Factors affecting body temperatures of toads

Factors influencing levels and rates of variation of body temperature ( T b ) in montane Bufo boreas boreas and in lowland Bufo boreas halophilus were investigated as an initial step toward understanding the role of natural thermal variation in the physiology and energetics of these ectothermic animals. Body temperatures of boreas can vary 25–30° C over 24-h periods. Such variation is primarily due to both nocturnal and diurnal activity and the physical characteristics of the montane environment. Bufo boreas halophilus are primarily nocturnal except during breeding and are voluntarily active at body temperatures ranging between 10 and 25° C. Despite variation in T b encountered in the field, boreas select a narrow range of T b in a thermal gradient, averaging 23.5 and 26.2° C for fasted individuals maintained under field conditions or acclimated to 20° C, respectively. In a thermal gradient the mean T b of fasted halophilus acclimated to 20° C is 23.9° C. Skin color of boreas varies in the field from very dark to light. The dark skins absorb approximately 4% more radiation than the light ones. Light colored boreas should absorb approximately 5% more radiation than similarly colored halophilus . Evaporative water losses increase directly with skin temperatures and vapor pressure deficit in both subspecies. Larger individuals heat and cool more slowly than smaller ones. Calculation of an enery budget for boreal toads suggests that they could sit in direct sunlight for long periods without fatally overheating, providing the skin was continually moist.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47722/1/442_2004_Article_BF00344732.pd

Effects of foraging mode and season on the energetics of the Marine Iguana, Amblyrhynchus cristatus

1, Marine Iguanas (Amblyrhynchus cristatus) inhabiting the rocky shores of the Galapagos Islands apply two foraging strategies, intertidal and subtidal foraging, in a seasonal climate. Effects of both foraging strategy and seasonality on the daily energy expenditure (DEE) were measured using doubly labelled water. 2, Difference in foraging mode did not result in significant differences in DEE. 3, On Santa FC the DEE in the warm season was significantly higher than in the cool season (57.8 +/- 21.8 kJ kg(-0.8) day(-1) vs 38.0 kJ kg(-0.8) day(-1)). This difference can be explained by body temperature. A model estimate of the body temperature was used to predict monthly DEE figures, giving a year round budget. On average a l-kg iguana would need only 47 kJ day(-1), or 17 mJ year(-1). This is lower than previous estimates in which body temperatures were not taken into account. 4, The water flux of the Marine Iguana increases with increasing foraging time. The linear rise per minute foraging is roughly two times as high for subtidally foraging animals as for intertidal foragers

Water, Nitrogen and Ion Balance in the African Treefrog \u3cem\u3eChiromantis petersi\u3c/em\u3e Boulenger (Anura: Rhacophoridae), With Comments on the Structure of the Integument

Physiological and anatomical investigations were carried out on Chiromantis petersi, an African rhacophorid treefrog, with the following results: 1. The minimum rate of evaporative water loss (EWL) was 0.41±0.25 mg/g.h. 2. The maximum rate of water uptake in dehydrated frogs averaged 75% body weight/h in the first 10 min of rehydration. 3. The low EWL correlates with the unique structure of the chromatophore units of the dorsum, the sides and the gular region. 4. The high rates of water uptake correlate with the structure of the verrucae hydrophilica of the abdominal and femoral surfaces. These verrucae are not unique to this species. 5. When denied water and force-fed mealworms for 30 days, plasma osmotic concentrations increased from 210 mosM to 384 mosM, with Na+, Cl− and urea contributing most to the increase. 6. The ratio of urinary K+∶Na+ excretion is 3∶1. 7. Excretion totaled 155 mg N/kg·day with 97% as uric acid, 2% as ammonia and 1% as urea. 8. Since urea accumulated in the body at the rate of 58.5±6.1 mg N/kg·day, total nitrogen production was 213 mg N/kg·day. Uric acid formed 70% thereof. 9. Chiromantis petersi is capable of surviving without free water for prolonged periods and is as well adapted to its xeric environment as are many desert reptiles