Showing papers in "Physiological and Biochemical Zoology in 1985"
TL;DR: FieldTb data indicate that all functions would be near maximum levels during the day but would be significantly reduced at night, and concludes that no single Tb is best for the ecological tasks of prey capture, predator avoidance, and energy conservation.
Abstract: The body temperature ( $T_{b}$ ) of garter snakes (Thamnophis elegans) can vary considerably in the course of a day (e.g., 4-33 C), and information on how $T_{b}$ affects physiological and behavioral processes is required to evaluate the significance of that variation. We measured crawling speed, swimming speed, tongue-flicking rate, digestive rate, and oxygen consumption at $T_{b}'s$ of 5-35 C in snakes collected in eastern Washington and acclimated to September field photoperiod and temperature cycles. All functions were strongly dependent on $T_{b}$ . The maximum speed of crawling ( $\bar{X} = 0.74 m s^{-1}$ ) occurred at $T_{b} = 34.5 C$ ; that of swimming ( $\bar{X} = 0.69 m s^{-1}$ ) occurred at $T_{b} = 28.5$ . At $T_{b} , the snakes crawled more slowly than they swam, but the reverse was true at higher $...
302 citations
TL;DR: Differences in water content cannot explain the greater desiccation resistance of flies from postponed-senescence populations, but genetically increased life span in these D. melanogaster populations appears to result proximally from greater resistance to mortality arising from environmental stress.
Abstract: Adult Drosophila melanogaster from populations that exhibit postponed senescence were compared to flies from control populations. Male and female flies from populations displaying postponed senescence were significantly more resistant than control flies to desiccation, starvation, and the vapor of a 15% ethanol solution. In the presence of desiccant or when humidity was not controlled, flies from postponed-senescence populations were more resistant than controls to heat stress in the range 37-39 C. Differences in heat tolerance disappeared when experiments were conducted at high humidity. Tolerance to starvation increased with age for females but remained approximately constant for males. Tolerance to desiccation decreased with age for both sexes. Differences between control and postponed-senescence populations with respect to starvation resistance and desiccation resistance were obtained at all ages examined. Females from postponed-senescence populations had lower proportional water content than did fema...
294 citations
TL;DR: Estimating the metabolic rates of juvenile squamates from equations based on comparisons among species is invalid because there is significant variability among mass exponents among the 14 species that met the statistical requirements for analysis of covariance, and a common mass exponent cannot be assumed for intraspecific comparisons.
Abstract: We used multiple regression analysis to evaluate the relationship between metabolic rate and three independent variables-mass, temperature, and standard or resting state-for squamate reptiles. For comparisons among adults of different species, mass raised to the .80 power explains 88% of the variation in metabolic rate. (The .80 mass exponent is significantly greater than the .75 predicted by theoretical considerations.) A further 8% of the variation in metabolic rate is explained by body temperature and whether the lizard is in a standard or resting metabolic state. Residuals were used to determine whether metabolic rates varied as a function of phylogenetic relationship or ecological grouping. Familial associations explained 16% of the variation in metabolic rate for varanids, lacertids, iguanids, colubrids, scincids, xantusiids, gekkonids, and boids. More variation (45%) was explained when lizards were partitioned into four ecological categories: day-active predators, hervibores, reclusive predators, a...
290 citations
TL;DR: Pulmonary and non-pulmonary O2 uptake of freshwater turtles (Chrysemys picta bellii) at 3, 10, 15, and 20 C were measured on freshwater turtles as discussed by the authors, and these data were related to the physiological responses of turtles to submergence in aerated vs. anoxic water.
Abstract: Pulmonary and nonpulmonary O2 uptake (\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}${\mathrm{\dot{V}_{O_{2}}}}$\end{document}) were measured on freshwater turtles (Chrysemys picta bellii) at 3, 10, 15, and 20 C, and these data were related to the physiological responses of turtles to submergence in aerated vs. anoxic water. Total \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}${\mathrm{\dot{V}_{O_{2}}}}$\end{document} increased with temperature...
225 citations
TL;DR: From calculations, body drag during gliding phases may more than double during active swimming by seals and influences the swimming performance of these animals.
Abstract: Hydrodynamic characteristics, including fineness ratios, coefficients of drag, and the influence of body size, shape, and position on drag were examined for harbor seals (Phoca vitulina). Drag for towing animals increased curvilinearly with velocity over the range 0.7 to 3.5 m·s⁻¹ and was described by the equations: Drag(N) = 6.49 velocity ($m\cdot{s}^{-1})^{0.79}$ for a submerged adult seal, and Drag(N) = 1.29 $e^{1.9 velocity (m\cdot{s}^{-1})}$ for the seal towing at the water surface. The importance of streamlining was demonstrated by comparing these values with those of a towing human subject. At 2.0 m·s⁻¹ drag for a submerged human was 113 N, representing a 5.0-fold and a 1.9-fold increase in drag over submerged and surface towing seals, respectively. Coefficients of drag (Cd) followed this trend and were three times greater for the human subject. Alterations in body configuration of the seals, as occurs during stroking movements, resulted in an increase in body drag. From our calculations, body drag...
182 citations
TL;DR: The swimming metabolism of yearling and adult harbor seals was measured by indirect calorimetry in a flow channel at speeds ranging from 0.5 to 1.4 m·s−1 and the minimum cost of transport was less than for other semiaquatic birds and mammals but 3–4 × the predicted value for salmonid fish of equivalent size at 25 C.
Abstract: The swimming metabolism of yearling and adult harbor seals was measured by indirect calorimetry in a flow channel at speeds ranging from 0.5 to 1.4 m·s⁻¹. Minimum resting metabolic rates in still water were 5.1 and 4.6 ml O₂·min⁻¹·kg⁻¹ for the two yearling seals (body mass [$M_{b}$] = 33 kg) and one adult seal ($M_{b} = 63 kg$), respectively. Minimum resting metabolic rates were about 1.1 X the predicted standard metabolic rate for mammals of equivalent size. During steady-state swimming, metabolism increased curvilinearly with speed and was best described by the equation $\dot{V}O_{2} (ml O_{2}\cdot{min}^{-1}\cdot{kg}^{-1}) = 5.1 + 6.25$ velocity $(m\cdot{s}^{-1})^{1.42}$ for the yearling seals and $\dot{V}O_{2} = 4.6 + 3.1$ $velocity^{1.42}$ for the adult seal. Stroke frequency increased linearly as a function of swimming speed. Cost of transport decreased asymptotically with swim velocity, approaching a minimum at 1.0-1.4 m·s⁻¹ of 3.6 J·m⁻¹·kg⁻¹ for yearling and 2.3 J·m⁻¹·kg⁻¹ for adult seals. The mini...
144 citations
TL;DR: It is concluded that the prolonged tolerance to anoxia at 3 C is not due to specialized mechanisms absent at higher temperatures; rather, slow accumulation of plasma lactate, modest hypercapnia, and effective compensatory ion changes markedly retard the development of acidosis at this temperature.
Abstract: Blood acid-base status and plasma ion concentrations and osmolality of freshwater turtles (Chrysemys picta bellii) were measured periodically during and following submergence in N₂-equilibrated water (Po₂ < 5 torr) at 3, 10, 15, and 20 C. Submergence durations that resulted in similar reductions in blood pH or in plasma [HCO₃⁻] at each temperature were 12 h at 20 C, 3 days at 15 C, 10 days at 10 C, and 13 wk at 3 C. At 3 C, 75% of the fall in pH during anoxia was due to metabolic acidosis, but the contribution of respiratory acidosis to the pH drop increased with temperature, being 50% at 10 C, 73% at 15 C, and 73% at 20 C. Plasma strong-ion difference decreased much less during anoxia than had been predicted on the basis of the increase in plasma lactate, owing to compensatory changes in plasma ions, including increased [K⁺], total [Ca⁺⁺], and total [Mg⁺⁺] and decreased [Cl⁻]. The magnitude of these ion changes was directly correlated with the increase in plasma lactate, which in turn was inversely corre...
127 citations
TL;DR: The capacity of male spring peeper trunk muscles for aerobic metabolism exceeds considerably the highest values yet reported for ectothermic vertebrate muscle tissue and is comparable to highly oxidative muscles of endotherms.
Abstract: Oxygen consumption by male spring peepers (Hyla crucifer) increased linearly with calling rate, reaching peak values of 1.5-1.7 ml O₂/(g · h) at the highest calling rates. The intercept of the regression line describing the relationship between metabolism and calling rate does not differ significantly from daytime resting metabolism (0.11 ml O₂/[g · h]). Metabolic rate during vigorous locomotor exercise at the same temperature (19 C) was only 1.1 ml O₂/(g·h). We measured activities of mitochondrial enzymes in the trunk muscles (internal and external obliques) involved in sound production and in mixed hind limb muscles of male and female frogs. Male trunk muscles were very large, accounting for 15% of total body mass, whereas female trunk muscle constituted only 3% of total body mass. Citrate synthase (CS) activity in male trunk muscle, indicative of oxidative capacity, was six times the CS activity in leg muscle (86 vs. 14 μmol/[min · g fresh muscle at 20 C]) and 17 times the CS activity in female trunk m...
96 citations
TL;DR: Although general metabolic responses to temperature change may be extrapolated to the natural environment, environmental factors other than temperature-such as photoperiod and diet-may contribute to modification of these responses in certain tissues of naturally acclimatized fishes.
Abstract: Maximal enzyme activities in tissues from 5 C- and 25 C-acclimated chain pickerel (Esox niger) were compared with those from winter- and summer-acclimatized fish to determine whether laboratory studies of thermal acclimation can be extrapolated to the natural environment. Activities of enzymes from pathways of aerobic metabolism measured at 15 C were higher in most tissues of cold-acclimated and winter-acclimatized pickerel than those in tissues of warm-acclimated and summeracclimatized fish, respectively, indicating that general patterns of metabolic response are similar in acclimated and acclimatized groups. Activities of enzymes in all tissues of summe- and winter-acclimatized fish were lower than activities in 25 C- and 5 C-acclimated fish. Activity of carnitine palmitoyltransferase (CPT), an indicator of the capacity for fatty-acid utilization, was higher in brain and red muscle tissue of cold-acclimated compared with warm-acclimated fish but was lower in winter-acclimatized compared with summer-accl...
90 citations
TL;DR: Oxygen consumption (e.g., aastex} \usepackage{amsbsy} \usingpackage{amssymb] \use package{amsfonts},amssymm,amssyrm,amsxtra},wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} as discussed by the authors
Abstract: Oxygen consumption (\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}${\mathrm{\dot{V}_{O_{2}}}}$\end{document}), evaporative water loss (\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}$\dot{m}_{{\mathrm{we}}}$\end{document}), and body temperature (\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{por
73 citations
TL;DR: In this paper, the authors measured transcutaneous evaporation, skin and body temperature, and oxygen consumption in pigeons over a wide range of air temperatures and used a general Fick diffusion model to estimate integumental plus boundary layer resistance to diffusion of water vapor.
Abstract: To determine the cutaneous water-loss responses of birds to environmental temperature, we measured transcutaneous evaporation, skin and body temperature, and oxygen consumption in pigeons over a wide range of air temperatures. We used a general Fick diffusion model to estimate integumental plus boundary layer resistance to diffusion of water vapor. Cutaneous water loss (mean ± SE) increased from 1.4 ± 0.09 mg m⁻² s⁻¹ at 0 C to 3.0 ± 0.09 mg m⁻² s⁻¹ at 30 C and increased sharply to 9.0 ± 0.32 mg m⁻² s⁻¹ at 40 C. Whole-body vapor diffusion resistance of pigeons (mean ± SE) varied with air temperature, decreasing from 130.0 ± 8.2 s/cm at 0 C to 97.0 ± 4.1 s/cm at 30 C and to 45.0 ± 3.4 s/cm at 40 C. Measurements of the vapor resistance of the plumage made in isothermal diffusion chambers and estimates of the boundary-layer resistance to evaporation obtained from predictive equations indicate that the feather coat and associated layer of still air are together only 6.2%-25.8% of total vapor resistance and tha...
TL;DR: An energy analysis reveals that food intake fails to meet even resting metabolic requirements at temperatures below 10 C and that the net cost of spontaneous swimming activity is a small portion of the total daily energy expenditure from 3 to 17 C.
Abstract: Resting metabolic rate (MR), spontaneous swimming activity, and food intake were measured in order to learn the relationship between these responses and low acclimation temperatures. The fish were collected in the fall and placed in one of eight acclimation tanks ranging from 3 to 17 C at 2 C intervals for 3 wk. Food intake was measured during and after the acclimation period, and MR and activity were measured following the acclimation period. MR, measured in a closed system, was exponentially related to temperature with a $Q_{10}$ of 3.0. Food intake declined linearly down to 10 C, below which it became negligible. Spontaneous swimming activity, measured in an annular tank, was similar for all fish at or above 7 C and was considerably reduced at 5 and 3 C. These data indicate that physiological systems respond very differently to low acclimation temperatures in the largemouth bass. MR shows no compensation. The central nervous system, which mediates activity cycles, shows perfect compensation from 17 to ...
TL;DR: Minimum cost of pedestrian transport (Mrun) was determined by treadmill running and flow-through oxygen respirometry in three species of flightless beetles, Psammodes striatus, Pachysoma hippocrates, and Anthia fabricii by extrapolations of vertebrate-based regressions of Mrun on mass.
Abstract: Minimum cost of pedestrian transport ($M_{run}$) was determined by treadmill running and flow-through oxygen respirometry in three species of flightless beetles, Psammodes striatus, Pachysoma hippocrates, and Anthia fabricii. $M_{run}$ was 1.67, 4.76, and 2.15 ml O₂/(g • km) (where g • km = ml O₂/[kg • m]), respectively, in these three species, which have typical masses of 2.9, 3.1, and 2.2 g, respectively. Extrapolations of vertebrate-based regressions of $M_{run}$ on mass predict similar values of $M_{run}$ given these masses. When combined with those for mammals and birds <1,000 g, all published $M_{run}$ data on insects are related to mass by the equation $M_{run} = 0.530M^{-0.325}$, where M is in kg and $M_{run}$ is in ml O₂/(g • km). All species ventilated discontinuously while at rest.
TL;DR: The stable V̇o2 and reduced rates of growth and development during the delayed-hatching period extend the period of subsistence on energy reserves and probably represent adaptations to the variable and brief occurrence of standing water.
Abstract: Frogs in the genus Pseudophryne lay eggs on land in areas that are subsequently flooded. Embryos develop to Gosner stages 26-28 and then delay hatching until flooding occurs. We investigated the idea that embryos suspend development and conserve energy during this period. Oxygen consumption ($\dot{V}O_{2}$), dry body mass (excluding the digestive tract and yolk), and developmental stage were determined throughout development in embryos and hatchlings of P. bibroni that were raised in either aquatic or terrestrial conditions at 12 C for up to 140 days. During the 33 days following fertilization, the above parameters increased continually and were nearly identical in aquatic and terrestrial embryos. Aquatic embryos hatched at a mean age of 39 days when $\dot{V}O_{2}$ was 1.5 μl/h. Subsequently, resting $\dot{V}O_{2}$ of the unfed aquatic hatchlings increased rapidly to a peak of 2.2 μl/h at 47 days and then declined. $\dot{V}O_{2}$ of terrestrial embryos, however, peaked at 1.1 μl/h at 33 days and then stab...
TL;DR: It appears, then, that changes in ESA in the posterior gills are important only in hyperosmotic regulation and in active Na uptake in dilute media.
Abstract: Male sand fiddler crabs, Uca pugilator, permitted to enter or leave seawater (SW) media at will (natural environment) hyperosmoregulated in 10% and 50% SW and hypoosmoregulated in 150% and 200% SW. Crabs forced to remain submerged in the SW media (immersion) did not osmoregulate as well, particularly in 150% and 200% SW. Gill sodium-plus-potassium-activated ATPase (Na,K-ATPase) specific activity was characterized in crude homogenates, and optima for K, Mg, ATP, and pH were determined. After 21 days acclimation in a 10% SW natural environment, gills 1, 2, 5, and 6 showed significant increases in gill enzyme-specific activity (ESA) compared to 100% SW controls. Acclimation to 50% SW caused significant increases in ESA only in gills 5 and 6; acclimation to 150% and 200% SW natural environments decreased or did not significantly change ESA. Gills 5 and 6 contained approximately 75% of total gill ESA in all media. Crabs immersed in the SW media showed similar changes in gill ESA. It appears, then, that changes...
TL;DR: Male European starlings, Sturnus vulgaris, were implanted with varying dosages of testosterone in June, shortly before the natural onset of the molt, and dose-dependent effects on the primary, secondary, and body molts were found.
Abstract: Male European starlings, Sturnus vulgaris, were implanted with varying dosages of testosterone in June, shortly before the natural onset of the molt. Dose-dependent effects on the primary, secondary, and body molts were found. In general, testosterone delayed the onset of molt and slowed its progress. Since the duration of the molt was relatively unaffected, the molt in testosterone-treated birds stopped before its completion. It was not resumed when the implants were removed in November. The plasma testosterone levels in all implanted birds tended to be lower during the molt than afterward. The opposite was true of thyroxine plasma titers. A negative correlation was found between testosterone levels during the molt and the final molt score, and a positive correlation was found between thyroxine and the final molt score.
TL;DR: Conditions for respiration within the spherical egg masses of the pickerel frog, Rana palustris, are reassessed to demonstrate that the center of ranid egg masses is not severely hypoxic and not limiting to aerobic metabolism.
Abstract: Earlier studies of gelatinous egg masses laid by many amphibians suggested that the egg mass center was extremely hypoxic and that embryos located there suffered delayed growth and high mortality. The present study has reassessed conditions for respiration within the spherical egg masses of the pickerel frog, Rana palustris. Partial pressures of O₂ and CO₂, and the pH of egg jelly, as well as lactate concentration of embryonic tissue, were measured at 1-cm depth increments from surface to center of the egg mass. Oxygen uptake of intact egg masses and eggs separated from the mass was determined as a function of temperature and ambient O₂ levels. Although significant gradients for O₂, CO₂, and pH existed from surface to center, the magnitude of these gradients was too small to directly affect O₂ uptake of the egg mass or individual eggs under a variety of experimental conditions likely to occur in nature. Exchange of gases between the egg mass surface and center occurs primarily by diffusion through the egg...
TL;DR: It is suggested that behavioral abnormalities brought on by acid stress are responsible, in part, for the disappearance of fish populations from lakes and streams where pH's have been chronically depressed by acid pollution.
Abstract: The effects of acid stress on the locomotor and chemoreceptive behavior of Arctic char were determined by quantifying their movements within a laboratory trough. Three behavioral parameters were measured: activity, spatial preference within the trough, and the attraction to a plume of food extract presented at different concentrations. Char were preexposed for 14 days to pH 7.8 (controls), 7.0, 5.5, 5.0, 4.75, or 4.5, and then individually tested in the trough at the same pH. The behavior of pH 7.0 and 5.5 char was not statistically different from the controls. Char exposed to pH 5.0 behaved much like control fish but were more active and less responsive to the extract. Marked behavioral changes occurred when char were exposed to either pH 4.75 or 4.5. At these levels activity was sharply reduced, time spent at the ends of the trough increased, and attraction for the extract was highly depressed. Some individuals were strongly affected, while others were affected only moderately. We suggest that behaviora...
TL;DR: Although water fluxes increased with age, younger nestlings retained a greater proportion of incoming water than did older birds, and growth efficiency, i.e., the ratio of energy accumulated in tissues divided by the total metabolizable energy (TME), was higher than most of those reported for other altricial nestlings.
Abstract: We measured water fluxes and CO₂ production rates of nestling Belding's savannah sparrows (Passerculus sandwichensis) in the field, using doubly labeled water. We found no significant difference between rates of water flux or CO₂ production of nestlings in broods of two compared with broods of three young, so we pooled these results. Nestlings were growing rapidly, and water influx nearly always exceeded water efflux. Although water fluxes increased with age, younger nestlings retained a greater proportion of incoming water than did older birds. Nestling sparrows gained a total 51.1 ml H₂O during the 8-day nestling period, and they lost 43.4 ml. Nestlings apparently did not consume free water of any kind. Metabolic rates (ml CO₂/h) increased with age (days after hatching) according to the relationship, ml $CO_{2}/h = 1 16.7/[1 + 17.9e^{(-046)} age]$. Nestling savannah sparrows accumulated 75.2 kJ of energy in growth, and respired energy amounted to 171.5 kJ. For the 8-day nestling period, growth efficienc...
TL;DR: It is proposed that these substances are then transported in the circulatory system of the animals to the bacteria in the trophosome, where malate is decarboxylated and the CO2 released is incorporated in the bacteria.
Abstract: Specimens of the large pogonophoran tube worm Riftia pachyptila were collected at the hydrothermal vents at 21°N on the East Pacific Rise (20°50′ N, 109°06′ W). Incubations of live animals in the presence of radiolabeled CO2 showed an incorporation of radioactivity in the obturacular plume into malate and succinate. It is proposed that these substances are then transported in the circulatory system of the animals to the bacteria in the trophosome, where malate is decarboxylated and the CO2 released is incorporated in the bacteria. A CO2 fixation rate of up to 16 μmol/h−1/g fresh wt−1 could be observed in the obturacular plume. Several carboxylating enzymes were tested; pyruvate carboxylase and malic enzyme (NADP) had an activity of 0.04 U/g fresh wt−1, and phosphoenolpyruvate carboxykinase (GDP) 0.01 U/g fresh wt−1; acetyl CoA carboxylase, malic enzyme (NAD), phosphoenolpyruvate carboxykinase (ADP), and phosphoenolpyruvate carboxylase could not be detected. The quantitative importance of CO2 fixation by s...
TL;DR: The stochastic dual-limit model of lizard behavioral thermoregulation closely predicts the observed frequency distribution of body temperatures only when the cost for thermoreGulation is low and when there is high thermal reinforcement or high ambient temperature.
Abstract: The desert iguana (Dipsosaurus dorsalis) precisely thermoregulates in an operant conditioning apparatus, where it must walk 1 m to obtain a short-duration thermal reinforcement. The preferred body temperature depends on the duration of the thermal reinforcement (30-180 s) and on the ambient temperature (20 C or 30 C). Variation in preferred body temperature is not due to physiological constraintsexcept perhaps in the shortest-duration reinforcement at 20 C-but reflects motivational variation. The precision of thermoregulation depends on the thermal reinforcement duration, the ambient temperature, and the extent of the elevation of body temperature above ambient air temperature. The body temperature distributions were negatively skewed except under the short-duration thermal regimens. The stochastic dual-limit model of lizard behavioral thermoregulation closely predicts the observed frequency distribution of body temperatures only when the cost for thermoregulation is low (i.e., when there is high thermal ...
TL;DR: The relativelyLarge eggs of Terrapene ornata may represent the one adaptation of this species for development in terrestrial conditions, because large eggs of other turtles are more likely to hatch following incubation in a stressful hydric environment than are smaller eggs laid by conspecifics.
Abstract: Flexible-shelled eggs of the terrestrial turtle Terrapene ornata were incubated on wet (-150 kPa) and dry (-800 kPa) substrates at 29 C. Eggs on the wet medium absorbed water from the environment and increased in mass by 6% over the course of incubation, whereas eggs on the dry substrate lost water throughout development and weighed 17% less late in incubation than they did at oviposition. Availability of water to embryos had no apparent influence on hatching success, but embryos in the wet environment incubated longer, mobilized more of the nutrient reserve in their yolk, and grew larger before hatching than did those in the dry setting. Most of the ammonia released in catabolism of protein by embryonic Terrapene was detoxified by converting it to urea, which accumulated in eggs during incubation. In later stages of development urea attained concentrations inside eggs that may have been sufficient to inhibit metabolism of embryos, with the inhibition potentially being greater in dry settings than in wet ...
TL;DR: The data suggest that anaerobic metabolism can be an important pathway of energy input for lizards under natural conditions and support the hypothesis that physiological constraints can limit the behaviors available to a species of lizard.
Abstract: We measured whole-body lactic acid concentrations of two species of iguanid lizards and two species of teiids in the field during routine and experimentally manipulated activities. Lactate concentrations were lowest when lizards first emerged in the morning. Routine foraging behavior produced small increases in lactate concentrations for all species. The teiids (Cnemidophorus exsanguis and C. sonorae) had significantly higher lactate concentrations at emergence and during routine activity than did the iguanids (Sceloporus virgatus and S. jarrovi). For S. virgatus lactate concentration during routine activity was positively correlated with the distance a lizard moved (0-16 m) during the half-hour period of observation before capture. Subduing and swallowing grasshoppers increased lactate concentrations of S. virgatus by an average of .121 mg/g, which was an increase of 40% over the average for routine activity. The magnitude of the increase was positively correlated with the size of the prey (.09-.48 g) bu...
TL;DR: It is indicated that ants could tolerate temperatures >CTM for short periods and that short but frequent thermal respites facilitated ant survival at temperatures = CTM.
Abstract: Foragers were active on the insolated surface between sand surface temperatures ($T_{s}$) of 27-67 C. At $T_{s} > 51$ C foragers periodically paused in relatively cooler thermal refuges, such as by remaining in the shade or by climbing above the desert floor on any available object. The frequency and length of pauses in thermal refuges increased with increasing $T_{s}$. Workers, because of their small size (∼4 mg live mass), had low thermal inertia, as evidenced by high cooling rates in a range of air speeds, and were therefore efficient heat exchangers, equilibrating rapidly to ambient temperature. Through measurements of operative environmental temperature ($T_{e}$) in pertinent positions in the ant's habitat and a knowledge of wind-related cooling rates, it was possible to estimate the body temperature ($T_{b}$) Of foraging ants. Foragers experienced periods when $T_{b}$ would have equaled or exceeded their critical thermal maximum (CTM) of 51.5 C. Laboratory experiments indicated that ants could toler...
TL;DR: Gerbils on a restricted food intake maintained their weight after an initial loss of 7.93%.
Abstract: Average daily metabolic rates (ADMRs) were monitored under several dietary conditions. Gerbillus pusillus demonstrated a 14-h cycle of metabolic activity in phase with the photoperiod. When food and water were provided ad lib., ADMR was 96.5% of the predicted value for a granivorous rodent. When deprived of water with an ad lib. supply of food, ADMR increased significantly. Unfavorable changes in these dietary regimes result in periodic bouts of hypothermia. Gerbils on a restricted food intake maintained their weight after an initial loss of 7.93%. This negligible weight loss implies that G. pusillus uses hypothermia to regulate its metabolic rate to the energy available. During periods of torpidity, metabolic rate was directly related to both ambient and body temperature. The gerbils were unable to arouse below \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepack...
TL;DR: The acute thermal tolerances of six Daphnia species were compared at three acclimation temperatures and D. obtusa had the highest tolerance, while D. pulex had the lowest, and significant intraspecific differences in thermal tolerance were noted.
Abstract: The acute thermal tolerances of six Daphnia species were compared at three acclimation temperatures. Of the species tested, all but one showed an increase in thermal tolerance when acclimated at higher temperature. Comparison of the regression relationships between thermal tolerances and acclimation temperature revealed no significant interspecific differences among species in their improvement of thermal tolerance caused by acclimation. However, significant intraspecific differences in thermal tolerance were noted. Daphnia obtusa had the highest tolerance, while D. pulex had the lowest. Among the other species acclimated at 10 C, thermal tolerance declined in a sequence of D. ambigua, D. magna, D. carinata, and D. nivalis. The differences in thermal tolerance noted among species were correlated with maximum temperatures of the environment from which they originated. While comparison of clones of D. pulex from several geographic localities revealed up to 2 C differences in acute thermal tolerance, there w...
TL;DR: To determine what period of exposure to long-day lengths is necessary to induce photorefractoriness in the European starling (Sturnus vulgaris), intact and castrated males were first maintained on day lengths of 11L:13D per day for 20 wk, which was found to be long enough to cause maximum testicular development in intact males and maximum plasma luteinizing hormone (LH) levels in castrates.
Abstract: The breeding season of many species of birds is terminated by the onset of photorefractoriness; birds become refractory to the stimulatory effects of long-day lengths, and the gonads spontaneously regress. To determine what period of exposure to long-day lengths is necessary to induce photorefractoriness in the European starling (Sturnus vulgaris), intact and castrated males were first maintained on day lengths of 11L:13D per day for 20 wk. This day length is long enough to cause maximum testicular development in intact males and maximum plasma luteinizing hormone (LH) levels in castrates but not long enough to induce photorefractoriness. Both intacts and castrates were then divided into six groups. A control group was kept on 11 L:13D. Other groups were transferred from 11 L: 13D to 18L:6D for periods of 1, 3, 7, 14, or 21 days and then returned to 1 L: 13D. Six weeks after the treatment groups had initially been transferred to 18L:6D, all six groups were again transferred from 1 L:13D to 18L:6D to test ...
TL;DR: Rates of growth and metabolism as well as timing of metamorphosis can be precisely described using feeding rate (Cr) as the predictor in Rana tigrina and selected anurans exposed to variables of more than one environmental factor.
Abstract: Rates of growth (Pr) and metabolism (Mr) as well as timing of metamorphosis can be precisely described using feeding rate (Cr) as the predictor in Rana tigrina and selected anurans exposed to variables of more than one environmental factor. To predict size at metamorphosis in these anurans, Pr and development rate (Dr) as well as stage-specific growth (Ps) are jointly used as the predictor. Since Cr can predict Pr and Dr, one must know Cr and Ps to predict size at metamorphosis when variables of more than one environmental factor are considered.
TL;DR: The effects of exhausting exercise on acid-base balance of skipjack tuna blood were investigated and a mixed respiratory/metabolic acidosis was displayed with blood pH being reduced by ∼0.4 units.
Abstract: The effects of exhausting exercise on acid-base balance of skipjack tuna blood were investigated. Following exercise, tuna displayed a mixed respiratory/metabolic acidosis with blood pH being reduced by ∼0.4 units. The respiratory component (51% of the initial acidosis) was compensated following 20 min of recovery, while the blood metabolic acid load (H⁺m; ∼8 mM) was cleared after only 50 min. At that time, there was a great discrepancy between blood lactate load and H⁺m load because blood lactate levels were still increasing. The significance of these results is discussed with reference to the tuna's habitat, behavior, and physiology.
TL;DR: In this paper, the authors presented Arctic char with plumes of H⁺ and CO₂ and their preference/avoidance responses compared with those obtained with acidified, moderately hard water.
Abstract: Evidence from the literature suggests that fish are more responsive to CO₂ than H⁺ when these two stimuli appear together. Here Arctic char were presented with plumes of H⁺ and CO₂ and their preference/avoidance responses compared with those obtained with acidified, moderately hard water. Hydrochloric acid presented in pH 7.0 decarbonated water was attractive when plume pH exceeded 5.5 but avoided at higher concentrations down to pH 3.3. The avoidance of plumes less than pH 5.5 was not diminished by lowering ambient pH to 5.5. Carbon dioxide plumes were avoided at plume/ambient gradients greater than 50 μmol/liter but was attractive at lower concentrations. The response to acidified natural water closely followed the concentration-response curve for CO₂ but not H⁺. The results, therefore, demonstrate that fish behaviorally discriminate between H⁺ and CO₂, relying principally on the latter for orientation within H⁺/CO₂ gradients. However, fish can use H⁺ alone to avoid lethal levels of pH.