四指马鲅精巢发育及精子发生的组织学和超微结构

为了解四指马鲅（）精巢的组织结构和精巢发育及精子发生的组织学和超微结构变化,运用组织切片HE染色和透射电镜技术对养殖四指马鲅的精巢发育过程进行观察。结果显示,四指马鲅精巢位于腹腔背侧,紧贴中肾和鳔的腹面,为一对延长的扁平带状器官,呈灰白色,两条精巢于后端融合,呈“Y”字形,组织学上属典型小叶型精巢;根据精巢发育及精子发生的组织学特点可将其分为6个时期：3月龄精巢发育至第I期（精原细胞增殖期）,4月龄发育至第II期（精母细胞增长期）,5~7月龄发育至第III期（精母细胞成熟期）,7~9月龄发育至第IV期（精子开始出现期）,最早在10月龄发育至第V期（精子完全成熟期）达到初次性成熟;参与生殖排精后的精巢为第VI期（精子退化吸收期）;精子发生过程经历初级精原细胞、次级精原细胞、初级精母细胞、次级精母细胞、精细胞和精子6个时相,其细胞及细胞核直径逐级减小,核质比发生规律性变化;电镜下显示精子发生过程中,细胞核内染色体逐渐浓缩,电子密度增加,线粒体数量减少,体积增大,內嵴结构逐渐丰富;精子由头部、中部和尾部组成,鞭毛轴丝为典型“9+2”结构。本研究阐述了四指马鲅雄鱼精巢的组织结构及初次性成熟精巢发育及精子发生过程的组织学和超微结构变化,丰富了四指马鲅的繁殖生物学内容,为掌握四指马鲅的繁殖规律和提高人工繁育技术提供理论参考。

Histology and ultrastructure of developing testes and spermatogenesis in the fourfinger threadfin, Eleutheronema tetradactylum (Show, 1804)

Reproduction is one of the most important processes in the life history of fish. However, there is little information about the reproductive biology of the fourfinger threadfin, (Show, 1804). In this paper, paraffin tissue sections were used to observe the developmental process of testes via haematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) in order to understand the organizational structure of the testes as well as the histological and ultrastructural changes associated with spermatogenesis during primary sexual maturity in cultured fourfinger threadfin individuals. The results show that the testes are a pair of extended flat zonal organs that are gray in color and fuse at the posterior end into a Y-shape. The organs are located on the dorsal side of the abdominal cavity, attached to the ventral surface of the mesonephros and swim bladder. The developmental process of the testes was divided into six stages defined by histological characteristics. The testes develop to stage I (spermatogonia proliferates), followed by stage II (spermatocyte growth), stage III (spermatocytes mature), and stage IV (sperms begin to appear) at about three months of age, four months of age, five to seven months of age, and seven to nine months of age, respectively. At a minimum of 10 months of age, the testes develop to stage V (complete maturation of sperm) and reach the first stage of sexual maturity. The post-reproductive testes in stage VI (degradation and absorption) were observable after the breeding season. Spermatogenesis went through six phases, namely primary spermatogonia, secondary spermatogonia, primary spermatocyte, secondary spermatocyte, spermatocyte, and sperm in succession. The diameter of cells and nuclei decreased step by step, and the ratio of nucleus to cytoplasm changed regularly. During spermatogenesis, chromosomes in the nucleus were gradually condensed, electron density was increased, and mitochondria were enlarged and aggregated with inner cristae structure gradually enriching. Sperm was composed of a head, middle, and tail. The axial filament of the flagella followed a typical "9+2" structure. This study elaborated on the organizational structural characteristics of the testes and the histological and ultrastructural changes during testes development and the spermatogenesis process of first sexual maturity stage of cultured fourfinger threadfin. This information enriches our collective knowledge on the species'' reproductive biology and provides a theoretical reference for understanding reproduction laws and improving artificial breeding technologies.