似锥低颈吸虫的精子和精子形成的超微结构研究（复殖目：棘口科）

似锥低颈吸虫（Ｈｙｐｏｄｅｒａｅｕｍｃｏｎｏｉｄｅｕｍ）的成熟精子分为前段和主段。前段含两条鞭毛轴丝和一圈连续纵向排列的膜下微管；主段含两条不等长鞭毛轴丝、核、线粒体、糖原，背侧和腹侧的膜下微管。在精子形成过程中，精子细胞出现胞质突起，核与胞质突起部的质膜之间出现特殊分化区域（ＺＤ）。特殊分化区域的组成包括质膜下一排膜下微管，两个具有横纹小根的中心粒和１个中心粒间体（Ｉｎｔｅｒｃｅｎｔｒｉｏｌａｎｂｏｄｙ）。鞭毛从中心粒伸出，延伸，与中间不断伸长的胞质突起平行，核旋转，拉长，与细长的线粒体前后进入胞质突起，最后鞭毛从近端到远端（Ｐｒｏｘｉｍｉｔｏｄｉｓｔａｌｌｙ）与中间胞质突起融合，并从精子细胞群上脱落，形成成熟精子，遗留下精子细胞群的残体。残体（Ｒｅｓｉｄｕａｌｂｏｄｙ）上含弓形膜结构，线粒体，鞭毛轴丝残余以及电子致密颗粒，在一个残体上，至少有１０个以上的精子断端。

ULTRASTRUCTURE OF SPERM AND SPERMATOGENESIS OF HYPODERAEUM CONOIDEUM,BLOCH 1872(TREMATODA: DIGENEA: ECHINOSTOMATIDAE)

Mature sperm of Hypoderaeum conoideum exhibit the structure typical of trematoda of Digenea.The mature spermatozoon is identified as two regions,the anterior region originates from the ZD,it usually has a continuous circle of peripheral microtubules and 2 axonemes of the 9 1 pattern being incorporated into the sperm body. The principal region contains the nucleus and mitochondrion,the two incorporated axonemes, and microtubules located only on the ventral and dorsal faces. The nucleus is posterior and the centrioles are anterior. The length of the axonemes is not same. DUring spermiogenesis,a zone of differentiation (ZD) develops that comprises a row of microtubules along the cell membrane,the intercentriolar body and centrioles appear between the microtubules and the nucleus. Free flagella with striated rootlets grow out in parallel directions,the cell membrane protrudes and lengthens into a median cytoplasmic process(MCP),the nucleus rotates lengthen,then penetrates the ZD and move into the MCP,the mitochondrion make the same change as nucleus. The two flagella eventually fuse with the MCP. The fusion progresses from the basal(proximal) extremity to the distal extremity,therefore it may be termea proximodistal. The spermatid elongates and finally pinched off from the residual body at the level of the arching membranes after the rootlets and intercentriolar body have disppeared. The residual body contains the profiles of arching membrances,mitochondria,remnant axonemes and some electrodense bodies.There are more than ten remnant ends of sperms in one residual body.