![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Summary
The testes of the newly hatched larva of Oncopeltus fasciatus consist of three different cell types enclosed by the tunica propria: the germline stem cells, the apical cells, and the follicle border cells which are the predecessors of the cyst progenitor cells. There are usually twelve somatically derived apical cells per follicle that no longer divide during postembryonic development. Their fine structural organization remains constant from hatching until death from old age. The apical complex cells are surrounded by at least four germline stem cells which all send cell projections toward the apical complex cells. A testicular follicle includes at least four border cells at the first larval instar. Follicle border cells are of somatic origin and are noticeably electron lucent due to a paucity of cells organelles, in particular of free ribosomes. Whereas the cells are at first evenly distributed around the follicle, toward the end of the second larval stage they aggregate to form a monolayer at the apical end of the follicle, between the tunica propria and germline stem cells. This marks the transition of the follicle border cells to cyst progenitor cells. The first spermatogonial cysts are formed at the end of the second larval stage. The course of cyst formation remains the same throughout the following larval stages and the whole adult life. Detailed studies were carried out during the fourth larval stage. Apical germline stem cells are in intimate contact with cyst progenitor cells. Since several cyst progenitor cells usually contact an individual germline stem cell, a firm one-to-one relationship is difficult to demonstrate, although it might exist. Spermatoblasts separate somewhat laterally from the apical part of the rosette of germline stem cells. They are devoid of cell projections and become enclosed by one cyst cell which no longer divides. Whereas the cyst cell enlarges as spermatogenesis proceeds, the nucleus grows endomitotically, and becomes large and triangular in profile. The cyst cells—still very electron lucent—present a conspicuous subcellular organization. They contain several Golgi complex-like elements with extended longitudinal axes. These elements consist of a few cisternae and mainly of short branching interconnected tubules and vesicles. A sparsely granulated endoplasmic reticulum is located between and in close contact with the Golgi complex-like elements. The significance of the extraordinary subcellular organization is unknown. A role of the cyst cells in the regulation of spermatogenesis is discussed.