Variability in Basal Metabolic Rate of a Long-Distance Migrant Shorebird (Red Knot, Calidris canutus) Reflects Shifts in Organ Sizes
Variability in Basal Metabolic Rate of a Long-Distance Migrant Shorebird (Red Knot, Calidris canutus) Reflects Shifts in Organ Sizes
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DOI：
10.1086/physzool.69.1.30164207
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发表时间：
1996-01
期刊：
影响因子：
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通讯作者：
Theunis Piersmal;Leo Bruinzeel1;Rudolf Drent1;Marcel Kersten1;Jaap Van der Meer2;P. Wiersma;L. T.Pie
中科院分区：
文献类型：
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作者：
Theunis Piersmal;Leo Bruinzeel1;Rudolf Drent1;Marcel Kersten1;Jaap Van der Meer2;P. Wiersma;L. T.Pie
我们研究了两种红滨鹬亚种 Calidris canutus 的身体成分和基础代谢率（BMR，在夜间热中性条件下对吸收后鸟类进行测量）的差异：一种在温带高能量消耗的气候条件下度过非繁殖季节（西欧的 islandica 亚种），另一种在炎热潮湿的热带地区越冬（西非和南非的 canutus 亚种）。为了检验在相同条件下是否存在可能存在的差异，我们将两组动物都圈养起来，并对 10 个“器官”（胸肌、腿部肌肉、胃、肠、肝、肾、肺、心脏、皮肤、骨骼和附着肌肉）的脂肪和瘦肉成分的身体成分进行了量化。圈养鸟类的瘦肉组织比野生鸟类轻，尤其是胃、肠、肾脏和肝脏（营养器官）。在北半球冬季，野生海岛节的瘦肉质量比热带非洲的坎努斯节要高。热带越冬红滨鹬的 BMR 低于温带越冬同种，而长期圈养的鸟类的 BMR 值也低于自由生活的鸟类。每类鸟类（野生或圈养的任一亚种）的平均 BMR 值与瘦体重的群体平均值密切相关。基于经历初期饥饿的红滨鹬的总瘦质量来预测 BMR 遵循同样的关系，因为代谢活跃的组织正在耗尽。这两个亚种在圈养条件下的身体成分趋于相似，这表明红滨鹬个体可能具有相当大的灵活性。我们认为，红滨鹬，可能还有大多数其他长途迁徙鸟类，都拥有能够根据一年中遇到的生态条件和食物类型不断调整的代谢机制。我们进一步认为，瘦体重（功能成分）的变化是代谢生理学季节性调整以适应可变需求水平的工具。体重调整提供了灵活的反应，使红腹滨鹬能够在代谢范围放松的情况下节省每日总代谢消耗，例如在热带地区的冬季。
We studied differences in body composition and basal metabolic rate (BMR, measured in postabsorptive birds under thermoneutral conditions at night) in two subspecies of red knots, Calidris canutus: one that spends the nonbreeding season under energetically costly climatic conditions at temperate latitudes (subspecies islandica in western Europe) and one that winters in the hot and humid tropics (subspecies canutus in West and South Africa). To examine whether the possible differences would be upheld under identical conditions, we kept both groups in captivity as well Body composition was quantified with respect to the fat and lean components of 10 "organs" (breast muscles, leg muscles, stomach, intestine, liver, kidneys, lungs, heart, and the skin, and skeleton and attached muscle). Captive birds had lighter lean tissues than wild birds, especially those of the stomach, intestine, kidneys, and liver (the nutritional organs). During the northern winter wild islandica knots had higher lean masses than canutus knots in tropical Africa. Tropically wintering red knots had lower BMRs than their temperate-wintering conspecifics, and birds in long-term captivity had lower BMR values than their free-living counterparts. Average BMR values per category of birds (wild or captive of either subspecies) were strongly correlated with the group averages of lean mass. Prediction of BMR on the basis of total lean mass of red knots undergoing incipient starvation follows this same relationship because metabolically active tissue is being depleted. That the two subspecies converged to similar body composition in captivity indicates that individual red knots may possess considerable flexibility. We argue that red knots, and probably most other long-distance migrants, have metabolic machinery that is able to adjust continuously, depending on the ecological conditions and food types encountered in the course of the year. We further argue that variation in (functional components of) lean mass is the vehicle for seasonal adjustments in metabolic physiology to variable demand levels. Body mass adjustments offer a flexible response enabling red knots to economize on total daily metabolic expenditure whenever conditions allow a relaxation of metabolic scope, such as during winter in the Tropics.