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1. 1. The rates of rehydration from a varying soil particle size was investigated for two species of toads, Bufo boreas and Bufo punctatus. 2. 2. Both species of toads were found to gain comparatively equal rates of water per unit of surface area, about 40 mg/cm2 per hr. However, the larger surface area to volume ratio of B. punctatus allows this anuran to regain its deficit at a significantly faster rate than B. boreas. B. punctatus showed rates of about 3 per cent standard weight gain per hr while B. boreas showed rates of about 1.5 per cent standard weight gain per hr. 3. 3. It is proposed that a reduced size (i.e. increased surface area to volume ratio) may be an important adaptation to xeric environments. Published...
1. 1. The tolerance of the muscles of two desert toads, Scaphiopus couchi and Bufo cognatus, and Rana pipiens, an aquatic frog, was measured in hypertonic sucrose, urea and NaCl. 2. 2. It was shown that the muscles of B. cognatus and S. couchi can tolerate higher osmotic concentrations of sucrose than R. pipiens, and in addition the isometric tension produced by the muscles of the toads is higher at all sucrose concentrations than the isometric tension produced by the aquatic frog, R. pipiens. 3. 3. It is concluded that the combined phenomena of water loss and increased concentrations of inorganic ions critically limit the efficiency of anuran muscles in contracting. 4. 4. The effect of increased concentrations...
Cardiac chamber enlargement and hypertrophy are normal physiologic responses to repetitive endurance exercise activity in human beings and domestic dogs. Whether similar changes occur in wild animals as a consequence of increased activity is unknown. We found that free-ranging gray wolves (Canis lupus, n=11), the archetypical endurance athlete, have electrocardiographic evidence of cardiac chamber enlargement and hypertrophy relative to sedentary captive gray wolves (n=20), as demonstrated by significant increases in QRS duration, QT interval, and QT interval corrected for heart rate, a tendency towards increased Q, R, and S wave voltages in all leads, and a significant decrease in heart rate. We conclude that exercise...
1. Heating and cooling rates of the desert tortoise, Gopherus agassizii, were measured in the field and in the laboratory. 2. Heating rates in the field were up to ten times faster than cooling rates. 3. Under controlled conditions, heating rates equalled rates of cooling. 4. Heart rates during heating were significantly faster than during cooling at any particular body temperature. 5. Subcutaneous neck temperatures did not differ from cloacal temperatures during heating or cooling, suggesting a state of continuous vasodilation. 6. Results are interpreted as suggesting that behavioral postures and activities play a greater role than physiology in the determination of thermal exchange rates of the desert tortoise....
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1. Zinc uptake and distribution in the developing coho salmon egg was measured using radioisotope tracer techniques.2. The uptake was affected by pH, temperature, Cu2+, 2,4-fluorodinitrobenzene and the azo dye, malachite green; but not by azide ion or 2,4-dinitrophenol.3. About 70 per cent of the total accumulated zinc was bound, rather firmly, to the chorion; about 26 per cent was found in the perivitelline fluid, about 2 per cent in the yolk, and about 1 per cent in the embryo.4. Temperature, pH, inhibitor and kinetic studies indicated that zinc uptake involves physicochemical sorption to the chorion together with passive diffusion into the yolk and embryo.
1. 1. Deep body and shell surface temperatures were monitored via radio-telemetry from unrestrained desert tortoises in their natural habitat. 2. 2. The surface of the carapace acts as a buffer against solar radiation, resulting in deep body temperatures up to 10�C below shell surface at the time of the midday retreat to burrows. 3. 3. The burrow of the desert tortoise provides the only ambient temperatures at ground level which are below the lethal range for this species during midday hours. 4. 4. Evening retreat to burrows permits an extension of higher body temperatures into the mid-evening hours. 5. 5. The use of evening burrow retreats lessens in mid-summer. This behavioral change results in lower body temperatures...
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1. Rainbow trout were anesthetized with MS-222 (Sandoz) or methylpentynol and catheterized. Urine was collected at selected intervals up to 48 hr. 2. Effects of MS-222 anesthesia on urine flow and composition were isolated from the stress of catheterization by re-anesthetizing the fish 18 to 20 hr post catheterization. 3. Urine output patterns were similar following MS-222 or methylpentynol anesthesia and catheterization. Highest urine flows were measured 4 to 8 hr post treatment. The highest urine output after re-anesthetization with MS-222 was observed 2 to 4 hr post-anesthesia. 4. Highest concentrations of Na2+, K+, Ca2+, Cl- and inorganic PO4 in the urine were measured in the first 2 hr after anesthesia and...
1. 1. The apparent efficiency of assimilation of preformed water from both plant and animal diets by the lizard Dipsosaurus dorsalis increased about 10% between 34 and 40 C. 2. 2. This increase parallels the increase in apparent digestibility coefficient of food and probably results from an osmotic balance between chyme and the intracellular fluid of the gut. 3. 3. Desert iguanas are largely subterranean in summer, spending almost 90% of the day in burrows. Under the conditions they encounter there, the increased assimilation of preformed water with increasing body temperature equals the increase in evaporative water loss. Published in Comparative Biochemistry and Physiology, volume 72, issue 1, on pages 221 - 224,...
1. Renal structure and urine concentrating capacity varied significantly among nine populations of desert ground squirrels representing four closely related taxa. 2. Variation in renal structure was weakly associated with taxonomic grouping. 3. Urine concentrating capacity was not correlated with standard measures of habitat aridity, but it was correlated with soil salinity. 4. Maximum urine osmolalities for one population from the most saline habitat were among the highest documented for sciurid rodents. 5. Results do not support the hypothesis that hibernating sciurids have poor renal efficiency. Published in Comparative Biochemistry and Physiology, volume 92, issue 4, on pages 3 - 3, in 1989.
Brown trout, Salmo trutta, exposed to heavy metals (mainly Cd and Zn) for at least 2 years in the Eagle River, Colorado, were examined for liver size and activity of the growth-promoting enzyme, ornithine decarboxylase (ODC) and compared to trout living in an uncontaminated site. Liver-somatic index (LSI) was greater for trout living in the uncontaminated site with the LSI of females being significantly greater than that of males. The LSI for females at the uncontaminated site was greater than that of females at the contaminated site, but males were not different statistically. ODC activity in the livers of both males and females was lower at the contaminated site. However, males and females did not differ with...
1. 1. The effect of short-term (79 hr) food deprivation at 27°C on body mass, locomotor activity, body temperature (Tb), and resting oxygen consumption was determined in eleven American kestrels (Falco sparverius). 2. 2. The change in body mass during resting followed the relation, % mass remaining = 99 e0.07(days fasting). There was no significant difference in the rate of relative mass loss between males and females. 3. 3. Locomotor activity, measured as perch hopping, was highly variable in both control and fasted birds and showed no correlation with stage of the fast, basal metabolic rate (BMR), or rate of mass loss during food deprivation. 4. 4. Body temperatures of fasted birds declined continuously by 0.2–0.4°C...
1. 1. Metabolic rates are presented for (1) two females and one male kestrel incubating eggs in the field. (2) the same individuals in the laboratory immediately following the incubation period, (3) non-breeding kestrels and (4) kestrel eggs for 10 days during their development. 2. 2. The results from one male and one female support the idea that incubation can be accomplished at the level of adult resting metabolism. 3. 3. Metabolism of the other female during incubation was greater than adult resting metabolism at air temperature below 15�C. Egg metabolism rises exponentially during mid-incubation period and reaches a plateau in the last 5?6 days at 21.2 mg CO2/egg per hr. 4. 4. In the last 5 days of the incubation...
1. 1. Field samples of urine, blood plasma, and kidneys were collected seasonally from white-tailed prairie dogs (Cynomys leucurus) and black-tailed prairie dogs (C. ludovicianus). 2. 2. Maximum field urine osmolalities for black-tailed prairie dogs were significantly below maximum urine osmolalities for that species under laboratory water deprivation. However, white-tailed prairie dogs produced field urine concentrations that did not differ from maximum urine osmolality collected under laboratory water deprivation except during June. 3. 3. Black-tailed prairie dogs demonstrated greater urine concentrating ability than white-tailed prairie dogs as evidenced by kidney relative medullary thickness and by urine concentration...
1. 1. The average daily heart rate (HR) of eight kestrels was used with O2 consumption (Image )-HR relationships measured on each individual to estimate their daily energy metabolism. Hea rate provided a good index of daily metabolism (i.e. less than 10% error) in some individuals. The unpredictable shifts that occur in the resting VO2-HR relationship over periods of days, weeks or months is a major shortcoming of the heart rate method. 2. 2. Heart rate, when sampled for l min every 10 min throughout a 24-hr period provides a very good measure of the true average daily HR of some kestrels. 3. 3. Suggestions for potential users of the heart rate method are given Published in Comparative Biochemistry and Physiology,...
1. 1. Various blood constituents were measured in an attempt to identify the effects of exposure of Great Plains toads to the critical thermal maximum (CTmax) and determine the time course of the onset of and recovery from these effects. 2. 2. Tests for generalized tissue damage inclucling serum glutamic-oxalacetic and glutamic-pyruvic transaminases (SGOT, SGPT), total protein and blood urea nitrogen (BUN) were unaffected by acute thermal stress. 3. 3. Hematocrit, erythrocyte number, mean cell volume and hemoglobin concentration were also unchanged. 4. 4. Blood glucose, lactic acid and creatine phosphokinase (CPK) levels all increased significantly. 5. 5. Blood pH, PO2 and HCO3? also increased with acute heat stress...
1. 1. Changes in rates of water exchange similar to those caused by dehydration (enhanced cutaneous uptake and reduced urinary loss) are elicited by injection of hyperosmotic solutions of NaCl or sucrose. 2. 2. Rates of water exchange bear the same relation to plasma sodium concentration in both dehydrated and NaCl loaded toads. 3. 3. Injection of a hyperosmotic urea solution does not affect rates of water exchange. 4. 4. Loss of blood causes toads to take up amounts of water greater than those excreted. 5. 5. Small volumes of plasma from dehydrated toads cause cutaneous water uptake to exceed urine production when injected into hydrated individuals. Published in Comparative biochemistry and physiology, volume 15,...
1. 1. Annual testis cycles in the lizards Dipsosaurus dorsalis and Xantusia vigilis are regulated by both exogenous, especially thermal, stimuli and an endogenous rhythmicity. 2. 2. High temperatures appear to be the primary cue for stimulating spermatogenesis and androgenesis in spring. 3. 3. Photoperiod affects X. vigilis in mid-winter (long days stimulate the testes), but only at high body temperatures, and photoperiodic sensitivity is lost by March. 4. 4. Testis regression appears to be essentially independent of photoperiod and temperature in both lizards, and an endogenous rhythm is postulated. 5. 5. A prolonged, post-nuptial, sexual refractory period accounts for the suppression of spermatogenic activity...
1. 1. Desert iguanas, Dipsosaurus dorsalis, collected at different times of the year in the Coachella Valley, California, showed no signs of dehydration or accumulation of electrocytes. 2. 2. Variations in body water content and in the distribution of body fluids were related to variations in the amount of fat in the animal. 3. 3. Electrolyte concentrations did not vary in the plasma or intracellular fluid. Variations in urinary electrolytes were correlated with variations in dietary electrolytes. 4. 4. Significant quantities of cations were excreted in the urine as precipitated urate salts. The low solubility of these salts permits their excretion with a small loss of water. Published in Comparative Biochemistry...