Physiological and Biochemical Zoology最新文献

{"title":"Nestling Altricial Rodents and Lagomorphs Are Not Ectotherms.","authors":"Richard W Hill","doi":"10.1086/721446","DOIUrl":"https://doi.org/10.1086/721446","url":null,"abstract":"<p><p>AbstractBased on the synthesis of data on metabolic rates of 15 species investigated at moderate ambient temperatures, nestlings of most studied species of altricial rodents and lagomorphs exhibit thermoregulatory control of thermogenesis within 3 d after birth, signifying that they express physiological thermoregulation for 86%-100% of their time as nestlings. Classifying nestlings as ectotherms (or poikilotherms) is thus inappropriate and fosters misconceptions regarding their body temperatures (<i>T</i>_b's), control of <i>T</i>_b-sensitive functions (e.g., cardiac output), and energetics of development. The fact that nestlings live as litters in nests means that their thermoregulatory capacities in their actual, natural lives often far exceed the capacities they exhibit as isolated individuals-pointing to a pressing need for improved understanding of the physiology of litters. Litters in nests are already known in two cases to exhibit true homeothermy at ages when individuals studied in isolation express only modest thermoregulatory abilities. Golden (Syrian) hamster nestlings are exceptional, requiring 2 wk to develop thermoregulatory thermogenesis. They are properly considered ectotherms at up to 2 wk of age, helping to clarify that most species-being dramatically different-are not.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33464605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variation in Melanin Content of Lizard Livers: Hybrids Turning to the Dark Side.","authors":"Victoria Del Gaizo Moore,&nbsp;Gregory J Haenel","doi":"10.1086/721445","DOIUrl":"https://doi.org/10.1086/721445","url":null,"abstract":"<p><p>AbstractPigments such as melanin are most often associated with the surface of an organism, providing functions such as coloration and protection from UV radiation. However, the internal organs of some species also contain melanin. Internal melanin may also perform protective functions when cellular stress is experienced. We tested liver tissue of two tree lizard species that experienced introgression of their mitochondria to see whether melanin was present and whether it was at higher concentrations in the types of lizards thought to be under cellular stress. Previous work found that mitochondria from livers of hybrid tree lizards (those with introgressed mitochondrial DNA) had higher levels of ATP production at higher temperatures than both parental species and showed indications of dysfunction. Therefore, we predicted that if internal melanin functions to mediate the impact of damaging by-products of metabolism, such as excessive reactive oxygen species (ROS), melanin would be highest in livers of lizards with introgressed mitochondria. To test this, we used a melanin-specific stain on liver tissue sections and measured melanin concentration with spectrophotometry of heavy-membrane fractions from whole-liver homogenates of both parental species and their hybrids with introgressed mitochondria. Slides of liver sections treated with a melanin-specific stain revealed that hybrids contained melanin and had significantly higher levels of it than either parental species. Spectrophotometry gave the same result. This distribution of internal melanin matches the pattern expected if melanin functions as a compensatory mechanism to deal with higher ATP production and the subsequent high levels of ROS expected in these hybrid lizards. Future studies will examine this mechanistically.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40387201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variation of Rodents' Body Temperature across Elevation in Alps.","authors":"Ilaria Melcore,&nbsp;Sandro Bertolino,&nbsp;Zbyszek Boratyński","doi":"10.1086/721477","DOIUrl":"https://doi.org/10.1086/721477","url":null,"abstract":"<p><p>AbstractUnderstanding the physiological adaptations of animals living in mountain landscapes is a key to predicting the responses of individuals to environmental changes, especially those imposed by climate. In this regard, the mechanism of body temperature regulation is particularly important in determining the physiological limits for activity under hypoxic and climatic stressful conditions. Numerous studies have shown that body temperature of rodents and other animals decreases with elevation and with extreme winter temperatures. But surprisingly, it is still not known how body temperature of wild animals varies along elevation during their reproductive seasons. We studied variation in core body temperature among individuals (<math><mrow><mi>N</mi><mo>=</mo><mn>294</mn></mrow></math>) of four rodent species (<i>Apodemus flavicollis</i>, <i>Apodemus sylvaticus</i>, <i>Apodemus alpicola</i>, <i>Myodes glareolus</i>) and its association with elevation (from 400 to 1,822 m asl), accounting for variation in environment temperature, microhabitat structure, body condition, and sex. Results showed a strong positive effect of elevation and a more limited effect of environmental temperature on rodents' body temperature during spring and summer. The effect of elevation on body temperature was influenced neither by interactions with environmental temperature or sex nor by the microhabitat structure. We suggest that in normothermic condition at high elevations, small mammals experiencing hypoxic exposure might show physiological adjustments for increasing efficiency of thermoregulation in low oxygen conditions.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40380291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PUFA Changes in White Adipose Tissue during Hibernation in Common Hamsters.","authors":"Carina Siutz,&nbsp;Matthias Nemeth,&nbsp;Ruth Quint,&nbsp;Karl-Heinz Wagner,&nbsp;Eva Millesi","doi":"10.1086/721444","DOIUrl":"https://doi.org/10.1086/721444","url":null,"abstract":"<p><p>AbstractHibernators save energy during winter by expressing torpor bouts characterized by strongly reduced body temperature and metabolic rate. Polyunsaturated fatty acids (PUFAs), specifically n-6 PUFAs, are known to positively affect hibernation performance and thereby energy savings predominantly in fat-storing hibernators. Accordingly, hibernators usually retain PUFAs and mobilize monounsaturated fatty acids (MUFAs) or saturated fatty acids (SFAs) during hibernation. In food-storing common hamsters (<i>Cricetus cricetus</i>), however, we previously found that PUFA proportions in white adipose tissue (WAT) decreased during winter, indicating that individuals did mobilize PUFAs. To further investigate these patterns, we analyzed PUFA changes in WAT during hibernation as well as hibernation performance in free-ranging and captive common hamsters with lower prehibernation PUFA proportions compared to those in the previous study. Under controlled conditions, total PUFAs, n-6 PUFAs, and SFAs increased while n-3 PUFAs and MUFAs decreased during hibernation. Higher prehibernation n-6 PUFA proportions resulted in fewer torpor bouts and less time spent in torpor. In free-ranging hamsters, n-6 PUFAs increased while n-3 PUFAs and SFAs decreased during winter. Prehibernation n-6 PUFA proportions, however, did not affect hibernation performance. In summary, these results indicate that the mobilization or retention of n-6 PUFAs during hibernation could depend on their availability in WAT or in the diet before the onset of the hibernation period.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40386644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Altricial Bird Early-Stage Embryos Express the Molecular \"Machinery\" to Respond to and Modulate Maternal Thyroid Hormone Cues.","authors":"Suvi Ruuskanen,&nbsp;Mikaela Hukkanen,&nbsp;Natacha Garcin,&nbsp;Nina Cossin-Sevrin,&nbsp;Bin-Yan Hsu,&nbsp;Antoine Stier","doi":"10.1086/721556","DOIUrl":"https://doi.org/10.1086/721556","url":null,"abstract":"<p><p>AbstractMaternal hormones, such as thyroid hormones (THs) transferred to embryos and eggs, are key signaling pathways for mediating maternal effects. To be able to respond to maternal cues, embryos must express the key molecular \"machinery\" of hormone pathways, such as enzymes and receptors. While altricial birds begin TH production only at or after hatching, experimental evidence suggests that their phenotype can be influenced by maternal THs deposited into the egg. However, it is not understood how or when altricial birds express genes in the TH pathway. For the first time, we measured the expression of key TH-pathway genes in altricial embryos by using two common altricial ecological model species, pied flycatcher (<i>Ficedula hypoleuca</i>) and blue tit (<i>Cyanistes caeruleus</i>). Deiodinase <i>DIO1</i> gene expression could not be reliably confirmed in either species, but deiodinase enzyme genes <i>DIO2</i> and <i>DIO3</i> were expressed in both species. Given that <i>DIO2</i> converts thyroxine to biologically active triiodothyronine and that <i>DIO3</i> mostly converts triiodothyronine to inactive forms of THs, our results suggest that embryos may modulate maternal signals. TH receptors (<i>THRA</i> and <i>THRB</i>) and a monocarboxylate membrane transporter gene (<i>SLC16A2</i>) were also expressed, enabling TH responses. Our results suggest that altricial embryos may be able to respond to and potentially modulate maternal signals conveyed by THs in early development.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33510702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corticosterone Alters Body Weight, but Not Metabolites, during Chronic Stress.","authors":"Carolyn M Bauer,&nbsp;Michelle A Oranges,&nbsp;Gaylinn Firempong,&nbsp;L Michael Romero","doi":"10.1086/721297","DOIUrl":"https://doi.org/10.1086/721297","url":null,"abstract":"<p><p>AbstractThe stress response is partially mediated by increased levels of circulating glucocorticoids. While the stress response may be adaptive in the short term, chronically elevated levels of glucocorticoids can be pathological. We aimed to verify that chronic stress causes metabolic dysregulation via increased corticosterone (Cort) exposure by monitoring free fatty acid (FFA) concentrations (evidence of fat breakdown), uric acid concentrations (evidence of protein breakdown), and organ weights (furcular fat, abdominal fat, liver, and pectoralis muscle) in chronically stressed juvenile house sparrows (<i>Passer domesticus</i>). The sparrows were chronically stressed for 3 wk by applying a series of rotating mild psychological stressors. One group of birds received injections of a glucocorticoid steroidogenesis inhibitor (mitotane) and a second group received injections of a glucocorticoid receptor antagonist (RU486) halfway through the chronic stress period to test whether glucocorticoids are responsible for protein and fat catabolism during chronic stress. Toward the end of the chronic stress period, mitotane birds increased weight compared to control and RU486 birds. Contrary to expectations, we saw no differences in FFA or uric acid levels between control and mitotane birds, but RU486 temporarily decreased stress-induced uric acid levels. Neither mitotane nor RU486 significantly altered organ weights at the end of the 3 wk. In conclusion, Cort does appear to negatively affect body weight, but the mechanism does not appear to involve increased protein or lipid metabolism.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40422757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Within-Generation and Transgenerational Plasticity of a Temperate Salmonid in Response to Thermal Acclimation and Acute Temperature Stress.","authors":"Chantelle M Penney,&nbsp;Joshua K R Tabh,&nbsp;Chris C Wilson,&nbsp;Gary Burness","doi":"10.1086/721478","DOIUrl":"https://doi.org/10.1086/721478","url":null,"abstract":"<p><p>AbstractThe rise in temperature associated with climate change may threaten the persistence of stenothermal organisms with limited capacities for beneficial thermal acclimation. We investigated the capacity for within-generation and transgenerational thermal responses in brook trout (<i>Salvelinus fontinalis</i>), a cold-adapted salmonid. Adult fish were acclimated to temperatures within (10°C) and above (21°C) their thermal optimum for 6 mo before spawning, then mated in a full factorial breeding design to produce offspring from cold- and warm-acclimated parents and bidirectional crosses between parents from both temperature treatments. Offspring from families were subdivided and reared at two acclimation temperatures representing their current (15°C) and anticipated future (19°C) habitat temperatures. Offspring thermal physiology was measured as the rate of oxygen consumption (Mo₂) during an acute change in temperature (increase of 2°C h^-1) to observe their Mo₂-temperature relationship. We recorded resting Mo₂, peak (highest achieved, thermally induced) Mo₂, and critical thermal maximum (CTM) as performance metrics. Although limited, within-generation plasticity was greater than transgenerational plasticity, with offspring warm acclimation elevating CTM by 0.5°C but slightly lowering peak thermally induced Mo₂. Transgenerational plasticity was evident as a slightly elevated resting Mo₂ and a shift of the Mo₂-temperature relationship to higher rates overall in offspring from warm-acclimated parents. Furthermore, offspring whose parents were warm acclimated were in worse condition than those whose parents were cold acclimated. Both parents contributed to offspring thermal responses; however, the paternal effect was stronger. Despite the existence of within-generation and transgenerational plasticity in brook trout, it is unlikely that these will be sufficient for coping with long-term changes to environmental temperatures.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33481818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cascading Effects of Conspecific Aggression on Oxidative Status and Telomere Length in Zebra Finches.","authors":"Martin Quque,&nbsp;Charly Ferreira,&nbsp;Sebastian Sosa,&nbsp;Quentin Schull,&nbsp;Sandrine Zahn,&nbsp;François Criscuolo,&nbsp;Josefa Bleu,&nbsp;Vincent A Viblanc","doi":"10.1086/721252","DOIUrl":"https://doi.org/10.1086/721252","url":null,"abstract":"<p><p>Living in social groups may exacerbate interindividual competition for territory, food, and mates, leading to stress and possible health consequences. Unfavorable social contexts have been shown to elevate glucocorticoid levels (often used as biomarkers of individual stress), but the downstream consequences of socially stressful environments are rarely explored. Our study experimentally tests the mechanistic links between social aggression, oxidative stress, and somatic maintenance in captive zebra finches (<i>Taeniopygia guttata</i>). Over 64 d, we measured the effects of aggression (received or emitted) on the individual oxidative status, body condition, and changes in relative telomere length (rTL) of birds living in high- and low-social-density conditions. Using path analyses, we found that birds living at high social density increased their aggressive behavior. Birds receiving the highest number of aggressions exhibited the strongest activation of antioxidant defenses and highest plasmatic levels of reactive oxygen metabolites. In turn, this prevented birds from maintaining or restoring telomere length between the beginning and the end of the experiment. Received aggression also had a direct negative effect on changes in rTL, unrelated to oxidative stress. In contrast, emitted aggression had no significant effect on individual oxidative stress or changes in rTL. Body condition did not appear to affect the physiological response to aggression or oxidative stress. At low density, we found trends that were similar to those at high density but nonsignificant. Our study sheds light on the causal chain linking the social environment and aggressive behavior to individual oxidative stress and telomere length. The long-term consequences of socially induced stress on fitness remain to be characterized.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40678725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Differential Changes in Circulating Steroid Hormones in Hibernating Brown Bears: Preliminary Conclusions and Caveats.","authors":"Anne Mette Frøbert,&nbsp;Julia N C Toews,&nbsp;Claus G Nielsen,&nbsp;Malene Brohus,&nbsp;Jonas Kindberg,&nbsp;Niels Jessen,&nbsp;Ole Fröbert,&nbsp;Geoffrey L Hammond,&nbsp;Michael T Overgaard","doi":"10.1086/721154","DOIUrl":"https://doi.org/10.1086/721154","url":null,"abstract":"<p><p>Brown bears are obese when they enter the den, and after 6 mo of hibernation and physical inactivity, bears show none of the adverse consequences of a sedentary lifestyle in humans, such as cardiovascular disease, type 2 diabetes, and kidney failure. The metabolic mechanisms that drive hibernation physiology in bears are poorly defined, but systemic endocrine regulators are likely involved. To investigate the potential role of steroid hormones, we quantified the total levels of 12 steroid hormones, the precursor cholesterol, sex hormone-binding globulin (SHBG), and corticosterone-binding globulin (CBG) in paired serum samples from subadult free-ranging Scandinavian brown bears during the active and hibernation states. During hibernation, androstenedione and testosterone were significantly decreased in subadult female bears (<math><mrow><mi>n</mi><mo>=</mo><mn>13</mn></mrow></math>), whereas they increased in all males but one (<math><mrow><mi>n</mi><mo>=</mo><mn>6</mn></mrow></math>) and therefore did not reach a significant difference. Despite this difference, SHBG increased more than 20-fold during hibernation for all bears. Compared with SHBG concentrations in humans, bear levels were very low in the active state, but during hibernation, levels equaled high levels in humans. The increased SHBG levels likely maintain a state of relative quiescence of the reproductive hormones in hibernating bears. Interestingly, the combination of SHBG and testosterone levels results in similar free bioavailable testosterone levels of 70-80 pM in both subadult and adult sexually active male bears, suggesting a role for SHBG in controlling androgen action during hibernation in males. Dehydroepiandrosterone sulfate, dihydrotestosterone, and estradiol levels were below the detection limit in all but one animal. The metabolically active glucocorticoids were significantly higher in both sexes during hibernation, whereas the inactive metabolite cortisone was reduced and CBG was low approaching the detection limit. A potential caveat is that the glucocorticoid levels might be affected by the ketamine applied in the anesthetic mixture for hibernating bears. However, increased hibernating cortisol levels have consistently been reported in both black bears and brown bears. Thus, we suggest that high glucocorticoid activity may support the hibernation state, likely serving to promote lipolysis and gluconeogenesis while limiting tissue glucose uptake to maintain a continuous glucose supply to the brain.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10416977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dive Performance and Aquatic Thermoregulation of the World's Smallest Mammalian Diver, the American Water Shrew (<i>Sorex palustris</i>).","authors":"Roman W Gusztak,&nbsp;Robert A MacArthur,&nbsp;Kevin L Campbell","doi":"10.1086/721186","DOIUrl":"https://doi.org/10.1086/721186","url":null,"abstract":"<p><p>Allometry predicts that the 12-17-g American water shrew (<i>Sorex palustris</i>)-the world's smallest mammalian diver-will have the highest diving metabolic rate coupled with the lowest total body oxygen storage capacity, skeletal muscle buffering capacity, and glycolytic potential of any endothermic diver. Consistent with expectations, and potentially owing to their low thermal inertia, water shrews had a significantly higher diving metabolic rate in 10°C water (8.77 mL O₂ g^-1 h^-1) compared with 30°C water (6.57 mL O₂ g^-1 h^-1). Unlike larger-bodied divers, muscle myoglobin contributed minimally (7.7%-12.4%) to total onboard O₂ stores of juvenile and adult water shrews, respectively, but was offset by high blood O₂ carrying capacities (26.4%-26.9% v/v). Diving was predominantly aerobic, as only 1.2%-2.3% of dives in 10°C and 30°C water, respectively, exceeded the calculated aerobic dive limits at these temperatures (10.8-14.4 s). The mean voluntary dive time of water shrews during 20-min trials in 3°C-30°C water was <math><mrow><mn>5.0</mn><mo>±</mo><mn>0.1</mn></mrow></math> s (<math><mrow><mi>N</mi><mo>=</mo><mn>25</mn></mrow></math>, <math><mrow><mi>n</mi><mo>=</mo><mn>1,628</mn></mrow></math>), with a mean maximum dive time of <math><mrow><mn>10.1</mn><mo>±</mo><mn>0.4</mn></mrow></math> s. However, the average dive duration (<math><mrow><mn>6.9</mn><mo>±</mo><mn>0.2</mn></mrow></math> s, <math><mrow><mi>n</mi><mo>=</mo><mn>257</mn></mrow></math>) of radio-telemetered shrews exclusively foraging in a simulated riparian environment (3°C water) for 12-28 h suggests that mean (but not maximum) dive times of water shrews in the wild may be longer. Mean dive duration, duration of the longest dive, and total time in water all decreased significantly as water temperature declined, suggesting that shrews employed behavioral thermoregulation to defend against immersion hypothermia. Additionally, free-diving shrews in the 24-h trials consistently elevated core body temperature by ∼1°C immediately before initiating aquatic foraging bouts and ended these bouts when body temperature was still at or above normal resting levels (∼37.8°C). We suggest that this observed predive hyperthermia aids to heighten the impressive somatosensory physiology, and hence foraging efficiency, of this diminutive predator while submerged.</p>","PeriodicalId":54609,"journal":{"name":"Physiological and Biochemical Zoology","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40599900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}