Physiological zoology最新文献

{"title":"Metabolic reserves and evolved stress resistance in Drosophila melanogaster.","authors":"M Djawdan,&nbsp;A K Chippindale,&nbsp;M R Rose,&nbsp;T J Bradley","doi":"10.1086/515963","DOIUrl":"https://doi.org/10.1086/515963","url":null,"abstract":"<p><p>We have examined starvation and desiccation resistance in 43 outbred populations of Drosophila melanogaster that have diverged from a common ancestral population as a result of a variety of defined selection protocols. The populations differ up to 8.5-fold in desiccation resistance and up to 10-fold in starvation resistance. We used these populations to search for evolved physiological changes that might explain the differences in stress resistance. We examined two hypotheses for increased stress resistance that had been proposed previously in the literature: (1) that increments in starvation resistance are principally the result of differential lipid accumulation, and (2) that changes in glycogen accumulation play a role in evolved increases in resistance to desiccation stress. By quantifying desiccation resistance, starvation resistance, lipid content, and carbohydrate content in each of our populations of flies, we were able to demonstrate strong correlations between the capacity of the flies to resist starvation and the quantity of lipid or carbohydrate that the flies had stored. The strongest correlation (R2 = 0.99) was observed when the total energy content of both the lipid and carbohydrate stores was regressed against starvation resistance. These results demonstrate that the flies responded to selection for starvation resistance through a genetically determined increase in both lipid and carbohydrate storage. Similar analyses of the correlation between lipid storage or total energy storage and desiccation resistance revealed no significant correlations. Carbohydrate storage was significantly correlated with desiccation resistance in female but not in male flies. These results suggest that different forms of stress are resisted with distinct physiological mechanisms and that the evolutionary response of the flies to stress selection is specific to the stress imposed.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 5","pages":"584-94"},"PeriodicalIF":0.0,"publicationDate":"1998-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515963","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20668817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Charlotte Preston Mangum","authors":"L. Burnett, P. Defur","doi":"10.1086/515947","DOIUrl":"https://doi.org/10.1086/515947","url":null,"abstract":"","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 1","pages":"469 - 595"},"PeriodicalIF":0.0,"publicationDate":"1998-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515947","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60422995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The energetics of male reproduction in an aquatically mating pinniped, the harbour seal.","authors":"D W Coltman,&nbsp;W D Bowen,&nbsp;S J Iverson,&nbsp;D J Boness","doi":"10.1086/515418","DOIUrl":"https://doi.org/10.1086/515418","url":null,"abstract":"<p><p>The energy expenditure of breeding male harbour seals, Phoca vitulina, on Sable Island, Nova Scotia, was investigated by measuring changes in body mass, body composition, and water flux using isotope dilution. Seals lost 0.47% +/- 0.04% (n = 34) of their initial mass per day during the breeding season (4 wk), and fat, water, and protein accounted for 64.3% +/- 4.8%, 27.8% +/- 3.3%, and 6.9% +/- 1.4% of this mass loss, respectively (n = 31). Total energy expenditure was estimated as 33.3 +/- 1.9 MJ d(-1), or 3.9 +/- 0.2 W kg(-1) (n = 17), similar to rates measured in terrestrially mating pinniped species. However, unlike terrestrially mating pinnipeds, male harbour seals did not fast during the breeding season, and energy intake from foraging accounted for 61.8% +/- 4.0% of the total energy expended. Males derived most of their expended energy from food intake early in the breeding season. However, as oestrus females became increasingly available, reduced rates of food intake in males were coupled with increased rates of total energy expenditure. Larger males expended significantly more energy from body stores and more total energy than smaller males. Male harbour seals appeared to balance the energetic costs of reproduction against the constraints of small body size by foraging during deep-diving trips before the appearance of oestrus females and by opportunistic feeding throughout the breeding season while at sea. We suggest that size dimorphism may be less pronounced in aquatically mating pinnipeds partly because the temporal and spatial separation of foraging and reproduction is less distinct than it is for terrestrially breeding pinnipeds.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"387-99"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515418","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20596261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of hypervolemia and hypovolemia on cardiac and posterior lymph heart function in the toad Bufo marinus (L.).","authors":"J G Williams,&nbsp;J M Jones,&nbsp;D P Toews","doi":"10.1086/515422","DOIUrl":"https://doi.org/10.1086/515422","url":null,"abstract":"<p><p>Cardiac and posterior lymph heart function in the toad Bufo marinus (L.) were measured in response to hemorrhage and both systemic and lymphatic volume loading to evaluate the role of the amphibian lymphatic system in fluid regulation. In every animal, systemic volume loading elicited an initial sharp rise in mean arterial blood pressure, corresponding to an immediate cessation of lymph heart contraction lasting approximately 12 min. This was followed by a short-term decrease in blood pressure, to 36% below normal. While stroke volume and lymph flow for the individual animals increased variably over a 6-h period, mean lymph heart rate and pressure varied little. Lymphatic volume loading elicited only minor changes in blood heart and lymph heart rate. Again, stroke volume and lymph flow increased variably, with the effect lasting about 13 h. Hypovolemia caused a sharp drop in blood pressure and a corresponding rise in blood heart rate. Lymph heart variables changed little, with the exception of rate, which, in some animals, was elevated for approximately 20 min following hemorrhage.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"458-68"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515422","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20595519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intrapopulation variation in ecological energetics of the garter snake Thamnophis sirtalis, with analysis of the precision of doubly labeled water measurements.","authors":"C C Peterson,&nbsp;B M Walton,&nbsp;A F Bennett","doi":"10.1086/515426","DOIUrl":"https://doi.org/10.1086/515426","url":null,"abstract":"<p><p>The evolution of energetics must begin with variation within populations in ecologically realized rates of energy acquisition and expenditure. We measured aspects of field energy budgets (including metabolic rates, feeding rates, and growth rates) in a large sample of free-living garter snakes (Thamnophis sirtalis) from a single temperate/mesic population in northwestern California during their summer active season. We then analyzed interindividual variation for correlations among variables and patterns attributable to body size and sex. Field metabolic rates (measured with use of doubly labeled water) scaled in direct proportion to body mass. These rates of field energy expenditure were higher (both in absolute terms and in relation to resting metabolic rates) than those previously measured in snakes and iguanian lizards and were similar to those reported for highly active, widely foraging scincomorphan lizards. Feeding rates (as indexed by water influx rates) and growth rates were correspondingly high compared to those of other squamate reptiles. We found considerable residual variation in all measured variables not attributable to body size. Effects of sex were detected for water influx and growth rates (females > males), but not for field metabolic rate. Individual field metabolic rate was apparently consistent (repeatable) over time, water influx rate was not, and individual growth rates were strongly negatively correlated over two sequential time periods. We were unable to detect convincing correlations between any individual measures of field energetics and any commonly measured, standard laboratory measurements of oxygen consumption (standard metabolic rate at two body temperatures and maximal oxygen consumption for exercise) made on the same individuals. However, body-size-independent field rates of energy expenditure, energy intake, and growth were strongly and positively intercorrelated among individuals. We attribute these patterns to an overriding effect of costs associated with digestion and growth on field energetics, such that individual snakes that were effective foragers achieved high feeding rates and, hence, high growth rates, but also incurred high costs of growth and digestion that largely determined field metabolic rate.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"333-49"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515426","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20595749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effects of chronic hypoxia on the acute adrenergic stress response in the rainbow trout (Oncorhynchus mykiss).","authors":"C J Montpetit,&nbsp;S F Perry","doi":"10.1086/515420","DOIUrl":"https://doi.org/10.1086/515420","url":null,"abstract":"<p><p>We have investigated the effects of chronic hypoxia on the acute adrenergic stress response of adult rainbow trout (Oncorhynchus mykiss). The goal of this study was to determine whether a prior 5-d exposure of fish to lowered environmental oxygen levels (60 or 80 Torr) would influence the nature of catecholamine secretion from chromaffin tissue in situ. Using a saline-perfused posterior cardinal vein preparation, it was demonstrated that the basal (unstimulated) secretion of noradrenaline and adrenaline was increased at 60-Torr hypoxia. In response to cholinergic (carbachol-elicited) stimulation, noradrenaline and adrenaline secretion were significantly affected by prior exposure to hypoxia. The construction of dose response curves revealed that noradrenaline secretion was enhanced at the lowest doses of carbachol (1 - 5 x 10(-7) mol kg(-1)) and that this was reflected by an approximate 10-fold reduction in the ED50 (the dose of carbachol eliciting half-maximal noradrenaline secretion). The effect of chronic hypoxia on in situ carbachol-evoked adrenaline secretion was similar but less pronounced. The results of this study suggest that during chronic moderate hypoxia, increased basal catecholamine secretion and enhanced responsiveness of chromaffin cells to cholinergic stimulation, as well aiding the ongoing stress, may assist the physiological adaptations to subsequent bouts of more severe acute stress.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"377-86"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515420","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20595752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Is there a significant gas exchange through the skin of the shrew Crocidura russula monacha?","authors":"H Mover-Lev,&nbsp;H Minzberg,&nbsp;A Ar","doi":"10.1086/515424","DOIUrl":"https://doi.org/10.1086/515424","url":null,"abstract":"<p><p>Because of its small body mass, the shrew Crocidura russula monacha has a relatively high surface area to volume ratio, thin skin, and high thermal conductance compared with larger mammals. This study was aimed at examining the possibility that such a mammal may exhibit a significant skin gas exchange. Gas composition was measured in subcutaneous gas pockets. CO2 and O2 exchange through skin were measured both in vitro and in vivo. In 7-wk-old gas pockets, the steady-state PO2 and PCO2 values were 50 Torr (where 1 Torr = 133.322 Pa) and 35 Torr, respectively, compared with PO2 and Pco2 values of 73 Torr and 33 Torr, respectively, in 1-wk-old gas pockets. These changes are attributed to an increased capillary density and a decreased skin thickness after 7 wk. There was no significant gas exchange through skin during in vitro measurements. In vivo measurements indicated that O2 uptake was 0.5% and CO2 loss was 0.9% of total body metabolism at 20 degrees C. At 35 degrees C, skin O2 uptake and CO2 loss increased to 1.3% and 2.9%, respectively. These values are only part of the expected skin metabolism; thus, the rest must come from blood. Because gas exchange through the skin of this shrew is within the range of other mammals, the relatively low PCO2 and high PO2 in the gas pockets is better explained by the relative hyperventilation state exhibited by this shrew.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"407-13"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515424","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20596263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Capillarity and fibre types in locomotory muscles of wild yellow-legged gulls (Larus cachinnans).","authors":"J R Torrella,&nbsp;V Fouces,&nbsp;J Palomeque,&nbsp;G Viscor","doi":"10.1086/515425","DOIUrl":"https://doi.org/10.1086/515425","url":null,"abstract":"<p><p>This study analyzes the capillarity and fibre-type distribution of six locomotory muscles of gulls. The morphological basis and the oxygen supply characteristics of the skeletal muscle of a species with a marked pattern of gliding flight are established, thus contributing to a better understanding of the physiology of a kind of flight with low energetic requirements. The four wing muscles studied (scapulotriceps, pectoralis, scapulohumeralis, and extensor metacarpi) exhibited higher percentages of fast oxidative glycolytic fibres (>70%) and lower percentages of slow oxidative fibres (<16%) than the muscles involved in nonflight locomotion (gastrocnemius and iliotibialis). Capillary densities ranged from 816 to 1,233 capillaries mm(-2), having the highest value in the pectoralis. In this muscle, the fast oxidative glycolytic fibres had moderate staining for succinate dehydrogenase and relatively large fibre sizes, as deduced from the low fibre densities (589-665 fibres mm(-2)). All these findings are seen as an adaptive response for gliding, when the wing is held outstretched by isometric contractions. The leg muscles studied included a considerable population of slow oxidative fibres (>14% in many regions), which suggests that they are adapted to postural activities. Regional variations in the relative distributions of fibre types in muscle gastrocnemius may reflect different functional demands placed on this muscle during terrestrial and aquatic locomotion. The predominance of oxidative fibres and capillary densities under 1,000 capillaries mm(-2) in leg muscles is probably a consequence of an adaptation for slow swimming and maintenance of the posture on land rather than for other locomotory capabilities, such as endurance or sprint activities.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"425-34"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515425","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20596267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Protein use and muscle-fiber changes in free-ranging, hibernating black bears.","authors":"D B Tinker,&nbsp;H J Harlow,&nbsp;T D Beck","doi":"10.1086/515429","DOIUrl":"https://doi.org/10.1086/515429","url":null,"abstract":"<p><p>Studies of the metabolic and physiological changes that bears undergo during hibernation have, for the most part, supported the paradigm that bears use only fatty tissues as a metabolic substrate during hibernation. This study was performed to document the extent of protein loss and alteration of muscle-fiber characteristics of selected muscles in black bears during winter dormancy. Muscle biopsies were removed from the gastrocnemius and biceps femoris from seven free-ranging female black bears on the Uncompahgre Plateau in west-central Colorado. Six of the seven bears produced cubs during the hibernating season. Muscle samples were collected from the left hind limb shortly after bears entered their dens (fall), and additional samples were collected from the right hind limb just prior to bears leaving their dens (spring). Protein concentration, fast- and slow-twitch muscle-fiber ratios and muscle-fiber cross-sectional areas, and citrate synthase activity were measured in the laboratory. While protein concentration decreased in both muscles during the hibernation period, it was lower than predicted for lactating females. In addition, muscle-fiber number and cross-sectional area were unchanged in these muscles, suggesting only limited muscle atrophy. In support of these observations, there was a moderate but significant increase in the proportion of fast-twitch fibers only in the biceps femoris, with a concomitant decrease in citrate synthase activity, but no alteration of the fiber ratio in the gastrocnemius during hibernation. These findings suggest that hibernating bears, particularly lactating females, do use some protein, in concert with fat catabolism, as a metabolic substrate and as a source of water. However, the extent of this protein use is moderate and is associated with limited alteration of muscle structure, characteristic of disuse atrophy.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"414-24"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515429","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20596264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physiological effects of sublethal acid exposure in juvenile rainbow trout on a limited or unlimited ration during a simulated global warming scenario.","authors":"L M D'Cruz,&nbsp;J J Dockray,&nbsp;I J Morgan,&nbsp;C M Wood","doi":"10.1086/515421","DOIUrl":"https://doi.org/10.1086/515421","url":null,"abstract":"<p><p>Changes in the physiology and cost of living of fish were studied during exposure to simulated global warming and environmental acidification, alone and in combination. Trout were exposed to slightly elevated water temperatures (+2 degrees C), in the presence and absence of sublethal acidity (pH 5.2) in synthetic softwater for 90 d (8 degrees - 12 degrees C). Fish were either fed to satiation (ca. 1%-3% of their wet-body weight daily) or fed 1% of their wet-body weight once every 4 d. Satiation-fed fish exposed to sublethal pH showed no ionoregulatory disturbances but exhibited increased appetites and growth compared to fish in control pH waters. In contrast, fish maintained on a limited ration did not grow and showed typical ionoregulatory responses to acid stress, with lower whole-body Na+ and Cl- concentrations and greater mortality. Detrimental effects were greater in the global warming scenario (+2 degrees C). Overall, a slight temperature increase and sublethal pH increased the cost of living as determined by increased food consumption in satiation-fed fish and greater mortalities in fish maintained on a limited ration. Most important, these findings suggest that fish given sufficient food can compensate for increased energy expenditure or difficulties in maintaining ion balance associated with low pH exposure.</p>","PeriodicalId":79527,"journal":{"name":"Physiological zoology","volume":"71 4","pages":"359-76"},"PeriodicalIF":0.0,"publicationDate":"1998-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/515421","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20595751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}