Edward A. Standora

Operative environmental temperatures and basking behavior of the turtle Pseudemys scripta

Operative environmental temperatures (T/sub e/, an index of the thermal environment) were measured for basking Pseudemys scripta in South Carolina. Operative environmental temperatures were good predictors of the basking behavior of P. scripta. Turtles in this study generally did not bask unless T/sub e/ was 28/sup 0/C (preferred body temperature) or higher. This demonstrated that basking was not a random behavior in respect to T/sub e/, and implicated thermoregulation as a major factor eliciting basking behavior. Operative environmental temperature was positively related to short-wave and total solar radiation as well as to air and substrate temperature. Substrate temperature was the best single predictor of T/sub e/. A multiple regression equation (T/sub e/ = 0.005R + 0.103T/sub a/ - 1.16 log V + 0.932T/sub s/ - 2.54, r/sup 2/ = .90, where R = total radiation in watts per square metre, T/sub a/ = air temperature in degrees Celsius, V = wind speed in metres per second, and T/sub s/ = substrate temperature in degrees Celsius) defines the relationship of T/sub e/ to microclimate variables. Movement of the sun through the day results in spatial variation in T/sub e/s available to turtles and influences their location and basking behavior.

Roles of Diet Protein and Temperature in the Growth and Nutritional Energetics of Juvenile Slider Turtles, Trachemys scripta

We determined the effects of dietary protein and Ta on growth rates, food consumption rates, digestion rates, and digestive efficiencies of juvenile slider turtles (Trachemys scripta). Results from this study provide a clearer understanding of how these environmental factors interact in influencing body sizes and growth rates of individuals in wild slider turtle populations. Changes in plastron length, carapace length, and body mass were significantly greater for T. scripta eating 25% and 40% crude protein diets than for those eating 10% crude protein. Those consuming 10% crude protein showed significant decreases in body mass and plastron length over a 13-wk period. Individuals at Tas of 15°, 22°, 28°, or 34° C had food ingestion rates (kJ wk⁻¹) that increased markedly with an increase in Ta. Increasing dietary crude protein concentration increased turtle ingestion rates and influenced the positive effect of Ta. Increasing dietary crude protein concentration alone did not significantly affect turtle consumption rates but did significantly influence the positive effect of Ta. Digestive efficiencies were very high (because of the pelleted diet). Those turtles that ate at 15° C had a digestive efciency of 99.5%, as compared with 98.3% at 22° C, 94.8% at 28° C, and 95.8% at 34° C. Dietary protein concentration did not influence the digestive efficiencies of T. scripta. These data suggest that dietary protein is an important nutritional component to the growth of juvenile slider turtles and that elevated thermal conditions, combined with a high dietary protein availability, may explain the very high growth rates of slider turtles in some wild populations.

Growth selected temperature and CTM of young snapping turtles, Chelydra serpentina

Abstract 1. 1.Snapping turtle hatchings raised at 25°C ate freely and grew from 7.4 to 50.7 g in 1 year, while those at 15°C ate little and did not grow. 2. 2.Selected body temperature in a terrestrial gradient were similar for 15 and 25°C in fall/winter and spring (if X =24.6° C ). In spring, turtles from 15 and 25°C had similar selected temperatures in an aquatic temperature gradient (if X =28.0° C ). 3. 3.The CTM of 25°C turtle was significantly higher ((if X =41.1° C ) than that of 15°C turtles (if X =39.1° C ). We transferred the 15°C turtles to 25°C and the 25°C to 15°C. After 1 week the CTMs were the same. When transferred for 3 weeks, 15–25°C turtles had a significant higher CTM (if X =41.4° C ) than 25-15°C turtles (if X =39.6° C ). 4. 4.Thus, the CTM is directly related to acclimation temperature but selected temperature is independent of acclimation temperature, growth rate and age.

Environmental Constraints on the Thermal Energetics of Sea Turtles

The thermal biology of sea turtles depends upon the heat transfer properties of their environment as well as the physical and physiological characteristics of the turtles. In water, heat loss predominates over heat gain but on land, lethal heat gain during the day is one factor that selects for nocturnal nesting activity. Small turtles, Lepidochelys sp. and Eretmochelys imbricata, can nest during the day, if exposed to wind, because they are less affected by solar radiation than larger species since they lose more heat via convection. Sea turtles employ both behavioral and physiological thermoregulation. Loggerheads, Caretta caretta, can raise body temperatures (Tb) 3.8 C above ocean temperatures by basking in water and green turtles, Chelonia mydas, can elevate Tb 5 C above ocean temperatures by basking on land. Large turtles are endothermic. Green turtles exhibit regional endothermy, with active tissues 8 C above ocean temperatures during vigorous swimming. Leatherback turtles, Dermochelys coriacea, have body temperatures as much as 18 C above an ambient water temperature of 7.5 C. Multichannel telemetry demonstrates that the internal temperatures of a resting leatherback are higher than carapace and ambient air temperatures indicating that heat is generated internally and not absorbed from the environment.

Regional endothermy in the sea turtle, Chelonia mydas

Abstract 1. 1.|The green turtle, Chelonia mydas , exhibits a unique combination of thermoregulatory adaptations. Temperature data obtained by mutlichannel telemetry indicate that it is a regional endotherm. 2. 2.|A turtle swimming vigorously had a body temperature (pectoral region) of 37.1°C in water at 29.1°C. Inactive adults are 1–2°C above water temperatures. 3. 3.|Temperatures telemetered from other parts of the body of swimming turtles and temperatures of resting individuals suggest that only the active tissues, and not the entire body, are at an elevated temperature. 4. 4.|Heat is retained in the active tissues due to large body size and insulatory properties of the shell. 5. 5.|Warm pectoral muscles (7°C above water temprature) probably increase this turtles swimming ability and may facilitate its long-distance migrations.

Bioenergetics, Behavior, and Resource Partitioning in Stressed Habitats: Biophysical and Molecular Approaches

Studies of the biophysical and molecular adaptations of turtles, fish, and salamanders in stressed habitats have allowed us to determine various aspects of their fundamental physiological niches. Mathematical modeling of the climate requirements of Trachemys scripta and field studies at the Savannah River Plant indicate that thermal conditions and diet quality affect the behavior and bioenergetics of this turtle, and ultimately its life-history pattern. Mathematical modeling and laboratory and field studies indicate that the thermoregulatory behavior of largemouth bass, Micropterus salmoides, interacts with competition and predation to affect the population dynamics of this fish. Experiments on whole-animal thermal tolerance and heat-shock proteins of two salamander species indicate that differences in the microhabitat selection and geographic ranges of Eurycea bislineata and Desmognathus ochrophaeus are related to differences in their thermal biology.

Peripheral circulation inAlligator mississippiensis effects of diving, fear, movement, investigator activities, and temperature

Summary1.Cutaneous and skeletal muscle blood flows cease when alligators are forcibly submerged or when they are disturbed by the investigator. Contrary to previous reports, blood flow to the musculature and tail of freely diving alligators remains normal during submergence, as measured with133Xe (Fig. 2). Cardiovascular adjustments previously reported for diving reptiles appear to be due largely to a psychogenic response (fear) induced by experimental manipulation.2.Handling and experimental manipulation cause a statistically significant elevation in peripheral blood flow at the beginning of an experiment. Blood flow then gradually decreases and reaches a steady-state after 30 min. Muscles and skin are minimally perfused when at rest. Standard blood flows for muscle ranged from 0.004 to 0.049 ml·g−1 min−1

Behavioural thermoregulation of largemouth bass (Micropterus salmoides): response of naive fish to the thermal gradient in a nuclear reactor cooling reservoir

(\bar X = 0.018)