Spermatogenesis and distinctive mature sperm in the giant freshwater prawn, Macrobrachium rosenbergii (De Man, 1879)

摘要: Abstract The structures of differentiating male germ cells in the testis giant freshwater prawn, Macrobrachium rosenbergii , were studied by light and electron microscopy. Based on ultrastructural characteristics, developing are classified into 12 stages, including spermatogonia, six phases primary spermatocytes (leptotene, zygotene, pachytene, diplotene, diakinesis metaphase), secondary spermatocyte, three stages spermatids mature sperm. During spermatogenesis, have characteristics similar to those other invertebrates, but they exhibit some unique during spermiogenesis. In particular, an early spermatid has a round nucleus with highly condensed heterochromatin, appearing as thick interconnecting cords throughout nucleus. contrast most invertebrates vertebrates, chromatin begins decondense one-half at mid stage. late spermatid, becomes almost entirely decondensed only small crescent-shaped heterochromatin patch remaining anterior pole Mature sperm possess everted umbrella-shaped plate spike covering nucleus, whose is totally traces histones H3 H2B remain. acrosome appears ruffled border sac-like structures. Few mitochondria remain cytoplasm posterior pole.