鸟类飞羽羽轴髓质结构的定量分析

鸟类飞羽羽轴机械性能一部分来自髓质,但是髓质泡沫结构如何影响羽轴机械性能的问题仍未被研究。本文对5种鸟类初级飞羽羽轴的髓质形态结构进行研究,测定了腔室的大小、壁厚度等形态计量学参数,分析了这些结构参数与体重的关系以及腔室在抵抗形变的作用过程。结果显示,髓质腔室断面的平均周长(l,表示腔室的大小)介于74.26±11.27～153.02±59.01μm之间,在一些种类(如丹顶鹤和毛脚鵟),外周髓质的l值显著大于中央髓质(P<0.05),而在另一些种类(鸿雁、银鸥和短耳鸮)择二者差异不显著(P>0.05);腔室壁厚度(t)介于0.51±0.15～2.14±1.11μm之间,在所有种类外周髓质的t值均显著(P<0.05)或极显著(P<0.01)大于中央髓质。l和t之间没有显著的相关性(P>0.05),但是外周髓质的t值与翈面面积、体重均呈显著的线性相关(P<0.05)。上述结果表明,空球形腔室可以把某一点上的压力有效地传递和分配到整个羽轴内部,并在每个形变的腔室壁上积累势能;外周髓质对羽轴机械性能的贡献大于中央髓质,这种贡献主要缘于腔室壁的厚度而不是腔室的大小。但是,腔室大小在不同鸟类显出与扑翼强度相一致的关系。

A Morphometric Analysis of the Rachis Medulla of Primary Feathers

The mechanical function of the feather rachis shaft is partly due to the medulla,a bubble - like structure.However, it remained unknown how the bubble structure influences mechanical properties and functions.We studied the structure of the rachis medulla of the primary feathers of 5 bird species using morphometric indices including the perimeter of bubbles（l） and the thickness of the bubble wall（t）.Bubble perimeter was from 53.02±59.01 to 74.26±11.27 urn.Bubble perimeter of the outer medulla was significantly greater than that of central medulla in the red crowned crane（Grus japonensis） and rough legged buzzard（Buteo lagopus）（P0.05 ）,while in the swan goose（Anser cygnoides）,short - eared owl（Asio flammeus）, and herring gull（Larus argentatus ）,the difference was not significant（P0.05 ）.Thickness of the bubble wall ranged from 0.51±0.15 to 2.14±1.11μm.Thickness of the outer medulla was significantly higher than that of the central medulla in all species（P0.05 ）.No correlation was observed between l and t（P0.05 ）.However,l of the outer medulla was significantly correlated with vane area and body mass（P0.05）.These results suggest the bubble structure is capable of distributing force on it to the entire medulla of the rachis and of accumulating potential energy to recover the structure. The outer medulla makes a larger contribution to rachis mechanical properties than does the central medulla due to the greater wall thickness of the former but not the size of its bubble.However,variation of bubble size across species showed a correlation with flapping strength.