1、鸟类基础代谢率的主要影响因素基础代谢率(basal metabolic rate, BMR)是恒温动物维持正常生理机制的最小产热速率,是动物在清醒时维持身体各项基本功能所需的最小能量值。除了特殊情况下的无氧代谢,生物体产生的热量与消耗的氧气成正比 1,2(Bicudo et al., 2002; Burton Weathers, 1997) 。近几十年来鸟类基础产热的研究一直是人们热切关注的主题之一,2006 年 3 月召开的第二届Physiology and Pharmacology of temperature regulation国际学术讨论会,鸟类基础产热的研究仍然是一个主要议题。影响
2、鸟类基础产热的因素很多,包括气候、季节和食物等外部环境因素,也包括激素、器官和线粒体的理化特征等内部因素 17,18,19(Baldwin et al., 1980; Lovegrove, 2003; McKechnie Villarin et al., 2003) 。在基础状态下,肝脏可占据总代谢的 20-25%, 27,28(Steffen 和 Roberts, 1977; Rolfe 和 Brown, 1997) 。由于骨骼肌约占体重的40%,在有氧代谢中,主要的氧气消耗和 ATP 的合成发生在骨骼肌线粒体中,因此它也是机体代谢产热的主要贡献者之一。Daan29(1990)认为,体重相近
3、的不同物种,其 基础代谢 差异可能反映了产生高的非基础代谢所必需的“代谢机器”(metabolic machinery)的进化(这些非基础代谢是指在繁殖、冷暴露和可恢复的运动期间的能量需求)。根据这一假设,基础代谢反映了那些产生高代谢率的组织或器官的维持消耗,这些器官可能包括把能量转化为可利用形式的器官肝脏,能量运输器官心脏和排泄最终废物的器官肾脏等 30,31(Konarzewski et al., 1995; Starck & Beese, 2001.)。Daan 29(1990)同时指出,虽然这些器官的重量仅占体重的一小部分,但单位重量组织的代谢活性很高,对基础代谢有相对较大的贡献 32
4、(McWilliams & Karasov, 2001)。Daan 29(1990)统计了 22 种鸟的数据,发现心脏和肾脏的组织重量能够反映基础代谢的差别,因而推断基础代谢率的种间差异是代谢活性器官重量差异造成的。目前不同器官对基础代谢的尚存争议,对这些问题的研究将加深我们对鸟类基础产热的认识,充实生理生态学的理论及其进化意义。5 体重在所有这些影响因素中,毫无疑问体重的影响最为重要。其它各种因素对动物 BMR 的影响因种而异。BMR 与体重的关系是异速增长关系(allometry)。即体重较小的动物其单位体重的 BMR 相对较大。BMR 与体重之间的关系已受到众多研究者的广泛研究。一般认为
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