Cytoplasmic bridges, intercellular junctions, and individualization of germ cells during spermatogenesis inDermatobia hominis (Diptera: Cuterebridae)

Abstract

During mitotic and meiotic divisions in Dermatobia hominis spermatogenesis, the germ cells stay interlinked by cytoplasmic bridges as a result of incomplete cytokinesis. By the end of each division, cytoplasmic bridges flow to the center of the cyst, forming a complex, called the fusoma. During meiotic prophase I, spermatocytes I present desmosome‐like junctions and meiotic cytoplasmic bridges. At the beginning of spermiogenesis, the fusoma moves to the future caudal end of the cyst, and at this time the early spermatids are linked by desmosome‐like junctions. Throughout spermiogenesis, new and sometimes broad cytoplasmic bridges are formed among spermatids at times making them share cytoplasm. In this case the individualization of cells is assured by the presence of smooth cisternae that outline their structures. The more differentiated spermatids have in addition to narrow cytoplasmic bridges, plasmic membranes junctions. By the end of spermiogenesis, the excess cytoplasmic mass is eliminated leading to spermatid individualization. Desmosome‐like junctions of spermatocytes I and early spermatids appear during the fusoma readjustment and segregations; on the other hand, plasmic membrane junctions appear in differentiating spermatids and are eliminated along with the cytoplasmic excess. These circumstances suggest that belt desmosome‐like and plasmic membrane junctions are involved in the maintenance of the relative positions of male germ cells in D. hominis while they are inside the cysts. © 1996 Wiley‐Liss, Inc.

Morphology of the Male Reproductive System and Spermiogenesis ofDendroctonus armandiTsai and Li (Coleoptera: Curculionidae: Scolytinae)

“…These observations suggest that the production of sperms may continue until maturity. In each cyst, the number of spermatids varies among different species as a result of spermatogonial premeiotic divisions ( Oguma et al 1987 , Quagio-Grassioto and Lello 1996 ). In Coleopterans, the number of sperm/bundle varies from 16 (2 4 ) to 512 (2 9 ), with 256 being the most common quantity ( Jurečić 1988 ).…”

Histomorphological studies of the testis and male genital ducts of Supachai's caecilian, Ichthyophis supachaii Taylor, 1960 (Amphibia: Gymnophiona)

“…,b). Formation of the cytoplasmic bridges during spermatogenesis seems to be evolutionarily conserved among invertebrates and vertebrates (Dym and Fawcett ; Quagio‐Grassiotto and De Lello ; Okura et al . ; Dallai et al .…”

Structure and ultrastructure of spermatozoa of Chrysomya megacephala (Diptera: Calliphoridae)

“…Research shows that for Diptera, the number of spermatids per bundle varies among different species depending on the number of spermatogonial premeiotic divisions (Oguma et al, 1987, Quagio-Grassiotto and Lello, 1996and Cruz-Landim, 2001). For Aedes aegypti (Culicidae), it was suggested by Owusu-Daaku et al (2007), that the maximum number of spermatozoa per cyst for this species is probably 512, being the result of nine divisions from the original spermatocyst mother cell (stem cell), according to what has been proposed by Virkki (1969).…”