科研之友
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摘要
Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or environmental demands, thereby influencing fitness. Summit metabolic rate (M-sum = maximal thermogenic capacity) is one such flexible trait. Skeletal muscle and heart masses and myocyte metabolic intensity are potential drivers of M-sum flexibility in birds. We examined correlations of skeletal muscle and heart masses and pectoralis muscle citrate synthase (CS) activity (an indicator of cellular metabolic intensity) with M-sum in house sparrows (Passer domesticus) and dark-eyed juncos (Junco hyemalis) to determine whether these traits are associated with M-sum variation. Pectoralis mass was positively correlated with M-sum for both species, but no significant correlation remained for either species after accounting for body mass (M-b) variation. Combined flight and leg muscle masses were also not significantly correlated with M-sum for either species. In contrast, heart mass was significantly positively correlated with M-sum for juncos and nearly so (P = 0.054) for sparrows. Mass-specific and total pectoralis CS activities were significantly positively correlated with M-sum for sparrows, but not for juncos. Thus, myocyte metabolic intensity influences M-sum variation in house sparrows, although the stronger correlation of total (r = 0.495) than mass-specific (r = 0.378) CS activity with M-sum suggests that both pectoralis mass and metabolic intensity impact M-sum. In contrast, neither skeletal muscle masses nor pectoralis metabolic intensity varied with M-sum in juncos. However, heart mass was associated with M-sum variation in both species. These data suggest that drivers of metabolic flexibility are not uniform among bird species.
- 出版日期2014-7-3
