highlights that researchers should not assume that age-specific investment is driven by RRV and that future work should quantify RRV to more directly test this key element of life-history theory. [ABSTRACT FROM AUTHOR]

Environmental conditions during embryonic development affect morphology, behavior, and survival in turtles. Nest temperature also could affect posthatching traits of offspring, such as emergence behaviors. We monitored thermal conditions in painted turtle (Chrysemys picta) nests along the Mississippi River in Illinois to examine their influence on offspring survival and nest emergence. We recorded hourly temperatures within nest cavities during embryonic development in summer 2016 (n = 34) and after hatching through the following January (n = 15–20). Hatching success and posthatching survival appeared to be largely unaffected by thermal conditions recorded in nests. Emergence of neonates from nests was observed from 19 March through 12 May 2017. Onset of offspring emergence occurred later in the spring for nests with greater exposure to subzero temperatures in winter. For nearly all nests with live offspring, siblings did not emerge en masse, but instead departed the nest across multiple days. Nests with higher mean temperatures during incubation exhibited earlier mean emergence dates in spring, yet emergence duration was positively correlated with thermal maxima experienced in nests in fall and winter. Thus, thermal environments in nests at different times of year apparently elicited variation in spring emergence timing of C. picta hatchlings. [ABSTRACT FROM AUTHOR]

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 sequencing from turtles from across Ontario, with no clinical signs of illness. We found 2 positives with high viral load and 5 positives with low viral load. Histopathology found subtle histological changes. DNA sequences identified two types of frog virus 3 (FV3), and genome sequencing identified a ranavirus similar to wild-type FV3. Our results show that the virus has been present in Ontario's turtles as subclinical infections. • Positives turtles with high and low viral load based on qPCR. • Evidence of subclinical infection. • Histopathology found subtle histological changes. • DNA sequences identified two types of frog virus 3. • Genome sequencing identified a ranavirus similar to wild-type FV3. [ABSTRACT FROM AUTHOR]

A 16-yr-old male midland painted turtle (Chrysemys picta marginata) presented for evaluation of a crusted cervical lesion and conjunctivitis. The patient initially underwent several treatments of both topical and systemic antimicrobial therapies for dermatitis. Despite treatment guided by results of cytology, crust histopathology, and bacterial culture and sensitivity, dermal lesions were progressive, and a deep excisional biopsy was performed of the two largest lesions. Results of histopathology revealed an incompletely excised squamous cell carcinoma with secondary bacterial and fungal infections. Strontium-90 plesiotherapy was applied to all visible skin lesions, in addition to cryotherapy of a right-eyelid mass 5 wk later. These therapies provided a disease-free interval of less than 45 days in this patient. Because of progressive disease, the turtle was euthanized 7 wk after strontium-90 plesiotherapy. Results of necropsy revealed multifocal squamous cell carcinoma of the head, neck, and left forelimb with local neoplastic invasion and associated cellulitis and dermatitis. Treatment of multifocal cutaneous squamous cell carcinoma with strontium-90 and cryotherapy did not prevent disease progression in this turtle. [ABSTRACT FROM AUTHOR]

Developmental environments can have lasting effects on an individual’s phenotype. In many reptiles, for example, egg incubation temperature permanently determines offspring sex (temperature-dependent sex determination, TSD) and also influences a suite of morphological, physiological, and behavioral traits. Thus, the contributions of sex and incubation temperature to phenotypic variation are difficult to identify because these factors are confounded under TSD. We used chemical manipulations to experimentally decouple gonadal sex and incubation temperature in a turtle with TSD (Chrysemys picta) to examine their relative and interactive effects on variation in incubation duration and offspring size. We show that warm incubation temperature accelerates development as expected and that exogenous estradiol treatment to eggs further shortens incubation duration across all incubation temperatures. Moreover, estradiol unexpectedly induced male development, resulting in male offspring hatching sooner than female offspring. Variation in offspring size was also influenced by incubation temperature and gonadal sex, but interactions between these two variables were relatively small or nonsignificant. The fitness consequences of these effects are unknown, but we provide preliminary results from our attempts at examining the long-term and sex-specific effects of incubation temperature. Manipulative experimental approaches, combined with longer-term experiments that track individuals through reproduction, will provide novel insights into the adaptive significance of developmental plasticity in long-lived organisms. [ABSTRACT FROM AUTHOR]

Temperature-dependent sex determination, where egg incubation temperature irreversibly determines offspring sex, is a common sex-determining mechanism in reptiles. Weather is the primary determinant of temperature in reptile nests, yet the effects of weather are mediated through the nest microhabitat selected by the mother (e.g., overstory canopy cover). One potentially important aspect of the nest microhabitat is the physical substrate used for nesting. However, the influence of substrate type on nest temperature and offspring sex determination has never been experimentally assessed in the field. We incubated eggs of Painted Turtles (Chrysemys picta) in three substrate types similar to those commonly selected for nesting within our study population. Within a single study site, we constructed pits, which we refilled with loam, sand, or gravel. Then, we created artificial nests in each substrate type, and randomly assigned eggs to a substrate treatment. Substrate type influenced nest temperature and soil moisture, and affected incubation duration, but no other phenotype measured beyond offspring sex ratios. The cooler loam yielded the most male-biased outcome. This finding illustrates the potential importance of nesting substrate as a component of nest-site choice and as a factor in modeling future nest-temperature scenarios. [ABSTRACT FROM AUTHOR]

Abstract Determination of how carotenoid-based color patches change with pigmentary access is important to understanding color patch function in animals. We performed a carotenoid addition experiment on male painted turtles (Chrysemys picta) to determine if an increase in dietary carotenoids led to location-specific changes in painted turtle spot and stripe color. Turtles fed large quantities of carotenoids had increased yellow chroma in chin stripes and increased red chroma in the neck and carapace stripes, as well as reduced ultraviolet (UV) chroma in the neck (orange to the human eye) and fore -limb (red to the human eye) stripes. Turtles fed large quantities of carotenoid had reduced brightness (B 1) in the hind-limb stripes (red to the human eye) as well as reduced red and UV chroma in the post orbital spot of turtles (yellow to the human eye) compared to turtles fed moderate amounts of carotenoid. These results imply that integumentary spot and stripe colors are dependent upon carotenoid access, and increased lutein access leads to increased yellow and red chroma, as well as reduced ultra-violet chroma and brightness in male painted turtles. These results are discussed with respect to dietary access to carotenoids and color in other model systems, and the possibility that spot and stripe color functions as a visual signal. Highlights • Male painted turtles differ in stripe and spot spectra when fed a moderate vs large amount of dietary carotenoids. • Stripes and spots increase red and yellow chroma and decrease UV chroma and brightness in turtles fed large amounts of carotenoids compared to stripes and spots of turtles fed moderate amounts of carotenoids. [ABSTRACT FROM AUTHOR]

Taxa with large geographic distributions generally encompass diverse macroclimatic conditions, potentially requiring local adaptation and/or phenotypic plasticity to match their phenotypes to differing environments. These eco‐evolutionary processes are of particular interest in organisms with traits that are directly affected by temperature, such as embryonic development in oviparous ectotherms. Here we examine the spatial distribution of fitness‐related early life phenotypes across the range of a widespread vertebrate, the painted turtle (Chrysemys picta). We quantified embryonic and hatchling traits from seven locations (in Idaho, Minnesota, Oregon, Illinois, Nebraska, Kansas, and New Mexico) after incubating eggs under constant conditions across a series of environmentally relevant temperatures. Thermal reaction norms for incubation duration and hatchling mass varied among locations under this common‐garden experiment, indicating genetic differentiation or pre‐ovulatory maternal effects. However, latitude, a commonly used proxy for geographic variation, was not a strong predictor of these geographic differences. Our findings suggest that this macroclimatic proxy may be an unreliable surrogate for microclimatic conditions experienced locally in nests. Instead, complex interactions between abiotic and biotic factors likely drive among‐population phenotypic variation in this system. Understanding spatial variation in key life‐history traits provides an important perspective on adaptation to contemporary and future climatic conditions. Taxa with large geographic distributions generally encompass diverse macroclimatic conditions, potentially requiring local adaptation and/or phenotypic plasticity to match phenotypes to differing environments. Here we examine the spatial distribution of fitness‐related early life phenotypes across the range of a widespread vertebrate, the painted turtle (Chrysemys picta) under common‐garden conditions. Our findings suggest that these macroclimatic proxies may be unreliable surrogates, and instead, it is likely that complex interactions between abiotic and biotic factors drive among‐population phenotypic variation in this system. Understanding spatial variation in key traits provides important perspective on adaptation to climatic conditions and potential future phenotypic responses to projected climate change. [ABSTRACT FROM AUTHOR]

The painted turtle (Chrysemys picta) is widely distributed from coast to coast in North America with each of four subspecies generally occupying different regions. In the southwestern USA and northern Mexico, where C. p. bellii is the expected native race, populations are small and widelyscattered. Introduced populations of other painted turtle subspecies are reported from various locations in the USA. We discovered a small but dense introduced population of C. p. marginata on the Colorado Plateau in northern Arizona, a region with few, if any, turtles due to aridity and an elevated topography with little surface water. The turtles were in a remote pond constructed to provide cattle with water. Chrysemys p. marginata occur naturally east of the Mississippi River, over 2,000 km away. The nearest native population of C. p. bellii in Arizona is over 160 km away. We observed nesting females, juveniles, and the presence of shelled eggs in females via Xradiography confirming a self-sustaining population. The body sizes and nesting season we observed were consistent with data for those variables from native populations of the taxon. It is unknown exactly how the turtles came to be established in such a remote location, but it is unlikely that they will spread due to the scarcity of perennial water sources in the semi-arid region. Due to increasing drought frequency and duration in the region, small populations like this one, introduced into a novel environment, may be bellwethers for monitoring the effects of climate change. [ABSTRACT FROM AUTHOR]

Painted Terrapin (Batagur borneoensis Schlegel and Muller 1845) conservation in the coastal area of Aceh Tamiang Regency faces difficulties because it involves many stakeholder. The objective of this study were to analyze stakeholder interest, influences and describe the relationship among stakeholder in the conservation of Batagur borneoensis at Aceh Tamiang District. The study was conducted in Aceh Tamiang District and respondents were selected using purposive sampling method. The data obtained using questionnaire, interview, and direct observation were analyzed with stakeholder clasification matrix, stakeholder interaction matrix and descriptive analysis. The results showed that there are twenty-seven stakeholder involved in the conservation of Batagur borneoensis which can be categorized as subjects, key players, context setters, and crowds. To achieve the management objectives of Batagur borneoensis conservation, stakeholder engagement needs to be improved through collaboration among key players, participation all key stakeholder, and community empowerment. [ABSTRACT FROM AUTHOR]

Animals aggregate to reduce predation risk, facilitate mating, and access resources with patchy distributions. During a long-term study of turtle populations in the Santa Fe River (SFR) ecosystem in northern Florida, we observed a large aggregation of turtles at Gilchrist Blue Springs Park (GBSP) in August-October 2013 and again in March-May 2014. On 8 September 2013, we hand-captured 496 turtles of 5 species in GBSP. The Suwannee cooter ( Pseudemys concinna suwanniensis) was the most abundant species in the sample, with 477 individuals representing all demographic groups. Density of this species was 530 turtles/ha and biomass was 2242 kg/ha. We hypothesize that hydrological changes in the SFR basin contributed to the temporary turtle aggregations at GBSP. The 113-km SFR originates as a tannin-stained blackwater stream, but receives input of clear water from ≥ 45 artesian springs in its lower 37 km. Heavy rainfall in the upper SFR basin from Tropical Storm Debby in June 2012 resulted in a large influx of tannic water that overwhelmed the capacity of the springs to dilute the river water. This storm in combination with additional episodes of heavy rainfall and declining spring flows led to an unusually long (34-mo) tannic period in the typically clear lower 37 km of the SFR. The resulting loss of most submerged aquatic macrophytes in the river due to insufficient sunlight may have been the stimulus that led the herbivorous P. c. suwanniensis to seek food in one of the few locations that had abundant submerged aquatic vegetation in 2013 and 2014. Turtles previously marked upriver (to 16 km) and downriver (to 4.6 km) from GBSP were in the aggregation, suggesting the individuals gathered at GBSP represented a large portion of the SFR P. c. suwanniensis population. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is an increasingly used non-invasive molecular tool for detecting species presence and monitoring populations. In this article, we review the current state of non-avian reptile eDNA work in aquatic systems, and present a field experiment on detecting the presence of painted turtle (Chrysemys picta) eDNA. Thus far, turtle and snake eDNA studies have shown mixed results in detecting the presence of these animals under field conditions. However, some instances of low detection rates and non-detection occur for these non-avian reptiles, especially for squamates. We explored non-avian reptile eDNA quantification by sampling four lentic ponds with different densities (0 kg/ha, 6 kg/ha, 9 kg/ha, and 13 kg/ha) of painted turtles over three months to detect differences in eDNA using a qPCR assay amplifying the COI gene of the mtDNA genome. Only one sample of the highest-density pond amplified eDNA for a positive detection. Yet, estimates of eDNA concentration from pond eDNA were rank-order correlated with turtle density. We present the “shedding hypothesis„—the possibility that animals with hard, keratinized integument do not shed as much DNA as mucus-covered organisms—as a potential challenge for eDNA studies. Despite challenges with eDNA inhibition and availability in water samples, we remain hopeful that eDNA can be used to detect freshwater turtles in the field. We provide key recommendations for biologists wishing to use eDNA methods for detecting non-avian reptiles.

Maternal stressors can play an integral role in offspring development and ultimate behaviors in many vertebrates. Increased circulating stress avoidance hormones can be reflected in elevated concentrations in ova, thus providing a potential mechanism for maternal stress to be transmitted to offspring even in taxa without parental care. In this study, we assessed the potential impacts of augmented stress avoidance hormones on offspring development and anti-predator behaviors in a freshwater turtle, Chrysemys picta . We exposed C. picta eggs to biologically relevant amounts of the stress avoidance hormone, corticosterone, as a proxy for maternal stressors. We allowed the eggs to incubate in the field, then measured offspring phenotypes, conducted performance trials, and simulated nest emergence in a field experiment. Exogenous corticosterone reduced survivorship to hatch, but did not affect incubation duration, offspring size, overwinter survival, or size after hibernation. In performance trials, this hormone treatment reduced the frequency of righting, yet enhanced the righting speed of neonates. Regardless, these performance differences did not detectably alter survivorship in the nest emergence experiment. These results lend insight into the potential effects of maternal stress levels on offspring phenotypes, as well as the robustness of offspring fitness to altered levels of maternal stress in freshwater turtles. [ABSTRACT FROM AUTHOR]

We examined captures of Painted Turtle (Chrysemys picta) in Algonquin Provincial Park, Ontario, Canada, during the understudied summer-autumn transition period (August-September). The proportion of captured male turtles increased relative to the proportion of females during the late summer and early autumn sampling period, leading to male-biased capture rates in a population with a strongly female-biased sex ratio. We consider explanations for the capture bias in relation to sex-specific activity patterns and briefly discuss the implications of sampling period on the outcome of population structure studies. [ABSTRACT FROM AUTHOR]

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 recently, it was found that brief subzero chilling of winter-acclimated hatchlings decreases subsequent chilling-induced mortality, increases blood concentrations of glucose and lactate, and protects the brain from cryoinjury. Here, we further characterize that phenomenon, termed 'cold conditioning', by exposing winter-acclimated hatchling turtles to −3.5, −7.0, or −10.5 °C gradually or repeatedly via daily thermal fluctuations over the course of 5 days and assessing their survival of a subsequent cold shock to a discriminating temperature of −12.7 °C. To better understand the physiological response to cold conditioning, we measured changes in glucose and lactate concentrations in the liver, blood, and brain. Cold conditioning significantly increased cold-shock survival, from 9% in reference turtles up to 74% in cold-conditioned turtles, and ecologically relevant daily thermal fluctuations were at least as effective at conferring cryoprotection as was gradual cold conditioning. Cold conditioning increased glucose concentrations, up to 25 μmol g, and lactate concentrations, up to 30 μmol g, in the liver, blood, and brain. Turtles that were cold conditioned with daily thermal fluctuations accumulated more glucose in the liver, blood, and brain, and had lower brain lactate, than those gradually cold conditioned. Given the thermal variation to which hatchling painted turtles are exposed in winter, we suggest that the supplemental protection conferred by cold conditioning, especially that induced by daily thermal fluctuations, may be important for their overwinter survival. Investigation into the duration of the cold-conditioning induced protection and its occurrence in natural field conditions is needed to better understand its ecological significance. We suggest that future work exploring the underlying mechanisms of cold conditioning should focus on non-colligative effects of glucose, expression of small Hsps, changes in membrane structure, and ion homeostasis. [ABSTRACT FROM AUTHOR]

Theory predicts prey should flee to safety when the fitness benefits of flight meet or exceed the costs. Empirical work has shown the importance of predation risk (e.g., predator behavior, distance to refuge) to prey flight behavior. However, less is known about the influence of flight costs. We monitored nesting Painted Turtles ( Chrysemys picta (Schneider, 1783)) to examine their response to a human observer (potential predator) depending on the distance between a turtle and an observer, distance between a turtle and water (i.e., refuge), and nesting stage at the time of the encounter (i.e., searching for a nest site vs. constructing a nest). We found no evidence that the distance to an observer influenced flight decisions. However, turtles were less likely to flee as the distance to water increased, and turtles already constructing nests were more likely to continue nesting than those still searching for nest sites. Turtles that traveled farther from water and that were constructing nests may have continued nesting because they had invested considerable energy and were close to completing oviposition. Thus, the fitness benefits of being closer to successful oviposition may outweigh the costs of increased vulnerability to predators during this important and vulnerable period of reproduction. [ABSTRACT FROM AUTHOR]

The ability to identify the sex of animals accurately is important in population studies. Emydid turtles (Testudines: Emydidae) demonstrate a number of sexually dimorphic characters, including head (cranial) size and structure. Field observations from a long-term study of midland painted turtles ( Chrysemys picta marginata) in Algonquin Provincial Park, Ontario, Canada, suggested distinct differences in external head morphology between the sexes. We evaluated these putative sexual differences in C. picta head morphology by conducting a visual questionnaire involving human observers of varying levels of experience (novice, beginner, intermediate, and advanced). Observers were capable of distinguishing the sexes based solely on head morphology with a high degree of accuracy (between 79% and 86% success) across experience levels. Observers identified head shape as a defining character distinguishing the sexes. We suggest that visual questionnaires are a quantifiable method of assessing dimorphic characters that can be used in addition to traditional morphometrics or geometric morphometrics to demonstrate a visual, rather than simply statistical, difference among characters and sexes. Despite the breadth of research conducted on C. picta, our study is among the first to describe, assess, and discuss the functional significance of head dimorphism in this model species. [ABSTRACT FROM AUTHOR]

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 demands are highest in embryos. A brief, but severe, hypoxic event (5% O2 for 0.5 h) moderately affected embryo growth, causing a 13% reduction in mass (relative to a normoxic control). The same condition had no effect during day 27; instead, a nearly anoxic event (1% O2 for 72 h) caused a 5% mass reduction. All embryos survived the egg incubation period. Our study supports the assumption that reptilian embryos are resilient to intermittently low O2 in subterranean nests. Further work is needed to ascertain responses to suboptimal O2 levels while undergoing dynamic changes in developmental physiology. [ABSTRACT FROM AUTHOR]