Effects of temperature on the rate of increase of Stomoxys calcitrans and Stomoxys niger niger (Diptera: Muscidae) from La Réunion island

Adult survival and reproduction were compared between two Stomoxys species that co-occur in La Reunion, the cosmopolitan Stomoxys calcitrans (L.), and the tropical Stomoxys niger niger Macquart. In a first experiment, mean longevity and fecundity were determined at five constant temperatures from 15 to 35 degrees C, after development at the same temperatures. Adult longevity was greatest at 20 degrees C in S. calcitrans and at 15 degrees C in S. niger. Adult S. niger survived longer than adult S. calcitrans, especially at 15 degrees C. At 35 degrees C, all flies died within 3 d. Reproduction occurred only within the 20-30 degrees C range, and S. niger laid more eggs than S. calcitrans. In both species, lifetime fecundity tended to decrease when temperature increased, because of the shortening of the oviposition period. In a second experiment, adults were maintained at 15 degrees C after development at 25 degrees C. The higher temperature during development significantly increased adult longevity in S. calcitrans but not in S. niger. Reproduction occurred at 15 degrees C, with notable fecundity in S. calcitrans (22 eggs per female) but not in S. niger (<1 egg per female). Using previous results on immature survival and developmental time in the two species, several life history parameters were compared at each temperature. Generation time decreased with increasing temperature and was highly similar in both species. Concurrently, the intrinsic rate of increase (r) increased with temperature from 15 to 30 degrees C. At 15 degrees C, r was higher in S. calcitrans, but within the 20-30 degrees C range, r was higher in S. niger. The results suggest 1) S. niger has evolved a strategy of survival without any reproduction during the tropical winter, in contrast with S. calcitrans that breeds more continuously; and 2) S. niger may outnumber S. calcitrans in warm areas, at least when development occurs in media of poor quality.     

Ecology of leishmaniasis in the south of France. 21. Influence of temperature on the development of Leishmania infantum Nicolle, 1908 in Phlebotomus ariasi Tonnoir, 1921. Experimental study

The influence of temperature on the life-cycle of Leishmania infantum Nicolle, 1908 (isolated from a dog in the Cévennes) in a known vector (Phlebotomus ariasi Tonnoir, 1921) was studied with special reference to the proportion of flies infected and the intensity and localization of parasites in the sandfly. Wild female sandflies were caught at night by active searches and were put with a heavily infected dog in a mosquito net on the night of capture. On the following morning, engorged females were tubed individually and were then maintained at 10, 15, 20, or 25 degrees C (+/- 1.5 degrees). The temperatures were chosen after preliminary experiments which showed that temperatures of 30 degrees C or less than 5 degrees C were lethal to both the sandfly and, usually, the parasite. Midguts of the flies were dissected and examined 6 to 10 days after the infective feed. Although there were no obvious differences in the proportions of infected sandflies at different temperatures, a statistical analysis of the finding (chi 2 test) showed that raising the temperature: significantly increased the overall proportion of infected sandflies; speeded up the multiplication of promastigotes in the midgut; controlled the movement of parasites forwards into the thoracic midgut (from 15 degrees C); encouraged the attachment of the flagellates to the wall of the stomodaeal valve (from 20 degrees C). The use of an exponential model to deduce the size of the parasite population at the different temperatures led to the conclusion that the optimum temperature for L. infantum is in the region of 25 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dormancy, embryogenesis, and hatching of eggs of Prosimulium kiotoense (Diptera: Simuliidae) under natural and experimental conditions.

The egg dormancy and embryogenesis of the univoltine black fly, Prosimulium kiotoense Shiraki, in southwestern Japan were examined under natural and laboratory conditions. Eggs laid in April remained dormant until August (approximately 14 wk after oviposition). Hatching commenced in early October (after 23 wk), when air and water temperatures decreased to 20 and 15 degrees C, respectively, and continued until mid-December (32 wk) in the field. Laboratory experiments showed that lower temperatures (10 and 14 degrees C) supported embryogenesis similar to that observed in the field. In contrast, higher temperatures (18 and 22 degrees C) retarded or completely suppressed embryogenesis after the termination of dormancy. However, completion of dormancy was accelerated when eggs were exposed experimentally to these higher temperatures for 3-12 wk, then returned to a constant low temperature (14 degrees C). Daylength did not affect the maintenance and termination of dormancy. Therefore, temperature played an important role differentially affecting completion of dormancy and postdormancy development. Variable lengths of developmental periods among egg batches under the same conditions indicated possible genetic control of dormancy intensity.     

Independence of brain and body temperatures in flying American kestrels, Falco sparverius.

Brain and body temperatures were measured via small thermocouples implanted in the anterior hypothalami and colons, respectively, of five adult American kestrels (F. sparverius, mean mass 119 g) during descending flights in a wind tunnel at angles of 4 and 6 degrees below horizontal, at 10 m.s-1 air speed, and at 23 degrees C air temperature. For comparison, temperatures were recorded from resting birds at 22.5-36.1 degrees C air temperatures. Colonic (Tc) and hypothalamic (Th) temperatures both increased after the onset of flight; steady-state levels were attained after 1 min in the hypothalamus and after 5 or more min in the colon. The steady-state difference (delta T = Tc - Th) averaged 1.2 degrees C, higher by 0.5 degrees C than delta T in resting kestrels. The establishment of delta T during flight may be correlated with increased respiratory and corneal evaporation. The response apparently confines most stored body heat to noncranial regions, thus protecting brain tissue from thermal extremes.     

Diel changes in adult mosquito microhabitat temperatures and their relationship to the extrinsic incubation of arboviruses in mosquitoes in Kern County, California

Microhabitat temperatures experienced by nocturnally active Culex tarsalis Coquillett mosquitoes were measured in the southern San Joaquin Valley of California. Temperatures of the diurnal resting shelter and nocturnal activity air space were measured by digital recorder at three Cx. tarsalis habitats in Kern County. Temperatures measured by digital recorders agreed well with temperatures recorded concurrently at nearby California Irrigation Management and Inspection System weather stations. Monthly temperatures among habitats were combined to depict the diel temperature regimen experienced by female Cx. tarsalis as a consequence of daily movement between the diurnal resting shelter and nocturnal air space. Transitions between the two microhabitats corresponded to the times of mosquito ingress and egress (i.e., sunrise and sunset). The composite daily temperature mean ranged from 7.4 degrees C in December to 21.5 degrees C in July, and temperature extremes seldom exceeded a daily maximum of 25.0 degrees C during the summer or dropped below a daily minimum of 5.0 degrees C during the winter. Overall, mosquitoes occupied a composite thermal environment where the extrinsic incubation of an arbovirus would have occurred at ambient temperatures that were cooler than either the diurnal resting shelter or activity air space.     

Temperature measurement artefacts of thermocouples and fluoroptic probes during laser irradiation at 810 nm.

This study examined the artefact induced in temperature measurements made with thermocouples and Luxtron fluoroptic probes in the presence of infrared radiation. Localized heating was created using a continuous-wave, 810 nm diode laser system emitting 2.0 W from a cylindrical diffusing optical fibre, in air, water and an agar-albumin phantom. The temperature was measured every 1.0 s for 10 to 150 s, with both a thermocouple and a Luxtron fluoroptic probe at distances of 2, 3, 4, 5, 6 and 7 mm from the cylindrical diffusing tip. In all cases, the fluoroptic probe recorded a higher temperature than the thermocouple during laser irradiation. The difference in measured temperatures between the Luxtron probe and the thermocouple ranged from 1.6 degrees C to 18.8 degrees C in air, from 0.3 degrees C to 10.2 degrees C in water, and from 1.4 degrees C to 10.1 degrees C in phantom, depending on the distance of the probe from the laser source. The results suggest that in the presence of laser irradiation, self-heating of the Luxtron probe induces a significant artefact in temperature measurements at distances less than 4 mm from the source fibre. As a result, fluoroptic probes may not be suitable for monitoring tissue temperature for treatments when laser irradiation is present if sensors are located close to the fibre tip (<4 mm).     

The use of trans-vinylene formation in quantifying the spatial distribution of electron beam penetration in polyethylene. Single-sided,double-sided and shielded irradiation

The use of the quantification of trans-vinylene unsaturations in irradiated ultrahigh molecular weight polyethylene (UHMWPE) in determining the spatial distribution of electron beam penetration was investigated. UHMWPE was irradiated with a 10MeV linear electron beam accelerator to 100kGy at both room temperature and 125 degrees C in air. The irradiation was carried out in shielded and unshielded single-sided and unshielded double-sided irradiation modes. Dose-depth profiles were measured by quantifying the yields of trans-vinylene unsaturations as a function of depth away from the e-beam incidence surfaces using infrared spectroscopy. The extent of beam penetration increased with increasing irradiation temperature as was manifested by the increase in the iso-dose penetration with the unshielded single-sided irradiation and increased dose overlap with the unshielded double-sided irradiation. The optimum thickness with maximum uniformity in dose-depth distribution for double-sided irradiation was 85 and 90mm for 25 degrees C and 125 degrees C irradiation temperatures, respectively.     

Brain and arterial blood temperatures of free-ranging oryx (Oryx gazella)

We used implanted miniature data loggers to measure brain and arterial blood temperatures every 5 min for up to 15 days in four free-ranging oryx ( Oryx gazella) in their natural habitat. Globe temperatures exceeded 45 degrees C and average peak radiant heat load was 800 W.m(-2). Arterial blood temperature exhibited a moderate amplitude nychthemeral rhythm of 1.8+/-0.3 degrees C (mean +/-SD). The amplitude of the nychthemeral rhythm was not influenced by variations in ambient heat load. Average brain temperature exceeded carotid arterial blood temperature by 0.29 degrees C but there was a range of body temperatures over which the brain could be up to 0.4 degrees C cooler or 0.5 degrees C warmer than arterial blood. At high body temperatures (>39.5 degrees C) at rest, three of the animals tended to maintain the brain cooler than arterial blood. During exercise the brain was always warmer than arterial blood. The slope of the regression line relating brain temperature to carotid blood temperature was less than one. At short time scales of 5-20 min, brain temperature varied significantly more than did carotid blood temperature. We attribute part of the variability in brain temperature to transient stress responses and the influence of sympathetic activation attenuating selective brain cooling. We conclude that, contrary to the widely cited postulate, the carotid rete does not protect the brain during hyperthermia. Oryx also do not show adaptive heterothermy and, over short time intervals, have a brain temperature more variable than carotid blood temperature.     

Age,Size, and Growth of the Turkish Endemic Frog Pelophylax Caralitanus (Anura: Ranidae)

Pelophylax caralitanus is a medium‐sized frog that is endemic to the upland Lake District of south‐central Turkey and currently identified as a threatened species as a result of overharvesting and habitat modification. In this report, demographic data are provided for four major lakeside populations of this species based on a skeletochronological analysis of bone growth in large samples of frogs that were captured and released during 2011 and 2013. Adult males (aged 2–9 years) and females (aged 2–10 years) ranged in size from 66 to 105 mm snout‐vent length (SVL) and 65 to 110 mm SVL, respectively, and typically attained sexual maturity in their second (low‐elevation sites) or third (high‐elevation sites) summer of growth following metamorphosis. The four populations exhibited differences in growth rate and age at sexual maturity, which appeared to reflect differences in the average monthly temperature and length of the growth season rather than elevation per se, that is, warmer temperatures and longer growth seasons resulted in smaller adults. All populations had a similar overall age structure, with approximately equal frequencies of individuals in the five age and size classes following maturity. Anat Rec, 301:1224–1234, 2018. © 2017 Wiley Periodicals, Inc.     

The effect of intraventricular injections of noradrenaline, 5-hydroxytryptamine, acetylcholine and tranylcypromine on the ox (Bos taurus) at different environmental temperatures

1. Noradrenaline, 5-hydroxytryptamine (5-HT), acetylcholine and tranylcypromine were injected or infused into the lateral ventricle of the ox. The effects of these drugs on heart and respiration rates, heat production, rectal, skin and hypothalamic temperatures and skin evaporative loss were measured when the animal was exposed to environmental temperatures ranging from -1 degrees C to +30 degrees C.2. Acetylcholine (0.001-2 mg) had no detectable effect on temperature regulation at 20 degrees C.3. In small doses (0.005-0.05 mg) 5-HT had no detectable effect. Larger doses (2-5 mg) given in a cold environment (-1 degrees C) also had no effect but the same doses given in warm environments (15-30 degrees C) caused increases in skin temperatures, skin evaporative loss and respiratory rate, and decreases in rectal and hypothalamic temperatures.4. Infusion of tranylcypromine (0.107 ml./min of a 1 in 50 solution) in a warm environment (20 degrees C) also caused a decrease in rectal temperature after a delay of 1-1(1/2) hr during which no effects were apparent.5. Noradrenaline (2 mg) had no effect on temperature regulation when injected into animals in a warm environment (30 degrees C). When injected (1 mg) into animals in a cold environment (-1 degrees C) shivering stopped and heat production and rectal and hypothalamic temperatures were decreased.6. It is concluded that intraventricular 5-HT and noradrenaline both cause a decrease in body temperature, and it is unlikely that central temperature regulation in the ox is mediated only by these two substances.     

Abiotic parameters and diel and seasonal activity of Borrelia-infected and uninfected Ixodes persulcatus (Acarina: Ixodidae)

During the 1997 season of Ixodes persulcatus Schulze tick activity, 579 specimens were collected by flagging in the vicinity of St. Petersburg (Morskaja, Lisy Nos). Collections were made from April to July, and at each collection time the following measurements were recorded: light intensity (in lux); temperature of soil 1-1.5 cm below leaf litter, at the soil surface, and in the air 1.5 m above the soil surface; and relative humidity. The gradient between soil at a depth of 1-1.5 cm and soil surface temperatures appeared to be the main physical parameter that initiated tick migration out of the leaf litter. At soil temperature intervals of 5-10 degrees C and 21-26 degrees C, ticks were found only when the soil temperature 1-1.5 cm below the soil surface was colder than at its surface. When temperature ranged from 11 to 20 degrees C, 24% of the ticks were collected when the surface temperature was colder than that below the soil surface. Sixty percent of the ticks, especially nymphs, were collected when the soil surface and subsoil temperature difference ranged from 0 to 2.0 degrees C. The gradient between soil temperature and relative humidity appeared to increase the importance of the gradient between the soil and surface temperature at which time the maximum number of ticks were caught. Borrelia burgdorferi sensu lato infected ticks were collected only after 1100 hours. Prior to and just after 1100 h the mean difference between soil temperatures was 4.7 degrees C, whereas the mean difference between soil and surface temperatures was 6.4 degrees C at this time. The most important factors that influenced the appearance of Borrelia-infected ticks were the temperature gradients that existed between the surface and soil temperatures and the soil and air relative humidity. Greater numbers of infected nymphs were collected when temperature intervals ranged from 10 to 14 degrees C and lower numbers were collected between 15 and 20 degrees C. No Borrelia-infected nymphs were captured when the temperature interval ranged from 21 to 26 degrees C. Infected adults appeared to be more tolerant of higher temperatures than Borrelia-infected nymphs. A significant relationship was found between the activity of Borrelia-infected I. persulcatus and the temperature of the air, soil below the surface, at the soil surface, and relative humidity.     

Transurethral ultrasound applicators with directional heating patterns for prostate thermal therapy: in vivo evaluation using magnetic resonance thermometry

A catheter-based transurethral ultrasound applicator with angularly directional heating patterns has been designed for prostate thermal therapy and evaluated in canine prostate in vivo using MRI to monitor and assess performance. The ultrasound transducer array (3.5 mm diameter tubular transducers, 180 degrees active sectors, approximately 7.5 MHz) was integrated to a flexible delivery catheter (4 mm OD), and encapsulated within an expandable balloon (35 mm x 10 mm OD, 80 ml min(-1) ambient water) for coupling and cooling of the prostatic urethra. These devices were used to thermally coagulate targeted portions of the canine prostate (n = 2) while using MR thermal imaging (MRTI) to monitor the therapy. MRI was also used for target definition, positioning of the applicator, and evaluation of target viability post-therapy. MRTI was based upon the complex phase-difference mapping technique using an interleaved gradient echo-planar imaging sequence with lipid suppression. MRTI derived temperature distributions, thermal dose exposures, T1-contrast enhanced MR images, and histology of sectioned prostates were used to define destroyed tissue zones and characterize the three-dimensional heating patterns. The ultrasound applicators produced approximately 180 degrees directed zones of thermal coagulation within targeted tissue which extended 15-20 mm radially to the outer boundary of the prostate within 15 min. Transducer activation lengths of 17 mm and 24 mm produced contiguous zones of coagulation extending axially approximately 18 mm and approximately 25 mm from base to apex, respectively. Peak temperatures around 90 degrees C were measured, with approximately 50 degrees C-52 degrees C corresponding to outer boundary t43 = 240 min at approximately 15 min treatment time. These devices are MRI compatible, and when coupled with multiplanar MRTI provide a means for selectively controlling the length and sector angle of therapeutic thermal treatment in the prostate.     

Temperature effects on development and survival of two stable flies, Stomoxys calcitrans and Stomoxys niger niger (Diptera: muscidae), in La Réunion Island

Two stable fly species, Stomoxys calcitrans (L., 1758) and Stomoxys niger niger Macquart, 1851, co-occur in La Reunion, where they are important pests of cattle. The survival and developmental rate of the immature stages were compared at five constant temperatures from 15 to 35 degrees C. In both species, immature survival was highest at 20-25 degrees C and markedly decreased at 15 and 35 degrees C. At the lower temperatures, mortality was observed mainly for S. calcitrans larvae and S. niger eggs. At the higher temperatures, mainly pupae of both species died. At all temperatures, S. calcitrans survived better than S. niger. Developmental time was highly similar in both species, decreasing from 71 d at 15 degrees C to 13 d at 30 degrees C in S. calcitrans and from 69 d at 15 degrees C to 14 d at 30 degrees C in S. niger. Developmental times increased slightly at 35 degrees C. Surprisingly, the tropical S. niger developed slightly faster than the cosmopolitan S. calcitrans at 15-20 degrees C; the reverse was found at higher temperatures. Temperature summation models confirmed that S. niger had a lower developmental threshold than S. calcitrans (11.3 versus 12.2 degrees C) and higher day-degree (DD) requirements to complete development (251 versus 225 DD). Overall, the results suggest that S. calcitrans is better adapted than S. niger, in terms of adult production from eggs, in the temperature range of La Reunion.     

Aspergillus hyphae in infected tissue: evidence of physiologic adaptation and effect on culture recovery

Microbiologic cultures of fungi are routinely incubated at ambient temperatures in room air, and the rate of recovery of Aspergillus species from clinical specimens is poor. Failure of current culture methods to mimic the physiologic temperature and low-oxygen environment found in hypha-laden infected tissue may underlie this poor recovery. Experiments were performed to compare the recovery of Aspergillus spp. incubated at 35 degrees C in 6% O(2)-10% CO(2) with that at 25 degrees C in room air. The samples tested included Aspergillus-infected tissue specimens from a dog model and human autopsies, experimental anaerobically stressed Aspergillus inocula, and 10,062 consecutive clinical specimens. Culture at 35 degrees C in 6% O(2)-10% CO(2) significantly enhanced the recovery of Aspergillus spp. from the infected autopsy tissue samples. Incubation at 35 degrees C alone resulted in approximately 10-fold-improved culture recovery from the experimentally stressed hyphae, and the 6% O(2)-10% CO(2) atmosphere independently favored growth under temperature-matched conditions. Finally, incubation at 35 degrees C (in room air) improved the overall recovery of Aspergillus spp. from clinical specimens by 31%. Culture at 35 degrees C in a microaerobic atmosphere significantly enhances the recovery of Aspergillus spp. from various sources. Aspergillus hyphae growing in infected tissue appear to be adapted to the physiologic temperature and hypoxic milieu.     

Temperature effects on ventilation and acid-base balance of the green turtle

Ventilation (VE), pulmonary gas exchange (MO2 and MCO2), and arterial acid-base status (pH and PaCO2) were measured in immature green turtles. Chelonia mydas, equilibrated at 15, 25, and 35 degrees C. From 25 to 35 degrees C, pH decreased by 0.0134 U/degrees C and PaCO2 increased from 30.1 +/- 1.1 to 46.0 +/- 2.4 Torr (mean +/- SE, n = 8) in conformity with results from other ectotherms. From 15 to 25 degrees C, however, pH fell on the average by 0.06 U/degrees C but the change was not significant. PaCO2 rose over this range from 25.3 +/- 1.6 to 30.1 +/- 1.1 Torr. Calculated plasma [HCO3-], 27-28 meq/l, did not change over the entire temperature range. Both VE and MO2 increased with temperature, but the ratio, VE/MO2 (the air convection requirement), fell with temperature (1.01 +/- 0.10 l/mmol at 35 degrees C, 0.64 +/- 0.03 l/mmol at 25 degrees C, and 0.45 +/- 0.04 l/mmol at 15 degrees C). We conclude that the green turtle adheres to the typical ectotherm blood acid-base pattern over their usual temperature range (25-35 degrees C), but that pH control deviates from this pattern at temperatures below this range.     

Bonding behavior between two bioactive ceramics in vivo

The purpose of this study is to examine the chemical bonding mechanism between bioactive ceramics in vivo. Two experiments were performed. In the first experiment, rectangular specimens (5 mm X 5 mm X 25 mm) of apatite-wollastonite containing glass-ceramics (designated A.W-GC) were used. In the second experiment, plates (15 mm X 10 mm X 2 mm) of A.W-GC and three types of hydroxyapatite (designated HA) were used. The sintering temperature and porosity (%) of the three types of HA were 1200 degrees C (0.4%), 1000 degrees C (4.8%), and 800 degrees C (45%), respectively. In each experiment, two pairs of specimens of identical material, one bound with silk thread, the other not bound, were implanted subcutaneously into rats. In the first experiment, bonding of only bound specimens was observed at 3 and 6 months after implantation. The observation of interface by SEM-EPMA showed that a Ca-P-rich layer formed between the two specimens. In the second experiment, bonding of both bound and nonbound A.W-GC produced identical results 1 month after implantation. For HA sintered at 800 degrees C and 1000 degrees C, bonding was observed in every specimen. This phenomenon might be caused by the chemical change of hydroxyapatite occurring at different sintering temperatures. The Ca-P-rich layer was observed between two plates. These results suggest that self-repair of bioactive ceramic is possible under certain conditions.     

Temperature-dependent development and survival rates of Culex quinquefasciatus and Aedes aegypti (Diptera: Culicidae)

Development, growth, and survival of Culex quinquefasciatus Say and Aedes aegypti (L.) were determined at six constant temperatures (15, 20, 25, 27, 30, 34 degrees C). The Sharpe & DeMichele four-parameter model with high-temperature inhibition described the temperature-dependent median developmental rates of both mosquito species. In both species, body size generally decreased as temperature increased. Head capsule widths in all instars in both species were significantly greater at 15 than at 30-34 degrees C. Except for the third instar of Ae. aegypti, the larval body lengths in both species were significantly greater at 15 than at 34 degrees C. All instars and pupae of both species and the adults in Cx. quinquefasciatus were significantly heavier at 15 than at 27-34 degrees C. In Cx. quinquefasciatus, survival from eclosion to adult emergence was highest in the range from 20 to 30 degrees C (85-90%) and dropped drastically at 15 (38%) and 34 degrees C (42%). In Ae. aegypti, survival to adult stage was high at 20 (92%) and 27 degrees C (90%) and lowest at 15 degrees C (3%).     

Optimal survival of Helicobacter pylori under various transport conditions.

The ability of clinical isolates and type strains of Helicobacter pylori to survive in Stuart transport medium, isotonic saline solution, and urea-containing isotonic saline was evaluated. The influences of temperature (4, 10, 15, 20, and 30 degrees C) and holding time (6 to 48 h) and the effect of exposure to air on survival were also studied. The recovery rate of H. pylori was highest from Stuart transport medium in comparison with the recoveries from the other transport media tested. We found that at holding temperatures above 15 degrees C the organisms became noncultivable within 6 h or less, while they survived for 2 days or longer at 10 degrees C. The presence of urea at a concentration of 2% (wt/vol) in isotonic saline resulted in the loss of viability of the organisms tested.     

Metabolism and temperature regulation in young harbor seals Phoca vitulina richardi.

Metabolism and the ability to regulate core and peripheral temperatures under a variety of ambient conditions were studied in five unrestrained pups (less than 5 wk old) and four 3- to 5-mo-old harbor seals. Pups born with nonlanugo (adultlike) hair and little fat were able to swim in 5 degrees C water for several hours without becoming hypothermic. They were also found to tolerate 5 degrees C air temperature with the fur wet and exposed to a 35-knot wind. Basal metabolism in pups averaged 0.8 ml O2 g-1 h-1, which is 2.6 times the predicted value for an adult mammal of the same weight. Lower critical temperature in air was about 3 degrees C. Oxygen uptake in 3- to 5-mo-old seals under basal conditions was 0.5 ml g-1 h-1. Minimal thermal conductance values were .02 and .015 ml O2 g-1 h-1 degrees C-1 in pumps and 3- to 5-month-old seals, respectively. Appendages, and to a lesser extent the skin on the torso, cooled appreciably at lower air temperatures, and the flippers were kept just above freezing in subzero air. Tissue insulation provided by low peripheral temperatures and a high resting metabolic rate enable newborn and developing harbor seals to tolerate the low temperatures encountered in their natural environment.     

Advantages of smaller body mass during distance running in warm, humid environments

The purpose of this study was to examine the extent to which lighter runners might be more advantaged than larger, heavier runners during prolonged running in warm humid conditions. Sixteen highly trained runners with a range of body masses (55-90 kg) ran on a motorised treadmill on three separate occasions at 15, 25 or 35 degrees C, 60% relative humidity and 15 km x h(-1) wind speed. The protocol consisted of a 30-min run at 70% peak treadmill running speed (sub-max) followed by a self-paced 8-km performance run. At the end of the submax and 8-km run, rectal temperature was higher at 35 degrees C (39.5+/-0.4 degrees C, P<0.05) compared with 15 degrees C (38.6+/-0.4 degrees C) and 25 degrees C (39.1+/-0.4 degrees C) conditions. Time to complete the 8-km run at 35 degrees C was 30.4+/-2.9 min (P<0.05) compared with 27.0+/-1.5 min at 15 degrees C and 27.4+/-1.5 min at 25 degrees C. Heat storage determined from rectal and mean skin temperatures was positively correlated with body mass (r=0.74, P<0.0008) at 35 degrees C but only moderately correlated at 25 degrees C (r=0.50, P<0.04), whereas no correlation was evident at 15 degrees C. Potential evaporation estimated from sweat rates was positively associated with body mass (r=0.71, P<0.002) at 35 degrees C. In addition, the decreased rate of heat production and mean running speed during the 8-km performance run were significantly correlated with body mass (r=-0.61, P<0.02 and r=-0.77, P<0.0004, respectively). It is concluded that, compared to heavier runners, those with a lower body mass have a distinct thermal advantage when running in conditions in which heat-dissipation mechanisms are at their limit. Lighter runners produce and store less heat at the same running speed; hence they can run faster or further before reaching a limiting rectal temperature.