A espermiogenese em Boophilus microplus (Canestrini, 1887) (Acari:ixodidae) : aspectos estruturais e ultra-estruturais

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The objective of this study was to describe the spermatogenesis of the cattle tick (Boophilus microplus) (Canestrini, 1887), based on histological, histochemical, morphologic and ultrastructural infromation. Spermatogenesis occurs in the testis of ticks which begin their blood repast. The gametic cell lineage is isolated in cysts. Spermiogenesis begins in the male and is concluded in the reproductive ducts of young females. Encysted spermatocytes, after the growth phase, pass through meiosis and differentiate into round spermatids, then elongated spermatids. In the female organism, the elongated spermatids are transformed into spermatozoa. Spermatogenesis involves the fusion of vesicles situated just below the plasmic membrane, called the sub-surface cisternae, leading to the formation of the cisternal cavity. This cavity is formed by the concentration of cisternae in the pole opposite to the nuclear region. This process was called polarization and it originates the polarized spermatids. The cisternae apparently develope from a transformed endoplasmic reticulum; these tubules have very dense membranes. They have a glicoproteinaceous content, and give an argentophylic reaction, which gradually increases during differentiation. In the cytoplasm of round and polarized spermatids, abundant rough endoplasmic reticulum can be seen, and in spermatids engaged in forming their cisternal cavity, there are also many multivesicular bodies. Also, a strongly P.A.S. positive vesicle can be found positioned above the nucleus, which some authors consider to be the acrosome. The round spermatids pass through an elongation, concomitantly with the formation of the cisternal cavity and the latero-posterior positioning of the nucleus. Elongated spermatids are subdivided into three concentrical cilindrical regions by the invagination of the cisternal cavity. The first is the external tube, where the elongated nucleus is lodged. The second is the cisternal cavity which has a progressively dense matrix of glicoproteins. The third compartment, referred to as the internal cilinder, contains many mitochondria. This internal cilinder is the invagination center of the elongating spermatid. The membrane of the cisternal cavity forms innumerable projections, resulting from the fusion of the cisternae. These projections are quite complex, with a fibrous proteic axis, surrounded by the membrane cavity. In the female, the eversion of the spermatids is observed. During this process, the plasmic membrane invaginates,originating the acrosomal canal. This canal is covered by a flattened, elongated cistern-like vesicle, which is apparently derived from the supra-nuclear vesicle, which is rich in glicoproteins and first observed in polarized spermatids. This vesicle is in close contact with the plasmic membrane in elongated spermatids and maintans the same position in relation to this membrane when it lines the canal. At the same time, the eversion of the cisternal cavity occurs, turning this membrane inside out to cover the surface of the spermatozoon. Projections of the cisternal cavity membrane can be observed covering the entire spermatozoon with the exception of two regions: The posterior region which is smooth and the anterior extremity where the projections are very different from those seen on the rest of the spermatozoal surface. These projections are quite simple and rounded with a conspicuous peduncle. The projections appear to be associated with movement, since they are connected to cytoskeletal elements. The cytoplasm of spermatozoa have a clearly separated central region filled with thick filaments, similar to intermediate filaments and a cortical region rich in microfilaments. The nucleus of these cells is posterior and it follows the canal laterally. Mitochondria can be seen dispersed in the cytoplasm of the anterior and medial-anterior portion, while in the medial-posterior and posterior portion of the spermatozoon, they are alined separating the cortical and central regions of the cytoplasm. The motility of the spermatozoon, observed "in vivo", is advancement by torsion

ASSUNTO(S)

histoquimica espermatogenese carrapato-boi

ACESSO AO ARTIGO

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