The thermoregulatory potential of Ovis horn cores

2000 ◽  
Vol 78 (8) ◽  
pp. 1419-1426 ◽  
Author(s):  
Manfred Hoefs
Keyword(s):  
Heat Dissipation ◽  
Environmental Gradients ◽  
Exchange Capacity ◽  
Ovis Canadensis ◽  
Evolutionary Trend ◽  
Simple Index ◽  
Cranial Measurements ◽  
Heat Conservation ◽  
Thinhorn Sheep ◽  
Northwestern North America

Cranial measurements were taken from 378 Ovis skulls (258 male, 120 female), covering most subspecies of wild sheep. Horn core length and circumference data were used to estimate the core surface. This highly vascularized plexus constitutes the radiating area. A simple index of heat-exchange capacity was calculated by dividing the combined surfaces of two horn cores by the mass of the animal. This index provided a standard by means of which different types of sheep could be compared, as well as allowing the detection of correlations with environmental gradients, which would point to a thermoregulatory role for horn cores. It can be assumed that, for sheep living in cold climates, heat conservation is important, while for those living in hot environments, enhanced heat dissipation would be advantageous. Our data confirm this hypothesis. The thinhorn sheep (Ovis dalli and Ovis nivicola) of subarctic and arctic northwestern North America and northern Siberia have the smallest horn cores, with indices of 6.9-7.3 cm2/kg, while desert-dwelling types have indices of more than twice these values. For instance, the desert subspecies of the American bighorns (Ovis canadensis nelsoni, Ovis canadensis mexicana, Ovis canadensis cremnobates) have indices ranging from 15.1 to 16.5 cm2/kg. Other sheep types have indices of intermediate sizes. It is our position that this evolutionary trend to vary core size in response to ambient temperature is independent of a parallel trend to increase horn size for the benefit of enhancing reproductive success.

Some aspects of Sphagnum ecology

1986 ◽  
Vol 64 (2) ◽  
pp. 416-426 ◽  
Author(s):  
Richard E. Andrus
Keyword(s):  
Desiccation Tolerance ◽  
Cation Exchange Capacity ◽  
Environmental Gradients ◽  
Exchange Capacity ◽  
Small Scale ◽  
Desiccation Resistance ◽  
Photosynthetic Response ◽  
Drying Rates ◽  
Water Holding ◽  
Water Contents

Sphagnum species are ecologically prominent wetland plants with xerophytic adaptations and succession-directing acidification capabilities. Species are organized along environmental gradients of pH, cation concentrations, hummock and hollow, wet versus dry, shade versus sun, coastal versus inland, and cold versus warm. The known factors responsible for this organization include cation-exchange capacity, desiccation tolerance, desiccation resistance, water-holding capacity, drying rates, and photosynthetic response at differing water contents. Small-scale distribution of Sphagnum species can be better explained for ombrotrophic sites than for minerotrophic sites.

Heat balance and reactivity to endotoxin

1963 ◽  
Vol 204 (4) ◽  
pp. 719-722 ◽  
Author(s):  
F. Robert Fekety
Keyword(s):  
Ambient Temperature ◽  
Heat Balance ◽  
Heat Dissipation ◽  
Body Temperatures ◽  
Endogenous Pyrogen ◽  
Heat Conservation

Shorn rabbits, supine restrained rabbits, and rabbits in the cold had relatively low body temperatures because their caloric losses were greater than normal, and they did not develop fever after endotoxin, adrenaline, or endogenous pyrogen. In such animals, mechanisms of heat conservation seemed maximally operative prior to testing; the absence of fever was related to limits imposed by ambient temperature upon heat conservation by further vasoconstriction in the ear, and shivering responses were not uniformly seen. Ordinarily appropriate late mechanisms of heat dissipation were noted after endotoxin despite the lack of fever. Febrile responses became possible when shorn animals were warmed. After repeated endotoxin injection, greater vasoconstriction over the trunk was feasible, the limitations of ambient temperature upon heat conservation became less decisive, and fever resulted. The unusual circulatory and thermal responses of chilled rabbits should be taken into consideration when performing similar experiments.

Skull ontogeny of the pronghorn (Antilocapra americana) in the comparative context of native North American ungulates

2020 ◽  
Vol 98 (3) ◽  
pp. 165-174 ◽  
Author(s):  
S.R. Moyano ◽  
M.M. Morales ◽  
N.P. Giannini
Keyword(s):  
Odocoileus Virginianus ◽  
North American ◽  
Feeding Habits ◽  
Ovis Canadensis ◽  
Bison Bison ◽  
Postnatal Ontogeny ◽  
Antilocapra Americana ◽  
Native North American ◽  
Cranial Measurements ◽  
Ontogenetic Trajectory

The pronghorn (Antilocapra americana (Ord, 1815)) is the single survivor of a largely extinct, isolated pecoran lineage (Antilocapridae) native to North America. We describe postnatal ontogeny of its skull in a comparative framework inclusive of representatives of other typical North American ungulate linages, all of which partially overlap in geographic distribution and share habitat with A. americana. To describe allometric growth, we took 23 linear cranial measurements in 30 specimens of A. americana and applied bi- and multi-variate statistics. The skull of A. americana generally grew with negative rates in width and height dimensions, and with positive rates in length, including an elongation of rostrum, particularly the nasals, and a relative narrowing of the braincase. We compared skull development in A. americana with development in two cervids (white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) and wapiti (Cervus canadensis Erxleben, 1777)) and two bovids (bighorn sheep (Ovis canadensis Shaw, 1804) and American bison (Bison bison (Linnaeus, 1758))). The multivariate ontogenetic trajectory of A. americana overlapped greatly with that of Odocoileus virginianus, and differed from the other species in varying degrees. These results indicated an essentially convergent pattern of skull growth with species showing important functional similarities, such as cervids of comparable size and feeding habits.

Geographic variation in body size of five Australian marsupials supports Bergmann’s thermoregulation hypothesis

2020 ◽  
Vol 101 (4) ◽  
pp. 1010-1020
Author(s):  
Alyson M Stobo-Wilson ◽  
Teigan Cremona ◽  
Brett P Murphy ◽  
Susan M Carthew
Keyword(s):  
Body Size ◽  
Ambient Temperature ◽  
Geographic Variation ◽  
Heat Dissipation ◽  
Geographic Range ◽  
Bergmann’S Rule ◽  
Maximum Temperature ◽  
Bergmann's Rule ◽  
Skull Length ◽  
Heat Conservation

Abstract Despite a large body of research, little agreement has been reached on the ultimate driver(s) of geographic variation in body size (mass and/or length). Here we use skull length measurements (as a surrogate for body mass) from five Australian marsupial species to test the primary hypotheses of geographic variation in body size (relating to ambient temperature, productivity, and seasonality). We used a revised articulation of Bergmann’s rule, wherein evidence for thermoregulation (heat dissipation or heat conservation) is considered supportive of Bergmann’s rule. We modeled the skull lengths of four Petaurid glider species and the common brushtail possum (Trichosurus vulpecula) as a function of indices of ambient temperature, productivity, and seasonality. The skull length of Petaurus ariel, P. notatus, and the squirrel glider (P. norfolcensis), increased with increasing winter minimum temperature, while that of T. vulpecula decreased with increasing summer maximum temperature. The skull length of P. ariel decreased with indices of productivity, falsifying the productivity hypothesis. Only P. ariel met the hypothesis of seasonality, as skull length increased with increasing seasonality. Thermoregulation was the most consistently supported driver of geographic variation in body size, as we found evidence of either heat conservation or heat dissipation in four of the five species examined. We found the geographic range of the individual species and the climate space in which the species occurred was integral to understanding the species’ responses to climate variables. Future studies should use specimens that are representative of a species’ entire geographic range, encompass a variety of climatic regions, and use consistent methodologies and terminology when testing drivers of geographic variation in body size.

Sex-specific responses of bud burst and early development to nongrowing season warming and drought in Populus cathayana

2018 ◽  
Vol 48 (1) ◽  
pp. 68-76 ◽  
Author(s):  
Lei Yu ◽  
Yan Han ◽  
Yonglei Jiang ◽  
Tingfa Dong ◽  
Yanbao Lei
Keyword(s):  
Elevated Temperature ◽  
Gas Exchange ◽  
Environmental Gradients ◽  
Field Capacity ◽  
Exchange Capacity ◽  
Life History Strategies ◽  
Bud Burst ◽  
Populus Cathayana ◽  
Species Specific ◽  
Open Question

Bud burst is one of the most observable phenological stages in tree species, and its responses to environmental factors are found to be species-specific. Nevertheless, for dioecious plants, whether the bud burst responses are sex specific remains an open question, as do the underlying physiological mechanisms. Here, we investigated the effect of elevated temperature (+2 °C) and drought (30% field capacity) during December–March on bud development, gas exchange, water and nitrogen status, and carbohydrate metabolism in female and male Populus cathayana to understand how nongrowing season warming and drought modifies physiological and phenological traits. Our results showed that at ambient temperature, males experienced earlier bud burst than females. Winter warming significantly delayed bud burst and even synchronized it for both sexes because of the greater responsiveness of males. Although drought exerted little effect on the timing of bud burst, it significantly reduced bud fresh mass and limited bud growth by decreasing gas exchange capacity and nonstructural carbohydrate (NSC) accumulation; moreover, females were more affected by drought stress. The significant sex × watering × temperature interactions for δ13C and NSC indicate that sexual dimorphism in these condition-specific traits would increase along the environmental gradients, implying contrasting life history strategies in different ecological scenarios. The convergence in the time for bud burst caused by elevated temperature might exaggerate the competition among males, thus influencing the sex ratio, structure, and functioning of P. cathayana populations.

scholarly journals A temperate endotherm trades thermoregulation for self-preservation: stress-induced changes in surface temperature as thermoregulatory trade-offs

2020 ◽  
Author(s):  
Joshua Kenneth Robertson ◽  
Gabriela F Mastromonaco ◽  
Gary Burness
Keyword(s):  
Surface Temperature ◽  
Heat Dissipation ◽  
Stress Exposure ◽  
Ambient Temperatures ◽  
Resource Limited ◽  
Trade Offs ◽  
Heat Conservation ◽  
Induced Changes ◽  
And Control ◽  
Energetic Expenditure

Coping with stressors can require substantial energetic investment, and when resources are limited, such investment can preclude simultaneous expenditure on other biological processes. Among endotherms, energetic demands of thermoregulation can be immense, yet whether a stress response is sufficient to induce changes in thermoregulatory investment appears unexplored. We tested the hypothesis that stress-induced changes in surface temperature, a well-documented phenomenon across vertebrates, stem from a trade-off between thermoregulation and stress responsiveness, whereby individuals seek to reduce energetic expenditure on thermoregulation in challenging environments (the "Thermoprotective Hypothesis"). We predicted that surface temperature and dry heat loss of individuals that are resource-limited would fall under stress exposure at low ambient temperatures and rise under stress exposure at high ambient temperatures when compared with non-resource limited individuals. To test our predictions, we exposed Black-capped Chickadees to rotating stressors and control treatments (ndays/treatment = 30; paired treatments) across an ambient temperature gradient whilst remotely monitoring both feeding behaviour and surface temperature. Supporting the Thermoprotective Hypothesis, our results showed that: 1) social subordinates (n = 12), who fed less than social dominants and alone suffered stress-induced declines in mass, displayed significantly larger changes in surface temperature following stress exposure than social dominants (n = 8), and 2) stress-induced changes in surface temperature significantly increased heat conservation at low ambient temperatures, and heat dissipation at high ambient temperatures among social subordinates alone. These results suggest that Black-capped Chickadees adjust their thermoregulatory strategies under stress when resources are limited and support the hypothesis that stress-induced changes in temperature are functionally significant.

scholarly journals Social hierarchy reveals thermoregulatory trade-offs in response to repeated stressors

2020 ◽  
Vol 223 (21) ◽  
pp. jeb229047
Author(s):  
Joshua K. Robertson ◽  
Gabriela F. Mastromonaco ◽  
Gary Burness
Keyword(s):  
Heat Dissipation ◽  
Stress Exposure ◽  
Ambient Temperatures ◽  
Trade Offs ◽  
Stress Responsiveness ◽  
Heat Conservation ◽  
Social Subordination ◽  
Induced Changes ◽  
And Control ◽  
Energetic Expenditure

ABSTRACTCoping with stressors can require substantial energetic investment, and when resources are limited, such investment can preclude simultaneous expenditure on other biological processes. Among endotherms, energetic demands of thermoregulation can also be immense, yet our understanding of whether a stress response is sufficient to induce changes in thermoregulatory investment is limited. Using the black-capped chickadee as a model species, we tested a hypothesis that stress-induced changes in surface temperature (Ts), a well-documented phenomenon across vertebrates, stem from trade-offs between thermoregulation and stress responsiveness. Because social subordination is known to constrain access to resources in this species, we predicted that Ts and dry heat loss of social subordinates, but not social dominants, would fall under stress exposure at low ambient temperatures (Ta), and rise under stress exposure at high Ta, thus permitting a reduction in total energetic expenditure toward thermoregulation. To test our predictions, we exposed four social groups of chickadees to repeated stressors and control conditions across a Ta gradient (n=30 days/treatment/group), whilst remotely monitoring social interactions and Ts. Supporting our hypothesis, we show that: (1) social subordinates (n=12), who fed less than social dominants and alone experienced stress-induced mass-loss, displayed significantly larger changes in Ts following stress exposure than social dominants (n=8), and (2) stress-induced changes in Ts significantly increased heat conservation at low Ta and heat dissipation at high Ta among social subordinates alone. These results suggest that chickadees adjust their thermoregulatory strategies during stress exposure when resources are limited by ecologically relevant processes.

TEM observation of iron oxide pillars in montmorillonite

1990 ◽  
Vol 48 (4) ◽  
pp. 882-883
Author(s):  
H. Mori ◽  
Y. Murata ◽  
H. Yoneyama ◽  
H. Fujita
Keyword(s):  
Aqueous Solution ◽  
Iron Oxide ◽  
Fine Particles ◽  
Aqueous Suspension ◽  
Volume Ratio ◽  
Exchange Capacity ◽  
Nano Composites ◽  
Pillared Montmorillonite ◽  
Topographic Features ◽  
Transmission Electron

Recently, a new sort of nano-composites has been prepared by incorporating such fine particles as metal oxide microcrystallites and organic polymers into the interlayer space of montmorillonite. Owing to their extremely large specific surface area, the nano-composites are finding wide application[1∼3]. However, the topographic features of the microstructures have not been elucidated as yet In the present work, the microstructures of iron oxide-pillared montmorillonite have been investigated by high-resolution transmission electron microscopy.Iron oxide-pillared montmorillonite was prepared through the procedure essentially the same as that reported by Yamanaka et al. Firstly, 0.125 M aqueous solution of trinuclear acetato-hydroxo iron(III) nitrate, [Fe3(OCOCH3)7 OH.2H2O]NO3, was prepared and then the solution was mixed with an aqueous suspension of 1 wt% clay by continuously stirring at 308 K. The final volume ratio of the latter aqueous solution to the former was 0.4. The clay used was sodium montmorillonite (Kunimine Industrial Co.), having a cation exchange capacity of 100 mequiv/100g. The montmorillonite in the mixed suspension was then centrifuged, followed by washing with deionized water. The washed samples were spread on glass plates, air dried, and then annealed at 673 K for 72 ks in air. The resultant film products were approximately 20 μm in thickness and brown in color.

Sign in / Sign up

Export Citation Format

Share Document