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The blood biochemistry of overwintering diamondback terrapins (Malaclemys terrapin)

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... Terrapins experience a broad range of salinities (11-35 psu) in their coastal habitats (Dunson, 1970;Harden and Williard, 2012), and provide a good illustration of how morphological, behavioral and physiological features contribute to osmoregulation in estuarine environments. Body fluid osmotic pressure of terrapins under natural conditions falls within the range 300-350 mOsm, and is typically hyposmotic to the surrounding aquatic environment (Harden et al., 2015). Passive exchange of water and salts between terrapins and their environment is minimized as a result of low integument permeability (Robinson and Dunson, 1976). ...
... Terrapins exhibit distinct seasonal patterns in behavior and habitat utilization, which appear to be driven largely by variations in environmental temperature (Yearicks et al., 1981;Harden and Williard, 2012). At water temperatures (T W ) of ≤20°C, terrapins enter a dormant state characterized by mud burial, hypophagy and decreased metabolic capacity (Southwood Williard and Harden, 2011;Harden and Williard, 2012;Harden et al., 2015). Overwintering in the mud may reduce passive exchange of water and salts across the integument and a reduction in feeding decreases active uptake of salts from the environment (Davenport and Magill, 1996); these behavioral changes contribute to the terrapin's ability to maintain osmotic balance during a period when both metabolic capacity and resource availability are low (Harden et al., 2015). ...
... At water temperatures (T W ) of ≤20°C, terrapins enter a dormant state characterized by mud burial, hypophagy and decreased metabolic capacity (Southwood Williard and Harden, 2011;Harden and Williard, 2012;Harden et al., 2015). Overwintering in the mud may reduce passive exchange of water and salts across the integument and a reduction in feeding decreases active uptake of salts from the environment (Davenport and Magill, 1996); these behavioral changes contribute to the terrapin's ability to maintain osmotic balance during a period when both metabolic capacity and resource availability are low (Harden et al., 2015). During the warm weather active season, terrapins may rely more heavily on active ion extrusion via the salt glands, given the higher rates of passive and active water and salt exchange with the environment and the need for continual energy intake to support higher metabolic demands (Baker et al., 2013;Harden et al., 2014). ...
Article
The diamondback terrapin is the only temperate turtle species that exclusively inhabits estuarine environments. Morphological, behavioral and physiological features contribute to the terrapin's ability to regulate body fluid osmotic pressure in a euryhaline environment. Low integument permeability combined with aquatic-terrestrial shuttling behavior limits passive exchange of water and salts with the environment, and terrapins regulate active uptake of salts via alterations in drinking and feeding behavior. The lachrymal salt gland facilitates excretion of excess sodium (Na+) and chloride (Cl-) ions through active transport mechanisms. We investigated body fluid dynamics, oxygen consumption (V̇O2 ) and osmotic status of terrapins exposed to an acute increase in salinity (12 to 35 psu) at 10 and 25°C to gain insight into the relative importance of behavioral versus physiological osmoregulatory adjustments over a range of seasonally relevant temperatures. Linear mixed models were used to evaluate the effects of experimental temperature, salinity and mass. Overall, temperature effects were stronger than salinity effects. Terrapins acclimated to 25°C had significantly lower blood osmolality and Na+, and higher water turnover rates, daily water flux (DWF) and V̇O2 compared with terrapins acclimated to 10°C. Salinity effects were restricted to DWF, which significantly decreased in response to acute exposure to 35 psu. Our results support the notion that behavioral adjustments predominate in the osmoregulatory strategy of terrapins.
... Several studies have aimed to understand salt tolerance in terrapins by focusing on a specific morphological, behavioral, or physiological aspect of osmoregulation (see Harden and Williard 2018, for review). Briefly, Diamond-backed Terrapins cannot concentrate salts in urine; therefore, to regulate body fluid composition, they must integrate unique physiological capabilities with adaptive behavioral strategies (Hildebrandt 2001;Harden et al. 2015). Terrapin integument is less salt permeable than that of freshwater turtles (Robinson and Dunson 1976). ...
... These behaviors were consistent with findings of prior experimental studies of terrapins (Davenport and Macedo 1990; Davenport and Ward 1993;Davenport and Magill 1996;Williard et al. 2019), and demonstrate allostatic responses to reduce exposure to, or limit the effects of, a hypersaline environment. Spending time out of saltwater may allow hatchlings to rehydrate in humid air or simply avoid saltwater uptake (Harden et al. 2015). Appetite suppression reduces saltwater intake through decreasing daily water flux (Williard et al. 2019); in other vertebrate species, feeding is inhibited during advanced stages of dehydration because it increases requirements for water (Watts and Boyle 2010;Wright et al. 2013;Lillywhite 2017). ...
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Diamond-backed terrapins inhabit coastal salt marshes along the eastern and Gulf coasts of North America. Terrapins are adapted to intermediate salinities yet frequently face saltwater-inundated marsh habitat exceeding 25 ppt (or grams/kilogram). We investigated the effect of salinity on the growth of hatchling terrapins and on their compensatory responses to salinity stress. We randomly assigned 30 terrapin hatchlings each to one of five salinity treatments (1, 5, 10, 20, or 35 ppt). Over 75 d, we regularly monitored behavior, appetite, and changes in growth; and calculated ratios of heterophils to lymphocytes (H:L ratio) to assess responses to prolonged salinity stress. Consistent with prior studies, chronic exposure to high salinity significantly reduced hatchling growth. Hatchlings in 20-ppt and 35-ppt salinities exhibited appetite suppression and saltwater avoidance and were more likely to show freshwater-seeking behaviors. H:L ratios were higher among hatchlings in 20-and 35-ppt salinities, consistent with a corticosterone-driven stress response to sustained high-salinity exposure, which may play a role in limiting growth. Our findings suggest hatchling growth and distribution among local habitats will vary spatially depending on habitat salinity and freshwater accessibility. The growth-limiting effects of chronically high salinity or limited access to freshwater could therefore increase hatchling mortality and be an important driver of spatial variation in terrapin demography and abundance. However, when freshwater sources are available, compensatory behaviors might reduce growth-limiting effects. Terrapin recruitment is likely to be impacted as rising sea levels, increased human water use, land development, and other anthropogenic changes alter freshwater inputs to coastal marshes.
... Freshwater turtles exploiting estuarine habitats may use a combination of compensatory and evasive and behavioural mechanisms to reduce exposure to high salinity (Hart and Lee, 2006;Harden et al., 2015), and some species also possess clear adaptive physiological and homeostatic mechanisms to tolerate elevated saline through reducing uptake of salt and loss of water (Dunson and Mazzotti, 1989). In this study, we assessed the tolerance and physiological responses of two species of Australian freshwater turtles, Emydura macquarii and Chelodina expansa, both of which occur extensively throughout the Murray-Darling Basin in lengths of the river system far removed from the lower estuary of the Basin, to exposure to brackish water that was hyperosmotic to their body fluids. ...
... Therefore, the persistence of freshwater turtles in saline environments may be limited if they cannot access freshwater, and this finding raises the need to understand the effect of extended or more frequent periods of exposure to higher salinity. Other environment factors can have effects on blood chemistry in vertebrates, and the capacity of turtles to tolerate salt may change as a result of temperature, dormancy and acclimation (Muir et al., 2008;Harden, et al., 2015). The fitness impact of limited periods of elevated salinity (which in this study had no obvious adverse effects) may be different from higher-frequency or sustained intervals of elevated saline conditions. ...
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Freshwater biota experience physiological challenges in regions affected by salinization, but often the effects on particular species are poorly understood. Freshwater turtles are of particular concern as they appear to have limited ability to cope with environmental conditions that are hyperosmotic to their body fluids. Here, we determined the physiological responses of two Australian freshwater chelid turtles, Emydura macquarii and Chelodina expansa, exposed to freshwater (0‰) and brackish water (15‰, representing a hyperosmotic environment). Brackish water is common in the Murray–Darling River Basin within the natural range of these species in Australia during periods of drought, yet it is unknown how well these species tolerate saline conditions. We hypothesized that these turtles would be unable to maintain homeostasis in the 15‰ water treatment and would suffer osmotic loss of water, increased ionic concentrations and a decrease in body mass. Results revealed that these turtles had elevated plasma concentrations of sodium, chloride, urea and uric acid in the plasma. Plasma ionic concentrations increased proportionally more in E. macquarii than in C. expansa. Individuals of both species reduced feeding in 15‰ water, indicating that behaviour may provide an additional means for freshwater turtles to limit ion/solute influx when in hyperosmotic environments. This osmoregulatory behaviour may allow for persistence of turtles in regions affected by salinization; however, growth rates and body condition may be affected in the long term. Although we demonstrate that these turtles have mechanisms to survive temporarily in saline waters, it is likely that sustained salinization of waterways will exceed their short- to medium-term capacity to survive increased salt levels, making salinization a potentially key threatening process for these freshwater reptiles.
... Our discovery of the absence of cloacal bursae in the brackish species M. terrapin is consistent with this reasoning. Remarkably, terrapins maintain steady osmoregulation even during their inactive winter season, when they typically remain buried in mud in intertidal or subtidal estuarine waters with virtually no access to freshwater from rainfall, ingested food, etc. (Harden et al., 2015). Cloacal bursae are plesiomorphically present in Emydidae, which we confirmed in the taxa T. scripta and G. geographica, both closely related to M. terrapin (Thomson et al., 2021), so their absence in M. terrapin represents an independent loss. ...
... Dispersal occurs postnesting, with the variation in the scale and frequency of movement being linked to sex, size, prey availability, and tide cycle (Tucker et al., 2018). Finally, between October and December (latitude-dependent), DBT move to winter brumation sites where they generally remain dormant for several months (Yearicks et al., 1981;Brennessel, 2006;Hardin et al., 2015;Castro-Santos et al., 2019). Thus, DBT themselves exhibit spatiotemporal variation in behaviors and movement that depend on sex, age or stage, and timing. ...
Article
The status, size, and density of Malaclemys terrapin (Diamondback Terrapin) populations along the Atlantic coast have been reported by most states as unknown or declining. Robust demographic or population data are lacking, with even less information available on their spatial ecology. Spatial capturerecapture (SCR) methods explicitly incorporate spatial processes, providing a formal link between encounter data and space use. Despite the widespread adoption of SCR across ecological disciplines, it has yet to be applied to turtle populations. We present the first application of SCR methods to Diamondback Terrapins by analyzing data collected from two known activity areas in the tidal marsh systems of Wellfleet Bay, Massachusetts. We found that Terrapin detection was positively associated with survey effort at both sites. Detection was also influenced by day of season, tide cycle, the time of tide, survey time relative to the tide, cloud cover, and windspeed. Density and space use differed markedly between the two sites: the estimated density in The Run was 9 individuals/ha with a space use parameter of 309 m, compared to 59 individuals/ha and a space use parameter of 107 m in The Cove. Sex structure was female-biased, with a sex ratio of 0.34 and 0.18 males in The Run and The Cove, respectively. We demonstrate the utility in using SCR methods in turtles, specifically Diamondback Terrapins, to produce comparable estimates of detection and population size and density, while simultaneously providing inference on differential space-use and detection resulting from variation in both behavior and sampling conditions.
... Following the statistical methods of Rayl et al. (2020), a Cox proportional hazards model was created to identify health variables that act as predictors of a longer survival period in the wild after release from captivity. The 16 variables included in the model were the 15 physiological metrics used for statistical analyses and a weighted mean carapace temperature, T c (for calculation of mean weighted T c , see Harden et al. 2015Harden et al. , 2018, which may act as an indicator of surface and/or boldness behavior (see Kashon and Carlson 2018). Since RR 2016 and RR 2017 juveniles were captured for monthly blood draws, individual turtles provided repeated measures over time. ...
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Conservation translocations are important in maintaining viable wildlife populations of vulnerable species within their indigenous ranges. To be effective, population restoration efforts (e.g., head start programs) must consider the species' life history, regional ecology, and physiology and the health status of wild and translocated populations. The decline of Blanding's turtles (Emydoidea blandingii) has prompted the initiation of head start programs, but the health and short-term survival of head-started juveniles released to the wild is largely unknown. From May to October 2016 and 2017, we radio tracked captive-reared, recently released juvenile Blanding's turtles and monitored their survivorship and monthly physiological health. We aimed to (1) compare physiological metrics of juveniles before and after release from captivity and between head-started cohorts, (2) identify seasonal trends in physiological metrics of recently released juveniles, (3) compare physiological metrics of recently released and formerly released juveniles, and (4) identify predictors of juvenile survivorship after release from captivity. Juvenile short-term survival was low compared with other studies. Most physiological metrics did not change after release from captivity, negating significant juvenile stress before or after release. Physiological metrics for recently released cohorts varied seasonally, suggesting that these juveniles were likely in good health. Some physiological metrics differed between recently released and formerly released juveniles, demonstrating a potential postrelease acclimatization period. Finally, no physiological metrics significantly predicted survival, but surviving juveniles had a higher percentage of fat. In all, juvenile deaths were not due to poor turtle health but rather to predation from human-subsidized mesocarnivores. Therefore, head-started juvenile Blanding's turtles released in suburban areas may benefit from antipredator training and mesocarnivore control at release sites.
... To survive in saline waters, a few freshwater turtles are known to implement various behavioural and physiological mechanisms that allow them to temporarily occupy brackish water environments >0.5 ppt salinity for periods of hours to months, depending on the species (Agha et al., 2018). These include moving between saline and freshwater habitats, reducing feeding and drinking, increasing plasma osmotic pressure relative to external environments by increasing plasma urea concentration and in some cases using a specialized lachrymal gland to excrete excess salt (Bower et al., 2016;Gilles-Baillien, 1970;Harden et al., 2015). While these mechanisms are effective means for tolerating saline waters for a few freshwater turtle species (Bower et al., 2016;Dunson and Dunson, 1975), they are often ineffective for many others that are highly sensitive to salinities >10 ppt (Agha et al., 2018). ...
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Sea-level rise, drought and water diversion can all lead to rapid salinization of freshwater habitats, especially in coastal areas. Increased water salinities can in turn alter the geographic distribution and ecology of freshwater species including turtles. The physiological consequences of salinization for freshwater turtles, however, are poorly known. Here, we compared the osmoregulatory response of two geographically separate populations of the freshwater Western Pond Turtle (Actinemys marmorata)—a species declining across its range in western North America—to three constant salinities: 0.4 ppt, 10 ppt and 15 ppt over 2 weeks. We found that turtles from a coastal estuarine marsh population regulated their plasma osmolality at lower levels than their conspecifics from an inland freshwater creek population 45 km away. Plasma osmolalities were consistently lower in estuarine marsh turtles than the freshwater creek turtles over the entire 2-week exposure to 10 ppt and 15 ppt water. Furthermore, estuarine marsh turtles maintained plasma osmolalities within 1 SD of their mean field osmolalities over the 2-week exposure, whereas freshwater creek turtles exceeded their field values within the first few days after exposure to elevated salinities. However, individuals from both populations exhibited body mass loss in 15 ppt water, with significantly greater loss in estuarine turtles. We speculate that the greater ability to osmoregulate by the estuarine marsh turtles may be explained by their reduced feeding and drinking in elevated salinities that was not exhibited by the freshwater creek population. However, due to mass loss in both populations, physiological and behavioural responses exhibited by estuarine marsh turtles may only be effective adaptations for short-term exposures to elevated salinities, such as those from tides and when traversing saline habitats, and are unlikely to be effective for long-term exposure to elevated salinity as is expected under sea-level rise.
... Flexible behaviour of multiple freshwater turtle species in the absence of physiological adaptations allows them to temporarily occupy brackish water environments . Behavioural mechanisms include activities like movements between saline and freshwater areas, frequent retreats to freshwater sources higher upstream, and reduced feeding and drinking that would result in ingestion of higher salinity water (Hart & Lee, 2006;Harden, Midway, & Williard, 2015;Bower et al., 2016). For example, M. terrapin and B. baska can identify high-salinity conditions and avoid drinking or feeding when water salinity is too high (Davenport & Ward, 1993). ...
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The projected rise in global mean sea levels places many freshwater turtle species at risk of saltwater intrusion into freshwater habitats. Freshwater turtles are disproportionately more threatened than other taxa; thus, understanding the role of salinity in determining their contemporary distribution and evolution should be a research priority. Freshwater turtles are a slowly evolving lineage; however, they can adapt physiologically or behaviourally to various levels of salinity and, therefore, temporarily occur in marine or brackish environments. Here, we provide the first comprehensive global review on freshwater turtle use and tolerance of brackish water ecosystems. We link together current knowledge of geographic occurrence, salinity tolerance, phylogenetic relationships, and physiological and behavioural mechanisms to generate a baseline understanding of the response of freshwater turtles to changing saline environments. We also review the potential origins of salinity tolerance in freshwater turtles. Finally, we integrate 2100 sea level rise (SLR) projections, species distribution maps, literature gathered on brackish water use, and a phylogeny to predict the exposure of freshwater turtles to projected SLR globally. From our synthesis of published literature and available data, we build a framework for spatial and phylogenetic conservation prioritization of coastal freshwater turtles. Based on our literature review, 70 species (∼30% of coastal freshwater turtle species) from 10 of the 11 freshwater turtle families have been reported in brackish water ecosystems. Most anecdotal records, observations, and descriptions do not imply long‐term salinity tolerance among freshwater turtles. Rather, experiments show that some species exhibit potential for adaptation and plasticity in physiological, behavioural, and life‐history traits that enable them to endure varying periods (e.g. days or months) and levels of saltwater exposure. Species that specialize on brackish water habitats are likely to be vulnerable to SLR because of their exclusive coastal distributions and adaptations to a narrow range of salinities. Most species, however, have not been documented in brackish water habitats but may also be highly vulnerable to projected SLR. Our analysis suggests that approximately 90% of coastal freshwater turtle species assessed in our study will be affected by a 1‐m increase in global mean SLR by 2100. Most at risk are freshwater turtles found in New Guinea, Southeast Asia, Australia, and North and South America that may lose more than 10% of their present geographic range. In addition, turtle species in the families Chelidae, Emydidae, and Trionychidae may experience the greatest exposure to projected SLR in their present geographic ranges. Better understanding of survival, growth, reproductive and population‐level responses to SLR will improve region‐specific population viability predictions of freshwater turtles that are increasingly exposed to SLR. Integrating phylogenetic, physiological, and spatial frameworks to assess the effects of projected SLR may improve identification of vulnerable species, guilds, and geographic regions in need of conservation prioritization. We conclude that the use of brackish and marine environments by freshwater turtles provides clues about the evolutionary processes that have prolonged their existence, shaped their unique coastal distributions, and may prove useful in predicting their response to a changing world.
... Sexes were pooled for all blood biochemical variables except iCalcium (iCalcium female and iCalcium male ), which can be elevated in gravid females (Kimble and Williams 2012). We calculated T c as a weighted mean of daily mean T c readings recorded 7 d prior to blood sampling (Harden et al. 2015). Not all of the 20 turtles in this study consistently had attached iButtons; thus, 15 (three females and 12 males) were used in the T c linear model analyses. ...
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Blood biochemical and hematology analyses are helpful indicators of the physiologic health of animals, particularly when making conservation and management decisions for threatened species. In this study, we 1) established blood biochemical reference intervals for two populations of threatened, free-ranging ornate box turtles ( Terrapene ornata) in northern Illinois during their active season and 2) examined the effects of individual carapace temperature ( Tc) on blood biochemical variables by using a Bayesian hierarchic framework. Individual blood variables differed throughout the active season (May-September 2015), but there were few distinct patterns in concentrations over time. When controlling for individual variability, blood biochemical variables potassium, sodium, chloride, ionized calcium, hematocrit (percentage of packed cell volume), and osmolality showed no effect of Tc(i.e., slope estimates for these variables were not credibly different from zero) and had little individual variation. Glucose and blood urea nitrogen (BUN) were found to have slopes credibly different from zero, with glucose having an estimated positive slope and BUN having an estimated negative slope, suggesting different relationships in response to Tcwhen controlling for individual variability. These physiologic blood data will serve as important baseline reference values for the clinical evaluation of wild ornate box turtles presented for veterinary care or for comparison to other studies of wild populations. Further, this study highlights the importance of considering individual-level effects (e.g., Tc) on physiologic health variables.
Chapter
Because the salt concentration of body fluids in aquatic vertebrates differs from that of their environment, they face net influx or efflux of water and salt across their permeable skin or exposed membranes. In fishes, these diffusional movements of both salts and water largely involve the gills. Other vertebrates have less permeable body surfaces, but water and salts are gained in drinking that is incidental to eating prey, which also can be an important source of salt intake. Kidneys function importantly in freshwater fishes to remove excess water, and ions are actively transported inwards across gill tissue as well as acquired in food. Marine fishes tend to dehydrate in seawater, so they drink seawater to make up a water deficit and secrete excess salt across the gills. Marine elasmobranch fishes accumulate urea in body fluids to minimise the gradient for osmotic exchange and secrete excess ions via a specialised rectal gland that functions accessory to the kidney. In other vertebrates, inhabitants of fresh water must counteract a key problem of acquiring sufficient ions while excreting nitrogenous waste as ammonia or urea, whereas marine species must avoid excess salt intake while avoiding dehydration. Vertebrates without gills have evolved either extrarenal salt glands that excrete excess salt, or in the case of mammals, a specialised kidney that can excrete highly concentrated urine. Relatively few, non-fish taxa drink seawater as a route for water gain, while most others have dependency on dietary, metabolic or free drinking water. • Osmoregulation involves the maintenance of volume, distribution and ionic composition of body fluids in organisms. • With the exception of hagfish, extant vertebrates maintain osmotic concentrations of body fluids at levels that are roughly one-third that of seawater. • Aquatic vertebrates living in fresh water must counteract excessive influx of water and losses of ions to the surrounding environment, whereas those living in marine environments tend to dehydrate and gain excess salt. • Freshwater fishes eliminate excess water by means of producing a copious flow of dilute urine, while acquiring ions from surrounding water by transporter mechanisms located in the gills. • Marine fishes acquire needed water by drinking seawater and excreting excess salt gained by diffusion and drinking by transport mechanisms in the gills. • Marine vertebrates other than fishes and mammals have evolved extrarenal salt glands that excrete excess salts, and water is gained largely from dietary, metabolic and freshwater drinking sources. • Marine mammals excrete salt loads and urea from kidneys that have effective concentrating abilities, while gaining water from diet and metabolism.
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Blood gas, pH, and lactate data are often used to assess the physiological status and health of fish and can often be most valuable when blood samples are analyzed immediately after collection. Portable clinical analyzers allow these measurements to be made easily in the field. However, these instruments are designed for clinical use and thus process samples at 37 degrees C. A few studies have validated the use of portable clinical analyzers for assessing blood gases and acid-base profiles in teleosts, but equivalent data are not available for elasmobranchs. We therefore examined the relationship of blood gas, pH, and lactate values measured with an i-STAT portable clinical analyzer with those measured using standard laboratory blood gas (thermostatted to 25 degrees C) and lactate analyzers in samples taken from three species of carcharhiniform sharks. We found tight correlations (r2 > 0.90) between these methods for pH, pO2, pCO2, and lactate level values. We thus developed species-specific equations for converting blood values measured with an i-STAT portable clinical analyzer to those taken at 25 degrees C. Additional studies need to address a wider range of temperatures and elasmobranch species.
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The doubly labeled water (DLW) method for studying energy and water balance in field-active animals is not feasible for freshwater animals during aquatic activities, but several species of nominally aquatic reptiles leave wetlands for several critical and extended behaviors, where they face challenges to their energy and water balance. Using DLW, we studied energy and water relations during terrestrial estivation and movements in the eastern long-necked turtle (Chelodina longicollis), a species that inhabits temporary wetlands in southeastern Australia. Water efflux rates of 14.3-19.3 mL (kg d)(-1 ) during estivation were nearly offset by influx, indicating that turtles did not maintain water balance while terrestrial, though dehydration was slow. Estivation energy expenditure declined over time to 20.0-24.6 kJ (kg d)(-1) but did not indicate substantial physiological specializations. Energy reserves are predicted to limit survival in estivation to an estimated 49-261 d (depending on body fat), which is in close agreement with observed bouts of natural estivation in this population. The energy cost and water flux rates associated with overland movement behavior ranged from 46 to 99 kJ (kg d)(-1 ) and from 21.6 to 40.6 mL (kg d)(-1), respectively, for turtles moving 23-34 m d(-1). When a wetland dries, a turtle that forgoes movement to other wetlands can save sufficient energy to fuel up to 134 d in estivation. The increasing time in estivation with travel distance gained in this energy "trade-off" fits our previous observations that more turtles estivate when longer distances must be traveled to the nearest permanent lake, whereas emigration is nearly universal when only short distances must be traversed. The DLW method shows promise for addressing questions regarding the behavioral ecology and physiology of freshwater turtles in terrestrial situations, though validation studies are needed.
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The big-headed turtle Platysternon megacephalum is a stream-dwelling species whose ecology is poorly known. We carried out field and laboratory investigations to determine field body temperatures and thermal preference of this species. In the field, the body temperatures of the turtles conformed to the water temperature, with little diel variation in either summer or au-tumn. Over the diel cycle, the mean body temperatures ranged from 20.8°C to 22.2°C in summer and from 19.3°C to 21.2°C in autumn; the highest body temperatures ranged from 22.1°C to 25.0°C in summer and from 20.6°C to 23.8°C in autumn. In the laboratory, the preferred body temperature (Tp) was 25.3°C. Food intake was maximized at 24.0°C, whereas locomotor perfor-mance peaked at 30.0°C. Consequently, Tp was closer to the thermal optimum for food intake than for locomotion. Therefore, this freshwater turtle has relative low field body temperatures corresponding to its thermal environment. In addition, the turtle prefers low temperatures and has a low optimal temperature for food intake.
Article
Ranging from Cape Cod to nearly the Texas-Mexico border, the diamondback terrapin (Malaclemys terrapin) is the only species of North American turtle restricted to estuarine systems. Despite this extensive distribution, its zone of occurrence is very linear, and in places fragmented, resulting in a relatively small total area of occupancy. On a global scale, excluding marine species, few turtles even venture into brackish water on a regular basis, and only two Asian species approach the North American terrapin's dependency on estuarine habitats. Here we describe some of the biological and behavioral adaptations of terrapins that allow them to live in the rather harsh estuarine environment. In this chapter we review the natural and cultural history of this turtle, discuss conservation issues, and provide information on the types of research needed to make sound management decisions for terrapin populations in peril.
Article
We evaluated the diets of 81 Carolina diamondback terrapins (Malaclemys terrapin centrata) from northeastern Florida by analyzing fecal samples. Female diets were significantly different from male diets (p < 0.01); fecal samples from females contained crabs, marsh periwinkles (Littorina irrorata), and dwarf surf clams (Mulinia lateralis) in that order of occurrence, whereas fecal samples from males had dwarf surf clams and crabs in that order. We suggest that head-size dimorphism is advantageous to females during nesting forays when they experience a shift in prey availability.
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Hochachka P.W., Somero G.N. (2002) Biochemical adaptation: mechanism and process in physiological evolution. New York: Oxford University Press. 466 p.
Article
Water and salt concentrations in an animal's body fluids can fluctuate with changing environmental conditions, posing osmoregulatory challenges that require behavioral and physiological adjustments. The purpose of this study was to investigate body water dynamics in the estuarine diamondback terrapin (Malaclemys terrapin), a species that undergoes seasonal dormancy in salt marsh habitats. We conducted a field study to determine the total body water (TBW%), water turnover rate (WTR), and daily water flux (DWF) of female terrapins in southeastern North Carolina pre- and post-emergence from winter dormancy. Terrapins were injected with [(2)H]deuterium on two occasions and washout of the isotope was monitored by taking successive blood samples during the period of transition from dormancy to activity. The WTR and DWF of 'dormant' terrapins were significantly lower than those of 'active' terrapins (WTR'dormant'= 49.70 ± 15.94 ml day(-1), WTR'active' = 100.20 ± 20.36 ml day(-1), DWF'dormant'= 10.52 ± 2.92 %TBW day(-1), DWF'active' = 21.84 ± 7.30 %TBW day(-1)). There was no significant difference in TBW% between 'dormant' and 'active' terrapins (75.05 ± 6.19% and 74.54 ± 4.36%, respectively). Results from this field study provides insight into the terrapin's ability to maintain osmotic homeostasis while experiencing shifts in behavioral and environmental conditions.
Article
Mortality of marine vertebrates due to incidental entanglement in fishing gear is of global concern. Trends in diamondback terrapin Malaclemys terrapin abundance and demography suggest that bycatch mortality associated with the blue crab Callinectes sapidus fishery may be contributing to population declines and demographic shifts of this estuarine turtle. Designing effective regulations to minimize terrapin-crabbing interaction requires information on the spatial ecology and seasonal behavior of terrapins. Our goals for this study were (1) to identify spatial and temporal patterns in the distribution of terrapins and crab pots and (2) to determine bycatch risk based on seasonal shifts in terrapin behavior and the degree of overlap between terrapins and crab pots. We documented crab pot locations and monitored the movements and activity patterns of 29 terrapins via radio telemetry in southeastern North Carolina from June 2008 to May 2009. To assess spatial overlap and resulting bycatch risk (BR), we calculated seasonal distributions and densities of crab pots and terrapins and incorporated them into a spatial overlap index model (SOI) modified to include the seasonal aquatic behavior of terrapins. Spatial overlap is greatest in warm months when terrapins are swimming in the same shallow, near-shore habitat as blue crabs. When the seasonal and semi-aquatic behavior of terrapins is incorporated into the spatial model, BR is reduced. This behaviorally modified SOI model may be applied to other geographic areas to identify areas and times of bycatch risk between fisheries and non-target species.
Article
SYNOPSIS. Biochemical adaptation to environmental parameters such as temperature appears to involve two distinct types of changes in the organism's chemistry. On the one hand, the quantities of certain molecular species present in the cells may change. Alternatively, the actual types of molecules present may vary. Rainbow trout (Salmo gairdneri) acclimated to warm and cold temperatures exhibit a striking example of this latter type of adaptation. For all enzymes we have examined in this species, distinct "warm" and "cold" isozymes are present. The isozymes found in warmacclimated (18°C) trout function well only at temperatures above 10-12°C. The isozymes present in cold-acclimated (4°C) trout function optimally at 2-5°C, temperatures this species normally encounters in winter. These data, plus information on comparable changes in membrane lipids, lead us to propose that adult poikilotherms may undergo a considerable degree of "biochemical restructuring" on a seasonal basis. The factors which control this "restructuring," and the rates at which the process occurs at high and low temperatures, are topics for future investigation.
Article
SUMMARY Survival and blood acid-base status were measured on freshwater turtles (Chrysemys picta bellii Gray) that were submerged at 3 °C in either aerated (high Oj) or N2-equilibrated (low O2) water. Results from catheterized turtles, without access to air under these conditions, and from non- catheterized turtles which were either apnoeic (in high O2 and low O2 water) or in high O2 water with access to air, are compared. Under the most adverse conditions (catheterized, submerged, low O2), survival duration was 126± 14 (^T±s.E.) days, and 2 of the 10 turtles so treated were still alive after 177 days, although their condition was poor. Apnoeic, high O2 turtles generally survived longer and were in better condition despite a skin fungus condition that selectively affected these animals. Six of ten non-catheterized high Oa turtles were still alive after 189 days without breathing. All apnoeic turtles developed an acidosis which, except for a transient hypercapnia in low O2 turtles, was a metabolic acidosis attributable to elevated lactic acid. Acidosis was most severe in low O2 turtles in which peak plasma lactates exceeded 200 IBM. High O2 turtles, as judged by higher blood POt and lower lactate concentrations, were able to extract dissolved O2 from the water and support a significant portion of their metabolic requirements by aerobic metabolism. Our data indicate that wintering turtles can remain alive for up to 6 months, even while totally anoxic and severely acidotic, but that the acid-base state and probably the recovery potential are significantly improved if dissolved O2 is available for extra- pulmonary uptake.
Article
Salinity is hypothesized to be the major abiotic factor limiting the colonization of Florida Bay by estuarine reptiles, This premise is supported by the small number of species of reptiles found in the bay in comparison with fresh water, the distinct osmoregulatory specializations of the few estuarine specialists that occur there, and a remarkable cline in the ability to tolerate sea water found among modem-day estuarine and coastal reptiles. This latter cline in osmoregulatory abilities is believed to represent a model of the evolutionary stages through which pelagic snakes and turtles have passed in developing adaptations for life in the open sea. Florida Bay is an especially useful site for the study of such adaptations since it is the only known location in this hemisphere where three specialized estuarine reptiles are sympatrie: the American crocodile (Crocodylus aculus), the diamondback terrapin (Malaclemys terrapin), and the mangrove snake (Nerodia clarkii compressicauda). Small populations of freshwater turtles and the alligator also occur in tidal creeks along the northern shore. Recent advances in the study of turtles suggest that the single most important factor in determining tolerance to high salinity is the amount of sea water swallowed incidentally with food ingestion. This finding needs to be extended to other reptiles to test the hypothesis that fish eaters (such as snakes) that do not crush or bite chunks from their food have reduced incidental drinking. This could explain how the mangrove snake can survive in estuaries without a salt gland, whereas the sympatric terrapin possesses a sizeable lachrymal salt gland. We hypothesize that the following represent major transitional stages in the gradual evolution of marine snakes and turtles from freshwater ancestors: (1) utilization of behavioral osmoregulation to avoid salinities that cannot be directly tolerated; (2) a reduction in net salt uptake and water loss and in incidental drinking of sea water while feeding; (3) the first appearance of rudimentary salt-excreting glands; (4) hypertrophy of salt glands as dictated by rates of salt uptake, in concert with the development of a specialized external morphology suited for a pelagic life.
Article
Thermal preference of free-living yellow-margined box turtle, Cuora flavomarginata, was studied in a mesic forested habitat using a combination of radiotransmitters and temperature dataloggers attached to individual turtles. Patterns of mean weekly shell surface temperature variation of selected individuals were highly related to seasonal change of environmental temperature, with a peak temperature of 24.5-25.1°C in males and 26.0-27.0°C in females during June and July. Minimum shell surface temperature occurred in late January (4.5-7.6°C). Despite a small sample size, there were significantly intersexual differences in mean weekly shell surface temperature during nesting season. Individual females of C. flavomarginata tended to maintain higher shell surface temperature during nesting season (May-July). This difference was mostly pronounced during the day. There were no obviously intersexual differences prior to and after nesting season. Our results do not support the previous predictions that gravid C. flavomarginata may select higher environmental temperatures prior to nesting season.
Article
We should like to thank the Director and Staff of the Laboratory of the Marine Biological Association for their assistance. R. A. McC. has held a part-time grant and H. L. S. a full time grant from the Medical Research Council during this work.
Article
Summary1. Freshwater fishes are the most northerly of freshwater ectotherms, followed by frogs. North American freshwater snakes, turtles, and salamanders do not range farther north than southernmost Canada.2. Freezing and desiccation are the main challenges during terrestrial hibernation of ectotherms. Oxygen depletion, water balance, and ionic balance are the major problems for air breathing ectotherms that hibernate underwater.3. The importance of accumulation of energy stores for overwintering among fishes depends upon the length and severity of the winters, whether or not there is springtime reproduction, body size, latitude, and the availability and use of food during overwintering.4. Fishes can decrease energy demands during the winter by reductions in activity, metabolic depression, and entrance in semi-torpidity.5. Adaptations for coping with hypoxia and anoxia among overwintering freshwater fishes may include metabolic depression, a decrease in blood O2 affinity, microhabitat selection, air breathing, short-distance migration, biochemical modifications aimed at adjusting glycolytic rates, and alcoholic fermentation.6. Freshwater turtles have a worldwide northern limit of approximately 50° N, which means that some species spend about half of their lives hibernating.7. Aquatic turtles normally hibernate underwater, although occasionally they hibernate on land. In water they usually hibernate in a hypoxic or anoxic (mud) environment and in relatively shallow water. Wintertime movements of unknown frequency occur in some species.8. The hatchlings of many turtle species can overwinter in the nest. Among northern species this behaviour is most common among painted turtles, whose hatchlings can withstand freezing.9. Mortality among adult turtles is probably highest during the hibernation cycle.10. Temperature appears to the most important cue for entry and exit from hibernation among freshwater turtles.11. Little is known of the energetics of overwintering turtles. Energy stores for overwintering may be more important at lower latitudes than at higher ones, due to the higher metabolic rates of overwintering, but non-feeding, southern turtles.12. The ability of turtles to tolerate submergence is a function of temperature, degree of water oxygenation, latitude of origin, efficacy of extrapulmonary respiratory pathways, and metabolic rate.13. For turtles that hibernate in an anoxic hibernaculum, and for those without sufficient extrapulmonary uptake of O2 to allow metabolism to be completely aerobic, the most important physiological perturbation is an acidosis developed from a continuing production of lactate. If sufficient O2 can be obtained, the most likely factors limiting hibernation time are water balance and ion balance.14. Mechanisms of turtles for coping with acidosis include metabolic depression, integumental CO2 loss, bicarbonate buffering, and changes in ion concentrations that minimize the decrease in SID (strong ion difference). The most important among the latter are a decrease in plasma [Cl-] and large increases in plasma calcium and magnesium.15. Turtles are unique among reptiles in their ability to maintain both cardiovascular and nervous system function during prolonged anoxia.16. Turtles gain weight from water uptake during submerged hibernation, but apparently maintain some kidney function; however, osmoregulation is one of the least known areas of the physiology of hibernation.17. Recovery of turtles upon emergence commences with a rapid hyperventilatory compensation of pH, followed by a slower adjustment of ion levels. Basking speeds recovery greatly.18. While hibernation of turtles in the northern parts of their ranges is most likely very stressful physiologically, northern range limits are more likely to be determined by reproductive restraints than by the rigors of extended hibernation.19. The superior ability of turtles to tolerate anoxia may be more the result of an annual hibernation than of their diving habits during active periods of the year.20. Freshwater snakes usually hibernate on land. However, they appear to be capable of aquatic hibernation and may not do so because of the risk of death from anoxia.21. Some species of terrestrial snakes are known to hibernate underwater, and are able to do so in the laboratory for months. In the field, this behaviour is considered opportunistic, as there is no evidence to suggest that any snakes can tolerate extended anoxia.
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Information theory and log-likelihood models - a basis for model selection and inference practical use of the information theoretic approach model selection uncertainty with examples Monte Carlo insights and extended examples statistical theory.
Article
Diamond terrapins, Malaclemys terrapin Latreille, inhabit salt marshes and estuaries where they may encounter sustained high salinities for weeks or months. Terrapins can discriminate between salinities. When salt-loaded they avoid drinking high salinities (27.2–34.0%), drink small amounts of salinities which are a little more concentrated than the blood (13.6–20%), and drink copious quantities of lower salinities (0–10.2%). After seven days in full sea water (34%) they can rehydrate themselves in < 15 min if given access to fresh water. Terrapins are capable of drinking from the thinnest of freshwater films (1.6 mm), exploit menisci and have specific postural responses to collect small quantities of fresh water from horizontal and vertical surfaces. Specimens of Malaclemys terrapin respond to the vibration of simulated rainfall by rapid emergence followed by drinking from thin films, either on the exposed substratum or from the surface of the water column. Under simulated conditions of heavy rainfall they collect rain directly from above.
Article
Postural and kinematic characteristics of the drinking behaviour in the diamondback turtle, Malaclemys terrapin (Latreille) were investigated by video and high-speed filming experiments. Head, jaw and throat movements in drinking cycles are described. Postures of neck and head were compared for three water depths (2, 10 and 30 mm). Water expulsion, occurring after the turtle was disturbed, is also kinematically described. Finally, a drinking mechanism in the turtle is proposed.
Article
The estuarine turtle,Malaclemys terrapin is able to ionregulate when acclimated to fresh water, 55% sea water or 100% (full strength) sea water, but when in 100% sea water it does not volume regulate successfully. Orbital gland secretions collected by a new eye cup method are very low in animals from all three salinities without salt load. After salt loading the animals from all three groups produce an orbital gland secretion with a sodium concentration greater than sea water. The concentration of ions and kinetics of the response are similar in all three groups. Orbital gland secretion returns to control preload levels well before the injected load is excreted. There is no correlation between the plasma sodium concentration and any of the parameters of the orbital gland response. There is also no correlation between the concentration of sodium in the tear fluid or the rate of sodium excretion and the level of K+-stimulatedp-nitrophenylphosphatase activity in the gland. Some of these unexpected results may relate to the estuarine habitat occupied byMalaclemys.
Article
Total body water decreased significantly in terrapins exposed to sea water (SW). Although the intracellular fluid decreased somewhat upon SW exposure, the decline in extracellular fluid was almost twice as great. Under conditions of voluntary drinking after salt loading, terrapins substantially increased the volume of the extracellular fluid while maintaining the intracellular fluid near the freshwater (FW) control levels. FW terrapins were consistently heavier than animals of the same plastron length exposed to SW. Thus expression of body fluid volumes as ml/cm plastron length rather than as % body weight is necessary to correct for the loss of total body water with progressive dehydration. Fasted terrapins in SW lost weight at 0.32% weight/day, whereas the rate in FW was 0.21%/day. Water influx and efflux in SW were 0.17 and 0.16 ml/100 gh respectively. When the efflux was increased by the calculated value for unmeasured respiratory loss, it exceeded the influex by 0.01 ml/100 gh. Consequently the net water loss determined with radiotracers (equivalent to 0.24% weight/day) was similar to the difference between the weight losses in SW and FW (0.11%/day). Partitioning studies indicated that the majority of water exchange between the terrapin and SW occurs through the integument. Terrapins in SW underwent a concentration of the body fluids, most of which can be attributed to water loss, not electrolyte gain. The rates of Na influx and efflux were quite low (usually ranging from 6–10 moles/100 gh). In two terrapins the injection of NaCl loads resulted in eight- to 19-fold increases in Na efflux. The uptake of Na from SW occurred orally. The skin was virtually impermeable to Na. The salt gland and possibly the cloaca were the major routes of Na efflux. The injection of NaCl loads resulted in an increase in cephalic Na excretion from a mean of 3.2 moles/100 gh to 32.5 moles/100 gh. Terrapins in SW exhibited a significant increase in bladder urine [K] over the FW controls. There was a direct relationship between plasma [Na], urine [K], and lachrymal salt gland Na–K ATPase content. In comparing SW terrapins with FW painted turtles (Chrysemys) exposed to SW radiotracer studies demonstrated a similarity in Na influx, but there was at least a four-fold increase in water exchange in the painted turtle. It seems likely that the skins of many aquatic reptiles (marine, estuarine and FW) are impermeable to Na but differ markedly in water permeability.
Article
Patterns of tolerance to stressful abiotic variables among animals that have colonized salt marshes provide models for the study of the evolution of physiological specialization. We provide an overview of some closely related pairs or groups of species that show hierarchical gradations in tolerance, and thereby physiological mechanisms of compensation, along a line perpendicular to the shore. However, a full understanding of the evolution of physiological specialization requires that we evaluate the role of abiotic factors in light of the biotic interactions in which salt-marsh species are embedded. The common occurrence of salt-marsh endemics in a species-poor environment must be related to the unusual character of this habitat, in which the reduced importance of some biotic forces is paired with highly stressful abiotic factors. The salt marsh is probably not a refuge for competitively inferior forms so much as it is a highly selective environment that admits only those specialized species that can muster the necessary physiological adaptations. Thus the apparently lower competitive ability of salt-marsh species under conditions that are not abiotically stressful is likely to be a secondary consequence of the costs of mechanisms conferring tolerance, and of life in a species-poor habitat. Salt marshes provide an arena in which it is possible to experimentally evaluate the evolutionary and ecological importance of abiotic stress, especially in relation to parapatric or allotopic distributions. Yet very few studies have provided such a rigorous approach, despite a long-standing recognition that abiotic factors interact strongly with biotic forces in the salt marsh.
Article
Herbivore damage is generally detrimental to plant fitness, and the evolu- tionary response of plant populations to damage can involve either increased resistance or increased tolerance. While characters that contribute to resistance, such as secondary chem- icals and trichomes, are relatively well understood, characters that contribute to a plant's ability to tolerate damage have received much less attention. Using Helianthus annuus (wild sunflower) and simulated damage of Haplorhynchites aeneus (head-clipping weevil) as a model system, we examined morphological characters and developmental processes that contribute to compensatory ability. We performed a factorial experiment that included three levels of damage (none, the first two, or the first four inflorescences were clipped with scissors) and eight sires each mated to four dams. We found that plants compensated fully for simulated head-clipper damage and that there was no variation among plant families in compensatory ability: seed production and mean seed mass did not vary among treat- ments, and sire X treatment interactions were not significant. Plants used four mechanisms to compensate for damage: (1) Clipped plants produced significantly more inflorescences than unclipped plants. Plants produced these additional inflorescences on higher order branches at the end of the flowering season. (2) Clipped plants filled significantly more seeds in their remaining heads than did unclipped plants. (3) Clipped plants, because they effectively flowered later than unclipped plants, were less susceptible to damage by seed- feeding herbivores other than Haplorhynchites. (4) In later heads, seed size was greater on clipped plants, which allowed mean seed size to be maintained in clipped plants. Although there was genetic variation among the families used in this experiment for most of the characters associated with compensation for damage (seed number, mean seed size, mean flowering date, length of the flowering period, and branching morphology), in analyses of these characters, no sire X treatment interactions were significant indicating that all of the families relied on similar mechanisms to compensate for damage.
Article
Diamondback terrapins (Malaclemys terrapin) are thought to be declining throughout their range. Although many factors have been proposed to contribute to terrapin declines, including increased predation of nests and adults, habitat loss and degradation, road mortality, commercial harvest for food, and mortality as bycatch in crab traps, few studies have provided evidence linking these agents to population declines. Because male and small female terrapins are most susceptible to mortality in crab traps, population declines should coincide with shifts in the age and size distributions of the population and a shift to a more female-biased sex ratio. We used twenty-one years of mark-recapture data (>2800 captures of 1399 individuals) from a declining diamondback terrapin population in South Carolina to test the prediction that the decline is the result of mortality in crab traps. Since the 1980s, the modal size of both male and female terrapins has increased substantially and the proportion that are females is higher than in earlier samples. Additionally, the population now contains more old and fewer young individuals than before. The changes in demography and sex ratio we observed suggest that this terrapin population has declined as a result of selective mortality of smaller individuals in crab traps. The use of bycatch-reduction devices on crab traps may help prevent terrapins from entering the traps, but current models are too large to prevent mortality of males and many females in this population. Future research should focus on design and testing of effective bycatch-reduction devices for specific regions and other methods to prevent terrapin mortality in crab traps.
Article
1.1. Diamondback terrapins (Malaclemys terrapin) were caught in the wild at salinities between 11·3 and 31·8%.2.2. Acclimation of terrapins to sea water caused a 2·4-fold increasein the Na concentration of orbital fluid. Two species of crocodiles (Crocodylus acutus, C. porosus) showed only a 1·4-fold increase.3.3. Sea water acclimation in terrapins caused a rise in plasma Na concentration. The increase was relatively small over a 6-week period of acclimation. Wild-caught terrapins had a higher plasma Na concentration.4.4. Maximum rates of salt gland secretion in sea water-acclimated terrapins measured by a head rinse technique varied from 16·8 to 26·6 μmoles Na/100 g hr. In fresh-water-acclimated animals secretion was less than 1 μmole Na/100 g hr. The estuarine terrapin thus has a salt gland intermediate in secretory capacity between those of terrestrial and marine reptiles.5.5. Preliminary evidence provides little support for the concept that American and “salt water” crocodiles utilize salt glands as a major pathway of electrolyte excretion, although these crocodiles are fairly tolerant of exposure to sea water.
The amounts of energy liberating substrates in muscle, heart, liver and total carcass were determined in painted turtles just prior to (early October) and upon arousal from (late March) hibernation. Between the fall and spring samples, total carcass neutral lipids, protein and glycogen were depleted 37.8%, 11.0% and 70.2%, respectively. Total carcass lactate increased 551% in post-hibernatory turtles suggesting an important role for anaerobic glycolysis in producing energy during periods of anoxia. Females used more energy than males; however, the pattern of substrate utilization was similar in both sexes with lipid, protein and glycogen providing 56%, 27% and 17% of the energy, respectively.
Article
Many organisms endure extended periods of dormancy by depressing their metabolism, which effectively prolongs the use of their endogenous energy stores. Though the mechanisms of hypometabolism are varied and incompletely understood, recent work suggests that urea accumulation in autumn and early winter contributes to reduced metabolism of hibernating wood frogs (Rana sylvatica). Urea accumulation during dormancy is a widespread phenomenon, and it has long been presumed that numerous species from diverse taxa benefit from its hypometabolic effect. To investigate the phylogenetic prevalence of urea-induced hypometabolism, we studied four species of urea accumulators from the clades Amphibia (Spea bombifrons and Ambystoma tigrinum), Reptilia (Malaclemys terrapin), and Gastropoda (Anguispira alternata), and one amphibian species (R. pipiens) that does not accumulate urea during dormancy. We measured rates of oxygen consumption (VO(2)) of excised organ samples from dormant animals in the presence or absence of physiological concentrations of urea. Three of the four urea-accumulating species had at least one organ whose VO(2) was significantly decreased by urea treatment. However, VO(2) of organs from R. pipiens, the one species tested that does not accumulate urea during dormancy, was not affected by urea treatment. Our results support the hypothesis that urea accumulation can reduce metabolic rate of dormant animals and provide a base for further investigation into the evolution of urea-induced hypometabolism.
Article
1. It is widely accepted that reptiles are able to regulate behaviourally their body temperature (T(b)), but this generalization is primarily based on studies of lizards and snakes in the temperate zone. Because the precision of T(b) regulation may vary considerably between taxa and over geographical ranges, studies of semi-terrestrial turtles in climatic extremes are relevant to the understanding of reptilian thermoregulation. 2. We studied thermoregulation in 21 free-ranging wood turtles (Glyptemys insculpta) at the northern limit of their range in Québec, using miniature data loggers to measure their internal T(b) and external temperature (T(ext)) continuously. We simultaneously recorded the available operative environmental temperature (T(e)) using 23 physical models randomly moved within each habitat type, and we located turtles using radiotelemetry. 3. The habitat used by wood turtles was thermally constraining and the target temperature (T(set)) was only achievable by basking during a short 5-h time window on sunny days. Wood turtles did show thermoregulatory abilities, as determined by the difference between turtle T(b) distribution and the null distribution of T(e) that resulted in T(b) closer to T(set). Although most individuals regulated their T(b) between 09.00 h and 16.00 h on sunny days, regulation was imprecise, as indicated by an index of thermoregulation precision (| T(b) - T(set) |). 4. The comparison of habitat use to availability indicated selection of open habitats. The hourly mean shuttling index (| T(ext) - T(b) |) suggested that turtles used sun/shade shuttling from 09.00 to 16.00 h to elevate their T(b) above mean T(e). 5. Based on laboratory respirometry data, turtles increased their metabolic rate by 20-26% over thermoconformity, and thus likely increased their energy gain which is assumed to be constrained by processing rate at climatic extremes.
Article
To compare blood biochemical values obtained from a handheld analyzer, 2 tabletop analyzers, and 2 diagnostic laboratories by use of replicate samples of sea turtle blood. Validation study. 22 captive juvenile sea turtles. Sea turtles (18 loggerhead turtles [Caretta caretta], 3 green turtles [Chelonia mydas], and 1 Kemp's ridley turtle [Lepidochelys kempii]) were manually restrained, and a single blood sample was obtained from each turtle and divided for analysis by use of the 5 analyzers. Hematocrit and concentrations or activities of aspartate aminotransferase, creatine kinase, glucose, total protein, albumin, BUN, uric acid, P, Ca, K, Na, Cl, lactate dehydrogenase, and alkaline phosphatase were determined. Median values for each analyte were compared among the analyzers. Significant differences were found among the analyzers for most values; however, data obtained from the 2 diagnostic laboratories were similar for all analytes. The magnitude of difference between the diagnostic laboratories and in-house units was > or = 10% for 10 of the 15 analytes. Variance in the results could be attributed in part to differences in analyzer methodology. It is important to identify the specific methodology used when reporting and interpreting biochemical data. Depending on the variable and specific case, this magnitude of difference could conceivably influence patient management.