Robert W. Putnam

Thermal Dependence of Behavioural Performance of Anuran Amphibians

The thermal dependence of performance capacity was assessed in two anuran amphibians: Bufo boreas (western toad) and Rana pipiens (leopard frog). Quantitative measurements of performance showed that Bufo could sustain slow rates of walking for 10 min and cover greater distances than Rana, which initially jumped more vigorously but fatigued within 5 min. Changes in performance with changes in body temperature were virtually instantaneous, and performance exhibited no acclimation over 7 days. Within the range of temperatures studied, performance capacity increased with increasing body temperature and reached a maximum at 28 C in Bufo and 20 to 29 C in Rana. Performance capacity and the underlying metabolic processes had a similar thermal dependence within a species. The behavioural capacity for activity is apparently maximal for both species at body temperatures normally encountered in the field. Anuran behaviours requiring sustained activity (migration to breeding sites, mating, foraging) must therefore be markedly temperature-sensitive.

Water, Nitrogen and Ion Balance in the African Treefrog Chiromantis petersi Boulenger (Anura: Rhacophoridae), With Comments on the Structure of the Integument

SummaryPhysiological and anatomical investigations were carried out onChiromantis 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.

Thermal Dependence of Isometric Contractile Properties of Lizard Muscle

Summary1.The thermal dependence of the isometric contractile properties of the iliofibularis and gastrocnemius muscles were studied at 5°C intervals from 10–50°C in lizards with different preferred body temperatures (PBT):Dipsosaurus dorsalis (PBT: 40–42°C);Cnemidophorus murinus (40°C);Sceloporus occidentalis (35°C); andGerrhonotus multicarinatus (25–30°C).2.Isometric twitch and tetanic tensions were constant over a broad temperature range (as much as 25°C) in all species. Tetanic tension declined by 50% at 45–47.5°C inDipsosaurus, 42.5°C inCnemidophorus, and 40°C inSceloporus andGerrhonotus.3.Twitch contraction time (CT-the time to the peak twitch tension) increased with decreasing temperature from 10 ms to 300 ms. At any given temperature, the muscles ofSceloporus andGerrhonotus had faster CTs than those of the other species. The CTs were minimal at the maximal test temperature.4.The maximal rate of tension development with tetanic stimulation (dPo/dt) was strongly temperature dependent and was maximal at 40–45°C inDipsosaurus, 40–42.5°C inCnemidophorus, and 35°C inSceloporus andGerrhonotus.5.The time properties of these muscles are highly temperature dependent and contractile tensions are broadly temperature independent. Except inGerrhonotus muscles, the combination of twitch speed and tension generating capability is maximal at PBT, although neither parameter alone is maximized at PBT.

The Basis for Differences in Lactic Acid Content after Activity in Different Species of Anuran Amphibians

The basis for differences in whole-body lactic acid concentrations after activity in three species of anurans was investigated. Rana pipiens and Xenopus laevis were exercised to fatigue, and Bufo boreas were kept in continuous activity for 15 min. Differences exist among the species in the ratio of muscle to body mass in the order X. laevis > R. pipiens > B. boreas. Whole-animal and hind-limb-muscle lactic acid concentrations after activity varied among species in the following order: X. laevis > R. pipiens > B. boreas. Lactic acid concentrations were similar in the sartorius muscles of the three species, but B. boreas differed from the other two species in the concentrations of lactic acid in its gastrocnemius muscles. Blood lactic acid was high in all three species, 140-200 mg/100 ml, led to a decrease in blood pH to around 7.0, and was a poor indicator of whole-body lactic acid. A total lactic acid budget for each species based on muscle, blood, and liver compartments was constructed and accounted for 75% of the whole-animal lactic acid after activity. The remainder is presumably due to diffusion of lactic acid into other body compartments. It is suggested that differences in whole-animal lactic acid in active anurans can be explained by differences in the involvement of muscle groups during activity, by the fraction of the body mass composed of muscle, and by differences in the accumulation of lactic acid in specific muscles in different species.

Thermal Environment and Tolerance of Embryonic Western Gulls

The thermal environment and tolerance of eggs and embryos of western gulls (Larus occidentalis wymani) on San Nicolas Island, California, were determined. Incubated egg temperature measured by telemetry ranged between 30 and 36 C and averaged 33.4 and 34.2 C for two different nests; the former underwent pronounced cycles of heating during the day and cooling at night. Exposed eggs underwent a daily thermal excursion between 6 and 50 C. Embryos could maintain heartbeat between 11 and 46 C. Eggs which are exposed to solar radiation heat slowly (about 5 C/h). Diurnal exposure during parental absence does not, therefore, result in embryonic mortality unless exposure persists for several hours. Embryos recover completely after overnight exposure to relatively cool temperatures. Short-term exposure does not, therefore, constitute an immediate threat to embryonic survival. Adult gulls in this colony do not closely defend their nests and will leave them exposed in the presence of an intruder. The behavior of the parent gull and physiological tolerance of the embryos in reference to the thermal environment form an adaptive suite of characters contrasting with those of other gulls nesting under hot and arid conditions.

Hematological Parameters of Five Species of Marine Fishes

Abstract 1. 1. Blood oxygen capacity (BOC). hemoglobin (Hb) content, hematocrit (Hct). red blood cell (RBC) count, and pH were measured in five species of marine fishes which varied in activity from sedentary to fast swimming. 2. 2. BOC and Hb content were correlated with the level of activity for a species. RBC and Hct varied between species and were more weakly correlated with levels of activity. Blood pH did not vary between the species studied. 3. 3. These data suggest that increased BOC is correlated with high levels of activity in fish and that this increase is due to elevated Hb content of the blood. The increased Hb is generally accompanied by an increase in RBC count, so that the average corpuscular hemoglobin (ACH) remains the same.

Low metabolic rate in a nocturnal desert lizard, an arbylus switaki murphy (Sauria: Gekkonidae)

Abstract 1. 1. Metabolic rates were measured in two xeric-adapted gekkonid lizards, Anarbylus switaki sind Coleonyx variegatus . 2. 2. Standard metabolic rates (SMR) were 0.074 ml O 2 /g hr in A. switaki and were 70% of the value predicted on the basis of mass from regression equations. The SMR of 0.146ml O 2 /ghr in C. variegatus is similar to the predicted value for a lizard of this mass. 3. 3. During intense activity, metabolic rates of 0.378 and 0.804ml O 2 /g hr were measured in A. switaki and C. variegatus , respectively. 4. 4. Various theories to explain reduced SMR in lizards are discussed, and it is concluded that none is entirely satisfactory, and caution should be exercised in interpreting the adaptive significance of reduced SMR.