Data from: Lower haematocrit, haemoglobin and red blood cell number in zebra finches acclimated to cold compared to thermoneutral temperature

Thermoregulation constitutes an important share of the energy budget of endotherms. Elevated thermoregulatory requirements must be met by oxygen supply through the blood, as heat is produced mainly via aerobic processes. In contrast to mammal studies, it remains unclear whether elevated thermoregulatory needs are followed by changes in haematological variables in birds. We investigated haematocrit (HCT), haemoglobin content per volume of blood (HGB), number of red blood cells (RBC), and size of the erythrocytes (RBC) in zebra finches (Taeniopygia guttata) acclimated to either cold or thermoneutral ambient temperatures under laboratory conditions. Seventy-nine females were maintained for six weeks either in cold (T = + 12 °C) or thermoneutral (T = + 32 °C) ambient temperature prior to blood collection. On average, HGB, HCT and RBC were significantly lower by about 10% in cold acclimated compared to thermoneutral acclimated birds. Only RBC was not different between the two acclimation temperatures. Mean HCT, one of the most commonly measured haematological variable for example was 53 ± 0.9 % (LSM ± s.e.m) in thermoneutral and 49 ± 0.8 % (LSM ± s.e.m) in cold acclimated zebra finches. On first sight, the observed lower values for three out of the four determined haematological variables in response to acclimation to cold question oxygen supply to be indeed a limiting factor for heat production. However, higher demands of oxygen supply due to increased thermoregulation in birds may instead require specific optimisation of blood viscosity and modulation by other cardiovascular properties. Nucleated red blood cells in birds may pose different strain on blood viscosity compared to non-nucleated mammalian erythrocytes and explain the contrasting response in haematological variables to temperature acclimation between birds and mammals.体温调节（thermoregulation）在内温动物（endotherms）的能量收支中占据重要比例。由于热量主要通过有氧代谢过程产生，升高的体温调节需求必须依靠血液的氧气供应来满足。与哺乳动物相关研究不同，目前尚不清楚鸟类体温调节需求升高时，其血液学指标是否会发生相应变化。我们在实验室条件下，对分别适应寒冷或热中性环境的斑胸草雀（Taeniopygia guttata）的血细胞比容（HCT）、每单位体积血液血红蛋白含量（HGB）、红细胞（RBC）数量以及红细胞体积进行了检测。共纳入79只雌性斑胸草雀，在采血前将其分别置于寒冷环境（温度为12℃）与热中性环境（温度为32℃）中饲养6周。结果显示，与热中性环境适应组相比，寒冷适应组的HGB、HCT及RBC数量平均降低约10%，且差异显著；仅RBC数量在两组间无显著差异。以最常用的血液学指标之一——平均血细胞比容为例，热中性环境适应组斑胸草雀的HCT为53±0.9%（最小二乘均值±标准误，LSM ± s.e.m），寒冷适应组为49±0.8%（LSM ± s.e.m）。乍看之下，寒冷适应组四项血液学指标中有三项的观测值降低，这不禁让人质疑氧气供应是否确实为产热过程的限制因素。然而，鸟类因体温调节增强而产生的更高氧气供应需求，反而可能需要通过优化血液粘度以及调节其他心血管功能来满足。与无核的哺乳动物红细胞相比，鸟类的有核红细胞对血液粘度的影响存在差异，这或可解释鸟类与哺乳动物在温度适应过程中血液学指标响应的差异。