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.体温调节在恒温动物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，体温调节需求的提升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，目前尚不清楚鸟类在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，对驯化于寒冷或热中性环境的斑胸草雀（*Taeniopygia guttata*）开展了相关研究，检测的血液学指标包括血细胞比容（haematocrit, HCT）、单位体积血液血红蛋白含量（haemoglobin content per volume of blood, HGB）、红细胞（red blood cells, RBC）数量以及红细胞大小（erythrocytes, RBC）。本研究共纳入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℃）中驯化6周。平均而言，与热中性环境驯化的个体相比，寒冷环境驯化的斑胸草雀的HGB、HCT及RBC水平平均降低约10%；仅红细胞数量在两种驯化温度下无显著差异。以最为常用的血液学指标之一的血细胞比容为例，热中性环境驯化的斑胸草雀的平均血细胞比容为53±0.9%（LSM±s.e.m），寒冷环境驯化个体则为49±0.8%（LSM±s.e.m）。乍看之下，寒冷驯化下四项检测的血液学指标中有三项水平降低，这似乎对“氧气供应确实是热量产生的限制因素”这一观点提出了质疑。然而，鸟类因体温调节增强而产生的更高氧气供应需求，反而可能需要对血液粘度进行特异性优化，并通过其他心血管特性进行调节。与无核的哺乳动物红细胞相比，鸟类的有核红细胞可能对血液粘度产生不同的影响，这或可解释鸟类与哺乳动物在血液学指标对温度驯化的响应方面存在的差异。