Lillywhite Harvey B, Seymour Roger S
Department of Biology, University of Florida, Gainesville, Florida 32611, USA.
Physiol Biochem Zool. 2011 Jan-Feb;84(1):99-101; discussion 102-6. doi: 10.1086/658082.
Here we comment on a recent article (Gartner et al. 2010 ) that addresses previous adaptive interpretations of heart position in the context of gravity effects on blood circulation of snakes. The authors used phylogenetically based statistical methods and concluded that both habitat and phylogeny influence heart position, which they contend is relatively more posterior in arboreal compared to terrestrial species. Their result is based on measurements of heart position relative to snout-vent length, rather than total body length as in previous studies. However, gravity acts on the total length of the arterial-venous vasculature, and caudal segments of continuous blood columns cannot be ignored. Arboreal snakes have relatively long tails; therefore anterior hearts appear to be more "posterior" when the position is described relative to a shorter trunk. There is no physiologically valid explanation for the alleged posterior heart position in arboreal snakes, and multiple lines of published evidence to the contrary are ignored. The authors secondarily evaluated their data set with estimates for total body length based on measurements from other taxa. They found no statistical difference between heart position in arboreal versus terrestrial species, yet their article implied otherwise. Gartner et al. ( 2010 ) contrasted "aquatic" and terrestrial species throughout their paper, and they claimed there is no correlation between heart position and habitat among "aquatic and terrestrial species." But they did not include any aquatic species in their data set. Therefore, the article confuses rather than promotes understanding of cardiovascular adaptation to gravity.
在此，我们对最近一篇文章（Gartner等人，2010年）进行评论，该文章探讨了先前在重力对蛇血液循环影响的背景下对心脏位置的适应性解释。作者使用基于系统发育的统计方法，得出栖息地和系统发育都会影响心脏位置的结论，他们认为与陆栖物种相比，树栖物种的心脏位置相对更靠后。他们的结果是基于心脏位置相对于吻肛长度的测量，而不是像先前研究那样基于总身体长度。然而，重力作用于动静脉血管系统的总长度，连续血柱的尾部段不能被忽视。树栖蛇的尾巴相对较长；因此，当相对于较短的躯干描述位置时，靠前的心脏似乎更“靠后”。对于树栖蛇所谓的靠后心脏位置，没有生理学上合理的解释，而且多条已发表的相反证据被忽视了。作者其次用基于其他分类群测量的总身体长度估计值来评估他们的数据集。他们发现树栖物种和陆栖物种的心脏位置之间没有统计学差异，但他们的文章却暗示了相反的情况。Gartner等人（2010年）在整篇论文中对比了“水生”和陆栖物种，他们声称“水生和陆栖物种”的心脏位置与栖息地之间没有相关性。但他们的数据集中没有包括任何水生物种。因此，这篇文章与其说是促进了对心血管对重力适应性的理解，不如说是造成了混淆。
