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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 183 (1977), S. 41-59 
    ISSN: 1432-041X
    Keywords: Imaginal discs ; Pattern formation ; Cell death ; Duplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe the range of phenotypes caused by cell death when larvae of the heat-sensitive cell-lethal mutant,l(1)ts726 ofDrosophila, are subjected to heat treatment at different stages of development. When the treatment extends into the pupal period, certain bristles fail to develop but the disc derivatives are otherwise normal. Earlier treatments cause the replacement of sets of leg and eye-antennal markers by mirror image duplications of neighbouring sets. The results are compared in detail with those expected under a gradient model proposed earlier to account for the phenotype. It is found that although the results for the second leg are in excellent agreement with the predictions of the model, a more elaborate hypothesis is necessary to account for the eye-antennal disc data. Abnormal head patterns fall into several distinct categories, any one of which could be explained by postulating the existence of a gradient, if other categories did not also occur. The markers affected in each case belong to overlapping sets, and each category of pattern can be induced by heat treatments administered throughout the temperature-sensitive period. The statistical distribution of the data is such that only one category of pattern would be detected in a small scale experiment. The possible implications relative to pattern formation in normal development are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Adélie Penguin ; energetics ; Microclimate ; Reproduction ; Thermoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We measured meteorological conditions and estimated the energy costs of thermoregulation for young and adult Adélie Penguins (Pygoscelis adeliae) at a breeding colony near the Antarctic Peninsula. Air temperatures averaged 〈 5°C and strong winds were frequent. Operative temperatures (Te) for adults ranged from −8 to 28°C, averaging 5–6°C, for the period from courtship to fledging of chicks. The average energy cost of thermoregulation (Cth) for adult penguins was equivalent to 10–16% of basal metabolism. Cth comprised about 15% of the estimated daily energy budget (DEB) of incubating adults, but only about 1% of the DEB of adults feeding chicks. The Te's for chicks older than 14 days ranged from 0 to 31°C, averaging 8.0 C. The Cth for downy chicks ranged from about 31% of minimal metabolic rate (MMR) in 1 kg chicks to about 10% of MMR in 3 kg chicks. Between initial thermal independence (age 12–14 days) and the cessation of parental feeding (age 35–40 days), chicks use about 10–11% of assimilated energy for thermoregulation. Cth is equivalent to about 17% of the MMR of fledglings during their 2–3 week fast. We observed no indication of thermal stress (i.e., conditions in which birds cannot maintain stable Tb) in adults and no indication of cold stress in any age class. However, on clear, calm days when air temperature exceeds 7–10°C for several hours, downy chicks are vulnerable to lethal hyperthermia.
    Type of Medium: Electronic Resource
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