尼罗罗非鱼精子形成中核内囊泡的释放

通过透射电镜观察了尼罗罗非鱼的精子形成过程。尼罗罗非鱼精子细胞在成熟过程中，细胞核中出现由双层生物膜构成的囊泡。囊泡中均匀分布着电子密度低的物质。该囊泡逐渐从细胞核内排到细胞核外。在此过程中细胞核不但排出不参与染色质浓缩的物质，还将多余的核膜排出。进入袖套的囊泡可以留在精子的袖套中，而排到核前方和核侧面的囊泡继续以出芽的方式排出精子细胞。尼罗罗非鱼成熟精子的头部仅有染色质高度浓缩的细胞核。细胞核前

THE RELEASE OF VESICLES FROM THE NUCLEUS OF TILOPIA NILOTICA SPERMATID DURING SPERMIOGENESIS

There are bilayer membrane vesicles within the nucleus of spermatid during the spermiogenesis of Tilopia nilotica. Homogeneous low electron dense substance can be seen within the vesicles. The vesicles are dischargeded gradually. At first the outer membrane of the vesicle fuses with the inner nuclear membrane,so the vesicle enters the perinuclear space. Then the vesicle protrudes outwards. The outer nuclear membrane forms a stalk at the base of the vesicle. Finally the vesicle stalk breaks and the vesicle separates from the nucleus. During the release process of the vesicle, which is similar to the budding process in the trans Golgi network. the nucleus gets rid of not only the substance not participating in the condensation of the chromatin but also the redundant nuclear envelope. The vesicles that enter the sleeve of the spermatid may be contained in that of mature spematozoon. Those which are located anterior or lateral to the nucleus will be further discharged from the spermatid by a similar way as budding. There is only highly condensed nucleus in the head of mature spermatozoon of Tilopia nilotica . The sperm lacks an acrosome in its head. The midpiece connects with the posterior end of the nucleus. The centriolar complex, which is located in the implantation fossa, consists of basal body and degenerated proximal centriole. The sleeve can be divided into two parts: the proximal part and the distal part. The proximal part of the sleeve is bilaterally symmetrical. It contains mitochondria, vesicles discharged from the nucleus and redundant nuclear envelope. The distal part of the sleeve may contain the redundant nuclear envelope. The flagellum, the tail of the spermatozoon, stretches out of the central space of the sleeve. There are lateral fins on the flagellum.