Physiological diving adaptations of the australian water skink Sphenomorphus quoyii

• 1.1. Both the small riparian skink Sphenomorphus quoyii and its completely terrestrial relative Ctenotus robustus respond to forced submergence with instantaneous bradycardia.
• 2.2. The strength of the bradycardia was affected by water temperature and fear. Dives into hot (30°C) water produced weak and erratic bradycardia compared to dives into cold (19.5°C) water. For S. quoyii the strongest bradycardia occurred when submergence took place in water at a lower temperature than the pre-dive body temperature.
• 3.3. Upon emergence both species of skink exhibited elevated heart rates and breathing rates while heating from 19.5 to 30°C, compared to heating at rest. The increased heart and breathing rates probably act to replenish depleted oxygen stores and remove any lactate. Increased heart and ventilation rates are not indicators of physiological thermoregulation in this case.
• 4.4. Both lizard species exhibited higher heart rates and ventilation frequencies during heating than cooling.
• 5.5. Compared to its terrestrial relative, S. quoyii does not appear to possess any major thermoregulatory, ventilatory or cardiovascular adaptations to diving. However, very small reptiles may be generally preadapted to use the water to avoid predators.

     

Effects of low environmental pH and temperature on hatching and metabolic rates in embryos of Anax junius drury (Odonata: Aeshnidae) and the role of hypoxia in the hatching process

• 1.1. Studies were conducted in order to determine the combined effects of low environmental pH and temperature on embryonic survival capacity and metabolic rates in the dragonfly, Anax junius Drury. Studies were also conducted to assess the effects of hypoxia on hatching success as well as to investigate the role of hypoxia as a possible physiological triggering mechanism for hatching.
• 2.2. At water temperatures of 10–30°C, an environmental pH value of 3.0 was extremely limiting and significantly reduced hatching success.
• 3.3. Over a pH range of 3.0–5.0, a water temperature of 30°C was found to be severely limiting. Over a pH range of 6.0–7.0, hatching success was greater than 80% at test temperatures ranging from 10 to 25°C.
• 4.4. Embryos of A. junius exhibited a greater tolerance to markedly low environmental pH (3.0) than that previously reported for fish and amphibians, although survival capacity was less than 10%.
• 5.5. An environmental pH value of 3.0 has a significant detrimental effect on embryonic development. Survivorship and developmental rate increase significantly over a pH range of 4.0–5.0.
• 6.6. Oxygen consumption rates were lowest for fertilized eggs exposed to a pH of 3.0 at all test temperatures (10–30°C). Metabolic rates increased significantly at pH 4.O.
• 7.7. Embryos hatch successfully under hypoxic conditions in both aqueous and nonaqueous media. Results suggest that hypoxia acts as a triggering mechanism for hatching in this aquatic insect.

     

The dependence of oxygen consumption of the common whelk (Buccinum undatum) on hypoxia,salinity and air exposure

• 1.1. Oxygen consumption of low salinity (20‰) acclimated whelks decreases markedly upon acute exposure to hypoxia (P_WO₂ = 35 Torr), but almost regenerates its original level within 48 hr exposure to the hypoxic condition.
• 2.2. This ability to regain the original level of oxygen consumption is not seen in high salinity (35‰) acclimated whelks.
• 3.3. Oxygen consumption in air at 10°C is more than twice the rate shown by low salinity acclimated whelks in normoxic water (P_WO₂ = 150 Torr).
• 4.4. Q₁₀ for oxygen consumption in air is about 1.0 in the temperature range 10–20°C.

     

Rates of heat exchange in the ornate box turtle,Terrapene ornata

• 1.1. Eight ornate box turtles, Terrapene ornata, were heated and cooled in water at 35 and 15°C respectively.
• 2.2. Thermal time constants were calculated and no significant differences were found (t-test; 0.05 level) between warming and cooling rates.
• 3.3. Heart-rate data indicated slightly higher, but non-significant, mean values during warming.
• 4.4. It was concluded that T. ornata is not able to physiologically alter rates of heat exchange in water significantly and must rely on behavioral mechanisms to maintain body temperature.

     

Temperature acclimation in respiratory and cytochrome c oxidase activity in common carp (Cyprinus carpio)

• 1.1. Common carp (Cyprinus carpio) exposed to experimental temperatures of 12, 18, 24, 30 or 36°C for a 4-week period were used to investigate the effect of temperature acclimation on the frequency of opercular movement (FOM), growth and cytochrome c oxidase (CCO) activity in heart, liver and muscle.
• 2.2. An exponential relationship between FOM and temperature after the first week (10₁₀ =1.76) disappeared after the second week.
• 3.3. The initially high FOM at temperatures of 30 or 36°C and the low FOM at 18 or 12°C changed over 4 weeks to approach the FOM of fish at 24°C.
• 4.4. This change in the relationship of FOM to temperature from highly dependent to independent appeared to be thermal compensation.
• 5.5. Heart and liver CCO activities were significantly affected by temperature, with the lowest activity at the approximate optimum temperature for growth, 24°C.
• 6.6. Highest CCO activities for heart and liver occurred at both the highest and lowest temperatures.
• 7.7. Among the three tissues, heart CCO activity was generally the highest and most affected by acclimation temperature.
• 8.8. Muscle tissue had the lowest CCO activity and was unaffected by temperature.
• 9.9. The high CCO activity at a cold acclimation of temperature 12°C was probably due to thermal compensation and the high activity at 36°C may have been a result of thermal stress.

     

Heart rate and blood pressure in bullfrogs during prolonged maintenance in water at low temperature

• 1.1. Bullfrogs were maintained in air-saturated water at 4°C under an 8:16hr, light:dark, photoperiod for 50 days from December to February.
• 2.2. Heart rates and mean arterial pressures from these submerged frogs remained stable throughout the entire period in the cold. The slow heart rates that were observed appeared to result from a combination of low temperature and submergence. No indication of torpor was observed in any of the animals.
• 3.3. These findings demonstrate that the cardiovascular system of bullfrogs apparently retains normal regulatory function when these animals are maintained under temperature and photoperiod conditions analogous to those found during overwintering.

     

Comparative studies of sodium transport and its relation to hydrostatic pressure in deep and shallow water gammarid crustaceans from Lake Baikal

• 1.1. Freshwater gammarids from 900–1400 m depths lose Na at 1 atm, 4°C, while related shallow water gammarids are near neutral Na balance.
• 2.2. Na⁺ influx rates are similar at 1 atm, 4°C, for abyssal and shallow water gammarids of similar weight.
• 3.3. Na⁺ efflux is faster for abyssal gammarids than for comparable shallow water gammarids.
• 4.4. Compressing abyssal gammarids to 90–140 atm increases Na⁺ influx rates enough to restore neutral Na balance, while in shallow water crustaceans, compression decreases Na⁺ influx.
• 5.5. Na⁺ influx rates in Baikalian gammarids vary with the 0.55 power of weight.
• 6.6. The equation F_{ma × t} = 1.3 × W^0.55 μEq/hr/animal applies to freshwater crustaceans over the weight range from 0.03 to 35 g.

     

Variations in response to environmental hypoxia of different colour forms of the shore crab,Carcinus maenas

• 1.1. The oxygen consumption of red and green Carcinus in normoxic and hypoxic sea water was determined, using an oxygen electrode in a sealed respirometer.
• 2.2. The red crabs had significantly higher “excited” oxygen uptake rates and a lower ability to compensate for hypoxia than the green crabs.
• 3.3. Red Carcinus display an emersion response to declining oxygen at lower oxygen tensions than the green crabs.
• 4.4. Mortality of red crabs exposed to prolonged anoxia was much greater.
• 5.5. The relationship of these findings to the zonation of the two colour forms on the shore is discussed.

     

Effect of temperature on oxygen consumption and heart rate of the australian crayfish Cherax tenuimanus (Smith)

• 1.1. Oxygen consumption at 18°C was 60% of the rate at 22 and 26°C.
• 2.2. Critical points, where the rate of oxygen consumption changed, were defined at 22°C (2.89 mg DO) and 26°C (3.46 mg DO). Linear regressions were fitted showing that oxygen consumption declined significantly (81.5% ±4.5) below the critical point.
• 3.3. Oxygen consumption was proportional to weight. Allometric relationships resulted in variable temperature-related coefficients for respiratory dependence on weight, a reflection of the crayfish adaptation towards re-establishment of a new equilibrium state.
• 4.4. Heart beat rate was lower at 18°C, and highest at the acclimation temperature (22°C). Stress at 26°C was evident.

     

Heart rate and its cholinergic control in the sole (Solea vulgaris), acclimatized to different temperatures

• 1.1. The effects of thermal acclimatization at 10 and 24°C on heart rate were investigated on unrestrained soles (Solea vulgaris).
• 2.2. The sensitivity of heart rate to temperature changes induced by temperature acclimatization was higher in cold-acclimatized than in warm-acclimatized soles.
• 3.3. Heart rate of cold-acclimatized fish to temperature changes was not affected by blocking the vagal tone with atropine.
• 4.4. After atropine treatment the ability of heart rate to show thermal compensation decreased in warm-acclimatized soles.
• 5.5. It is suggested that the vagus nerve can function differently at different temperatures.

     

The thyroid gland and temperature regulation in the prairie vole,Microtus ochrogaster and the chipmunk Tamias striatus

Absract

• 1.1. The basal metabolism of the vole, Microtus ochrogaster, a non-hibernator is about 80% below that expected for microtine rodents, while the basal metabolism of the chipmunk, Tamias striatus, is about 20% below that expected for small mammals.
• 2.2. Blocking thyroid secretion results in a 3°C improvement in the vole. and a 2°C improvement in the chipmunk, to the highest air temperature tolerated.
• 3.3. Blood levels of thyroxine in both species did not change as a function of ambient temperatures, whereas rates of radioiodine release were reciprocally related to ambient temperature.
• 4.4. There was no indication that the thyroid gland of the chipmunk was ever inactive either preceding, or during, hibernation.

     

The effects of temperature and moisture on survival capacity,cuticular permeability,hemolymph osmoregulation and metabolism in the scorpion,Centruroides hentzi (banks) (scorpiones,buthidae)

• 1.1. The temperature and water relations of Centruroides hentzi females were investigated. At 12 and 72% relative humidity (RH), the lower and upper Lt₅₀ were -4.5 and 43.7°C, and -4.7 and 45.1°C, respectively. When exposed to high temperature stress, survivorship was significantly greater under mesic conditions.
• 2.2. Cuticular water loss was higher under xeric conditions (12% RH), ranging from 0.061 mg/cm²/hr at 30°C to 0.211 at 41°C.
• 3.3. Exposure to dry air (0–5% RH) resulted in a significant increase in hemolymph osmolality: from 441 to 688 mOsm over a 5 day period.
• 4.4. Mean oxygen consumption rates increased from 161.7 mm³/g/hr at 34°C to 541.6 at 44°C. ATPase activity was significantly higher in animals acclimated and tested at 35°C.

     

Effects of membrane-perturbing drugs and noradrenalin on cAMP accumulation and red cell water content in carp (Cyprinus carpio) red cells

• 1.1. Carp red cells were treated with drugs that affect the cell membranes. The water content of the cells and the accumulation of cAMP in the cells were measured in normoxia and in hypoxia using non-stimulated and adrenergically stimulated cells.
• 2.2. WGA, DIDS + CCCP and A23187 increased the water content of nonstimulated normoxic cells.
• 3.3. In hypoxia ouabain and DIDS + CCCP increased the water content but cytochalasin B, NPM, DIDS, CCCP and A23187 + CA²⁺ abolished the hypoxia-induced swelling.
• 4.4. Any membrane perturbation induced some cAMP formation, Sophora and Anquilla lectins being most potent.
• 5.5. Also in adrenergically stimulated cells, membrane perturbation generally increased cAMP formation.
• 6.6. However, cAMP accumulation diminished in cells treated with cytochalasin B, CCCP and DIDS + CCCP.
• 7.7. The adrenergic swelling of carp red cells was reduced in normoxia by DIDS. NPM and CCCP increased the adrenergic swelling in normoxia to hypoxic level.
• 8.8. In hypoxia WGA and Anquilla lectin decreased the swelling.

     

Changes in high-energy phosphate metabolism in the water scorpion,Ranatra chinensis,under cold water-warm water stress

• 1.1. To evaluate changes in high-energy phosphate metabolism in the water scorpion (Ranatra chinensis) under restraint and cold water-warm water stresses, in vivo [³¹P]NMR spectra were obtained.
• 2.2. Under restraint stress, arginine phosphate (Arg-P) decreased by 10% after 1 hr and remained at that level thereafter, while β-ATP showed negligible changes over 6 hr.
• 3.3. As the water temperature gradually increased or decreased, the relative concentration of Arg-P decreased due to enzyme regulation.
• 4.4. Repeated cold water-warm water stress, which consisted of repeated 15 min exposures to cold water (5°C) followed by 15 min exposures to warm water (30°C) caused distinct decreases in Arg-P and β-ATP concentration. These decreases were dependent on the frequency of exposure.
• 5.5. Phosphomonoesters (PME) increased not only with restraint stress but also with cold water-warm water stress.
• 6.6. The effect of cold water-warm water stress on high-energy phosphate metabolism was greater than that of restraint stress.

     

Metabolic rate and body temperature of adult and juvenile hyrax (Procavia capensis)

• 1.1. Resting metabolic rates (RMR) below thermoneutrality in adult hyrax acclimated to 26, 15 and 10°C remained unchanged, i.e. thermal conductance (K) remained constant.
• 2.2. Conductance in juveniles decreased with acclimation to lower ambient temperatures (T_a).
• 3.3. Body temperature (T_b) dropped by 3.8°C in adults exposed to T_a of 30 – 5°C. The decrease was constant.
• 4.4. Body temperature fell by 1.5°C in juveniles exposed to T_a of 30 – 20°C but stabilized between 20 and 5°C.
• 5.5. The labile T_b, associated with behavioural strategies and lower than predicted RMR, can be seen as an energy-conserving mechanism of particular importance during winter conditions.

     

Sea-water tolerance in freshwater-resident arctic charr (Salvelinus alpinus)

• 1.1. Freshwater-resident Arctic charr acclimated for 2 months at 8°C, 15% were divided into four experimental groups in July and exposed to 1 and 8°C in 15 and 34% salinity.
• 2.2. Only slight changes in gill Na-K-ATPase activity, blood plasma osmolality and blood plasma concentrations of Cl⁻ and Mg²⁺ were found for the fish exposed to 1 or 8°C in brackish water.
• 3.3. When exposed to sea-water at 8°C, an increase in osmolality and in concentrations of Cl⁻ and Mg²⁺ took place during the first 2–3 days, after which it levelled off.
• 4.4. If exposed to sea-water at 1°C, however, marked increases were found for all parameters measured and all the fish were dead within 5 days of exposure.
• 5.5. These results show that freshwater-resident Arctic charr—if acclimated to brackish water—can survive in sea-water during summer if the environmental temperature is not too low.

     

Oxygen binding of intact coelomic cells and extracted hemoglobin of the echiuran Urechis caupo

• 1.1. The oxygen affinity of Urechis caupo coelomic cells is the same in normoxic and in hypoxic animals. There is no Bohr effect between pH 6.8 and 8.0.
• 2.2. The oxygen affinity of intact coelomic cells is the same as that of extracted, stripped hemoglobin. The oxygen binding properties of stripped hemoglobin are not affected by 1 mM ATP, IMP, or hydrogen ions between pH 6.8 and 8.0, nor do they clearly show cooperativity. The heat of oxygenation. ΔH, = −13.1 kcal/mol between 10 and 25 C.
• 3.3. Although U. caupo coelomic cell hemoglobin is tetrameric and intracellular, it apparently exhibits neither heterotropic nor homotropic interactions.

     

Effects of temperature and acid stress on hatching,survival capacity,metabolism and postural reflexes in caenid mayflies (ephemeroptera)

• 1.1. Mortality was 100% at pH 3.5 over a temperature range of 10–30°C for embryos and nymphs of Caenis diminuta and C. hilaris.
• 2.2. Hatching success for both species was highest at pH values above 4.5.
• 3.3. Survival capacities were significantly higher at 20°C over a pH range of 4.0-7.2.
• 4.4. Oxygen consumption rates increase as a function of increasing temperature and reduced acidity.
• 5.5. Loss of the nymphal righting response was observed at pH 3.5. This response can be used as a behavioral assay for acid stress.

     

Genome size and metabolic rate in salamanders

• 1.1. The relationship between genome size (C-value) and metabolic rate in salamanders was examined by correlation analyses.
• 2.2. The C-values of 48 species of salamanders were determined by flow cytometry measurement of DNA quantity in erythrocyte nuclei; C-values of 88 species were taken from the literature.
• 3.3. Standard metabolic rates for salamanders at 5, 15, 20 and 25°C were taken from the literature.
• 4.4. Only at 25°C is there a robust, significant correlation between C-value and metabolic rate, and the hypothesis of a frugal metabolic strategy and genome size effect on metabolic rates in salamanders is discussed.

     

Behavioural thermoregulation and critical thermal limits of Macrobrachium acanthurus (Wiegman)

• (1)The preferred temperatures of Macrobrachium acanthurus were determined for prawns acclimated to 20°C, 23°C, 26°C, 29°C and 32°C, and the final preferendum estimate was (29.5°C).
• (2)The critical thermal minima (CTMin) and maxima (CTMax) were 11.0°C, 12.1°C, 13.0°C and 14.8°C, and 34.2°C, 35.0°C, 36.1°C and 39.8°C, respectively.
• (3)The zone of thermal tolerance assessed using the CTMin and CTMax boundaries was 644°C².
• (4)The acclimation response ratio was between 0.33 and 0.62.
• (5)To cultivate this species in the southeastern region of México it should be done in not <15°C (CTMin) during the winter and below 38°C in summer (CTMax).