Author Keywords: Thermoregulation; heat transfer; nestlings; huddling; Zonotrichia leucophyrs; bird 相似文献
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1. 1.|To determine the thermoregulatory prowess of altricial nestlings, we conducted both equilibrium and transient analyses of white-crowned sparrow nestings, a representative fringillid.
2. 2.|For an individual nestling at thermal equilibrium, feather development is the major factor reducing heat loss after 2 days of age; tissue- and boundary-layer resistances are of minor importance.
3. 3.|The nest substantially reduces wind speeds near the nestlings. Heat transfer through the nest material is of only moderate importance. Evaporation also appears to be a small proportion of total heat loss during hypothermia in natural environments.
4. 4.|Net long-wave radiant exchange is also minor, but short-wave radiation is potentially a major component of the nestling's energy budget, approaching the magnitude of maximal metabolic heat production.
5. 5.|When nestlings cool, their body mass and metabolic rate are also major importance in determining the rate of cooling, and (for metabolism) the equilibrium temperature as well.
6. 6.|The huddling together of nestlings is perhaps the single most important factor affecting heat transfer.
7. 7.|An older brood actually has more insulation than does an adult in the same microclimate.
1. 1.|Critical thermal maxima (CTMax) and minima (CTMin) were measured to evalute thermal hardening in Rana catesbeiana.
2. 2.|Tadpoles show heat hardening and CTMax acclimation, and both responses are influenced by developmental stage.
3. 3.|The first evidence of cold hardening in vertebrates is reported here.
4. 4.|Heat hardening significantly reduces cold tolerance, but there is otherwise no evidence of a cross-hardening effect.
Author Keywords: Thermal acclimation; thermal hardening; hardening; heat hardening; cold hardening; critical thermal maxima; critical thermal minima; developmental stage; metamorphosis; tadpoles; Rana catesbeiana 相似文献
1. 1.|The effect of thyroidectomy at 12 days of age on weight gain, and on heat production and thermoregulatory ability of 4- to 5-week-old chickens at temperatures within and below the thermo-neutral zone was investigated.
2. 2.|Despit the absence of thyroid tissue, as demonstrated with radioiodine, a small amount of thyroxine was found in the plasma of some thyroidectomized (TX) birds.
3. 3.|Thyroidectomy depressed weight gain; pair-fed controls grew significantly faster than TX birds.
4. 4.|Resting heat production of TX birds at thermoneutrality (30°C) was depressed by 18% (P < 0.001) and body temperature by 0.4°C (P < 0.001).
5. 5.|At 12°C heat production of TX birds was similar to that of controls but the body temperature of TX birds was 0.7°C lower (P < 0.001).
6. 6.|Thyroidectomized birds were unable to regulate body temperature at 5°C even if thyroxine was provided on the day before and at the time of cold-exposure. This inability to thermoregulate was probably due to inadequate insulation and poor nutritional status.
Author Keywords: Gallus domesticus; thyroidectomy; thyroxine; heat production; thermoregulation; body temperature 相似文献