Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa.
Theriogenology. 2012 Sep 15;78(5):1094-101. doi: 10.1016/j.theriogenology.2012.04.018. Epub 2012 Jul 3.
Multiflagellate sperm represent a rare defect in mammals and also in the emu where an incidence of only 1% multiflagellate sperm was recorded in semen samples from 15 birds. Biflagellate sperm were the most frequent form of the defect observed, but 3- to 5-tailed sperm were also noted. An association was apparent between multiple tails and macrocephalic sperm, which accounted for 0.6% of multiflagellate sperm. Structural features of the defect were generally similar to those seen in mammals. The duplicated tails shared a single midpiece, which housed supernumerary centriolar complexes, each surrounded by a mitochondrial sheath. A single row of mitochondria separated adjacent centriolar complexes. Elements of the connecting piece (segmented columns, capitellum) appeared normal. The nuclear base appeared flat, staggered, or scalloped depending on the number and depth of additional implantation fossae. Multiflagellate emu sperm of normal head dimensions displayed a widened nuclear base (in the form of an attenuated peripheral nuclear extension) to accommodate the attachment of the additional centriolar complexes. Defective mammalian sperm do not show this modification of the nuclear base as the inherently wider sperm head is able to accommodate the supernumerary centrioles. Although often spiraled around each other, the duplicated principal pieces of the tail were generally separated and free. However, in some cells the proximal parts were collectively bound within the plasmalemma. Multiflagellate sperm appear to have a dual origin with some defective cells originating from incomplete cytokinesis and others as a result of abnormal centriolar duplication.
多鞭毛精子在哺乳动物中较为罕见，在鸸鹋中也存在这一现象，在对 15 只鸸鹋的精液样本进行检测后发现，仅有 1%的精子存在多鞭毛缺陷。双鞭毛精子是观察到的最常见缺陷形式，但也有 3-5 尾的精子。多尾与大头精子之间存在明显关联，大头精子约占多鞭毛精子的 0.6%。缺陷的结构特征通常与哺乳动物中观察到的相似。复制的尾部共享单个中段，其中包含多余的中心粒复合物，每个复合物都被线粒体鞘包围。一排单独的线粒体将相邻的中心粒复合物隔开。连接段的元素（分段柱、顶体）看起来正常。核基底根据额外植入窝的数量和深度，呈现平坦、交错或扇形。具有正常头部尺寸的正常多鞭毛鸸鹋精子显示出增宽的核基底（表现为外围核延伸减弱），以适应额外中心粒复合物的附着。有缺陷的哺乳动物精子没有显示出这种核基底的修饰，因为本身较宽的精子头部能够容纳多余的中心粒。尽管多鞭毛精子的尾部通常相互缠绕，但复制的主段通常是分开的和自由的。然而，在一些细胞中，近端部分在质膜内集体结合。多鞭毛精子似乎具有双重起源，一些有缺陷的细胞起源于不完全的胞质分裂，而另一些则是由于中心粒异常复制。
