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  • 1
    Electronic Resource
    Electronic Resource
    Wind-induced ventilation of the burrow of the prairie-dog,Cynomys ludovicianus (1973)
    Springer
    Journal of comparative physiology 85 (1973), S. 1-14 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Where a fluid flows across a surface, such as wind over the earth, the velocity gradient created provides a potential source of work. This gradient might be employed by one burrowing animal to induce air-flow in its long, narrow burrow. The burrow of the black-tailed prairie-dog constitutes a respiratory dead-space of extraordinary magnitude in which diffusion appears inadequate for gas exchange. But the burrow is arranged in a manner appropriate for wind-induced ventilation, typically with two openings at opposite ends and with mounds surrounding these openings of two forms (Fig. 3), with one form on each end. When a breeze crosses the mounds, air enters the burrow through the lower mound and leaves through the higher. The same unidirectional flow is evident with scale models of real mounds on a model burrow in a wind tunnel; flow inside the burrow is nearly a linear function of flow across the mounds (Fig. 4). Wind-induced ventilation in the model burrow could also be induced with model mounds differing in shape but not height. Mounds with sharp rims were more effective exits for air than mounds with rounded tops; in nature such shape differences complement the differences in height.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694136
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  • 2
    Electronic Resource
    Electronic Resource
    Ventilatory responses of the burrowing Owl and Bobwhite to hypercarbia and hypoxia (1983)
    Springer
    Journal of comparative physiology 149 (1983), S. 527-533 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fractional concentration of CO2 within the occupied burrows of burrow-dwelling birds has been measured at 0.065 or higher while the fractional concentration of O2 can be 0.14 or lower. The ventilatory responses of the Burrowing Owl (Athene cunicularia) and a non-burrowing bird, the Bobwhite (Colinus virginianus), to the levels of hypercarbia, hypoxia and hypoxic hypercarbia likely encountered by this owl within its burrow were assessed. Ventilatory responses toFi CO 2 of 0.01, 0.03, 0.05 and 0.07 at normoxia; toFi CO 2 of 0.19, 0.17, 0.15 and 0.13 at normocarbia; and to combinedFi CO 2 andFi O 2 of 0.01:0.19, 0.03:0.17, 0.05:0.15 and 0.07:0.13 were measured by volumetric plethysmography. The Burrowing Owl exhibited a significantly attenuated ventilatory response to these levels of hypercarbia, hypoxia and hypoxic hypercarbia compared to the non-burrow-dwelling Bobwhite. A reduced ventilatory response to the hypoxic and hypercarbic stimuli has been previously observed in fossorial mammals, and is reported here for the first time in a burrow-dwelling bird. This reduced response is believed to represent an adaptation to burrow atmospheric conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690012
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Brain temperatures in birds (1976)
    Springer
    Journal of comparative physiology 110 (1976), S. 209-215 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Brain (hypothalamic) and cloacal temperatures were measured in heat-stressed Lesser Nighthawks (Chordeiles acutipennis), Mallards (Anas platyrhynchos), Pigeons (Columba livia), and White-Necked Ravens (Corvus cryptoleucus) and in one Roadrunner (Geococcyx californianus). Range of mean body masses was 0.047 to 1.156 kg. 2. In all these species brain temperatures were always below cloacal temperatures (Fig. 1). The body-to-brain temperature difference was maintained nearly constant within a species over a wide range of cloacal and air temperatures, and varied in magnitude from 0.80°C in the Roadrunner to 1.29°C in Mallards. 3. The presence of arete mirabile ophthalmicum was demonstrated in all five species. This rete may be associated with the observed pattern of brain temperature control. 4. The body-to-brain temperature difference may be important in avoiding brain damage during core hyperthermia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689309
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  • 4
    Electronic Resource
    Electronic Resource
    Brain temperature in the calliope hummingbird (Stellula calliope): a species lacking arete mirabile ophthalmicum (1987)
    Springer
    Journal of comparative physiology 157 (1987), S. 583-588 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Hypothalamic and colonic temperature were simultaneously measured in the calliope hummingbird (Stellula calliope). The vascular anatomy of the temporal region of these birds was also examined. 2. At air temperatures below 36°C, calliope hummingbirds regulated their body temperature between 35.6 and 40.6°C. At higher air temperatures, colonic temperature increased. 3. Brain temperature was lower than body temperature at high colonic temperatures (〉39.5°C). The body-to-brain temperature difference in birds with high body temperatures averaged 0.73°C and remained relatively constant at all colonic temperatures above 39.5°C. 4. At body temperatures below 39.5°C, brain temperature of calliope hummingbirds exceeded colonic temperature by an average of 1.38°C. The possible explanations for this observation are discussed. 5. Calliope hummingbirds lack arete mirabile ophthalmicum, the countercurrent arterial-venous heat exchanger responsible for brain cooling in other birds. 6. Brain cooling in calliope hummingbirds apparently depends on heat exchange between arterial blood flowing to the brain, and cool venous blood returning from evaporative and convective surfaces at sites other than therete mirabile ophthalmicum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00700978
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  • 5
    Electronic Resource
    Electronic Resource
    Role of theRete mirabile ophthalmicum in maintaining the body-to-brain temperature difference in pigeons (1979)
    Springer
    Journal of comparative physiology 129 (1979), S. 119-122 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Brain (hypothalamic) and colonic temperatures were measured in twenty adult pigeons (Columba livia) whose mean body mass was 0.377 kg. 2. In contrals, in sham operated birds, and in those pigeons in which one or both external ophthalmic arteries were occluded brain temperatures were always about 1°C (0.94 to 1.03) below body temperature (Fig. 2) over a range of air temperatures. 3. In pigeons in which arterial flow to theretia was totally blocked, the normal pattern of body-to-brain temperature difference wasreversed, such that brain temperature was always higher than body temperature by a mean of 0.36 °C (Fig. 2, Table 1). 4. Therete mirabile ophthalmicum of pigeons plays a central role in the maintenance of the body-to-brain temperature difference which may be important in avoiding brain damage during core hyperthermia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798175
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    Paper (German National Licenses)
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