The sperm tail is composed of axial filament twisted with the lateral fin, and the axial filament is typical 9+2 structure of microtubule.3.
精子尾鞭由轴丝(A)与侧鳍(Lf)缠绕形成，轴丝结构为典型的“9+2”型，侧鳍只位于轴丝的一侧，并围绕着轴丝而扭转。
参考来源 - 瘤背石磺（Onchidium struma）的生物学研究·2,447,543篇论文数据，部分数据来源于NoteExpress
所有这些海洋原始动物都有生长得很完善的侧鳍。
Syrinxdidi: All of these primitive sea creatures had well developed lateral fins.
所有这些海洋原始动物都有生长得很完善的侧鳍。
All of these primitive sea creatures had well developed lateral fins.
一种小枪鱼（条纹四鳍旗鱼或箕作枪鱼），产于太平洋和印度洋，两侧有竖直条纹。
A small marlin (Tetrapturus audex or Makaira audex) of the Pacific and Indian oceans, marked with vertical stripes along the sides.
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