Jagiellonian University, Institute of Environmental Sciences, Kraków, Poland.
Biol Lett. 2010 Dec 23;6(6):792-6. doi: 10.1098/rsbl.2010.0288. Epub 2010 May 12.
We examined cell size correlations between tissues, and cell size to body mass relationships in passerine birds, amphibians and mammals. The size correlated highly between all cell types in birds and amphibians; mammalian tissues clustered by size correlation in three tissue groups. Erythrocyte size correlated well with the volume of other cell types in birds and amphibians, but poorly in mammals. In birds, body mass correlated positively with the size of all cell types including erythrocytes, and in mammals only with the sizes of some cell types. Size of mammalian erythrocytes correlated with body mass only within the most taxonomically uniform group of species (rodents and lagomorphs). Cell volume increased with body mass of birds and mammals to less than 0.3 power, indicating that body size evolved mostly by changes in cell number. Our evidence suggests that epigenetic mechanisms determining cell size relationships in tissues are conservative in birds and amphibians, but less stringent in mammals. The patterns of cell size to body mass relationships we obtained challenge some key assumptions of fractal and cellular models used by allometric theory to explain mass-scaling of metabolism. We suggest that the assumptions in both models are not universal, and that such models need reformulation.
我们研究了组织间的细胞大小相关性以及雀形目鸟类、两栖动物和哺乳动物的细胞大小与体重的关系。在鸟类和两栖动物中，所有细胞类型之间的大小相关性都很高；哺乳动物组织按三种组织群的大小相关性聚类。在鸟类和两栖动物中，红细胞大小与其他细胞类型的体积相关性很好，但在哺乳动物中则不然。在鸟类中，体重与包括红细胞在内的所有细胞类型的大小呈正相关，而在哺乳动物中仅与一些细胞类型的大小呈正相关。哺乳动物红细胞的大小仅与最具分类学均匀性的物种群（啮齿动物和兔形目动物）的体重相关。鸟类和哺乳动物的细胞体积随体重的增加而增加不到 0.3 次幂，表明体型主要通过细胞数量的变化而进化。我们的证据表明，决定组织中细胞大小关系的表观遗传机制在鸟类和两栖动物中是保守的，但在哺乳动物中则不那么严格。我们得到的细胞大小与体重关系的模式挑战了分形和细胞模型在解释代谢质量缩放时所依据的一些关键假设。我们认为，这两个模型的假设并不普遍，需要对这些模型进行重新表述。
