New insights into the spermatogenesis of the black tiger prawn, Penaeus monodon

This study reports a comprehensive description of penaeid spermatogenesis (Penaeus monodon) by light and transmission electron microscopy. A conspicuous characteristic of spermatocytogenesis was a ring-like structure with high electron-density adjacent to the nucleus of a primary spermatocyte. During the spermiogenesis from stage I (StI) to stage VI spermatid (StVI), the formation of the acrosome and decondensation of the nucleus were the most notable morphological transformations. StIs were small and compact and they were contained in the syncytia. In the cytoplasm of StII, mitochondrion-like bodies (MLB) participated the extension of perinuclear multi-layered lamellae. The association of MLBs and endoplasmic reticula appeared to contribute to the formation of small cytoplasmic pre-acrosomal vesicles (PV) which coalesced into an acrosomal chamber (AC) at the periphery of StIII. A dense anterior acrosomal body (AB) was formed in the enlarged AC in StIV. The nuclear envelope became disintegrated in StV. At last, an AB-derived spiky acrosome was emerged from AC in StVI. Sperm nuclei became increasingly decondensed during the entire process of spermiogenesis and the nuclear components in the testicular spermatozoa appeared to only contain chains of DNA and nucleosome-contained chromatin.