Dallai Romano, Mercati David, Giusti Fabiola
University of Siena, Department of Evolutionary Biology, Via A. Moro, 2 I-53100 Siena, Italy.
J Struct Biol. 2008 Jan;161(1):43-54. doi: 10.1016/j.jsb.2007.09.004. Epub 2007 Sep 14.
The "zipper line" of Drosophila melanogaster and of Drosophila species characterized by giant spermatozoa (D. hydei, D. kanekoi and D. bifurca) was studied by electron microscopy using conventional thin-sections, lectin labeling and freeze-fracture replicas. In cross sections the membrane specializations are located either at the level of the short cistern close to the large mitochondrial derivative where a small tuft of glycocalyx is visible or, in species characterized by long spermatozoa, along a cistern beneath the plasma membrane. In correspondence of such cistern, the plasma membrane exhibits a thick and extended glycocalyx. At this level, as well as at the short tuft of D. melanogaster, alpha-mannose residues were detected. The "zipper" of D. melanogaster consists of rows of intramembrane particles longitudinally disposed along the sperm tail and associated with the external face of the plasma membrane. On the protoplasmatic face a narrow ribbon of transversal grooves is visible. Freeze-fracture replicas have revealed, in the region characterized by extended glycocalyx, the presence of a large ribbon of intramembrane particles disposed in parallel transversal rows, associated with the protoplasmatic membrane face. On the complementary external face a ribbon of parallel transversal grooves was observed. It is suggested that membrane specializations are mechanical devices to protect spermatozoa from torsion and bending in the seminal vesicles and then in the female storage organ.
利用传统超薄切片、凝集素标记和冷冻蚀刻复型技术，通过电子显微镜对黑腹果蝇以及以巨型精子为特征的果蝇物种（海德氏果蝇、金井氏果蝇和分叉果蝇）的“拉链线”进行了研究。在横切面上，膜特化结构要么位于靠近大的线粒体衍生物的短池水平，在那里可见一小簇糖萼；要么在以长精子为特征的物种中，沿着质膜下方的一个池分布。与这样的池相对应，质膜呈现出厚且延伸的糖萼。在这个水平以及黑腹果蝇的短簇处，检测到了α - 甘露糖残基。黑腹果蝇的“拉链”由沿精子尾部纵向排列并与质膜外表面相关联的成排膜内颗粒组成。在原生质面上可见一条狭窄的横向凹槽带。冷冻蚀刻复型显示，在以延伸的糖萼为特征的区域，存在一条由平行横向排列的膜内颗粒组成的大带，与原生质膜面相关联。在互补的外表面观察到一条平行横向凹槽带。有人提出，膜特化结构是一种机械装置，用于保护精子在精囊以及随后在雌性储存器官中免受扭转和弯曲。
