Abstract
The germline cells in the ovary of the female bee are interconnected by intercellular bridges kept open by cytoskeletal reinforcements in the plasmic membrane. These bridges among the germline cells display a dynamic behavior and probably act in the determination of the oocyte among the cells of the clone formed by the premeiotic mitoses, subsequently forming a pathway that enables the products synthesized by the nurse cells to reach the oocyte during its maturation. The cytoskeletal elements in the intercellular bridges of bee gonads are basically microfilaments and microtubules, but another type of filament (thick, of non-defined nature, associated with elements of the endoplasmic reticulum) is present in the bridges between the premeiotic cystocytes. This filament crosses the bridge, using microfilaments to fasten itself to the plasmic membrane. These filaments appear to control the span of the bridge. Upon completion of the proliferation phase the cystocytes take on a rosette shape, and a fusome formed by the convergence of the bridges appears at their center. The thick filaments are not present in this conformation. The differentiation of the oocyte and the nurse cells leads to a new change, in which the bridges are reoriented to convey the content of the future nurse cells to the oocyte.
Highlights
The substances exchanged among the cells that make up a tissue, an organ, or the organism as a whole are essential for its harmonious operation and for determining the specificity of its functions
The bridges interconnecting the germ cells in the ovarian cysts, which result from mitosis with incomplete cytokinesis occurring during the proliferative phase of the secondary oogonia, link sister cells – the cystocytes (Fig. 1)
This condition is due to the small amount of cytoplasm in these cells (Figs. 1a and 1b). These bridges contain two types of reinforcements: 1) electron-dense microfilaments arranged in a ring immediately beneath the plasma membrane, forming a belt around the bridge area, and 2) thick filamentous n f m n rb f n n rer a b n mt mt m n chr c d reinforcements intercalated with cisternae of the rough endoplasmic reticulum, which cross the bridges and are bound to the area of the membrane reinforced with microfilaments (Fig. 1b)
Summary
The substances exchanged among the cells that make up a tissue, an organ, or the organism as a whole are essential for its harmonious operation and for determining the specificity of its functions. In female insects with meroistic ovaries, each primary oogonium in the germarium is divided by mitosis, thereby resulting in two cells One of these cells preserves its identity as a primary oogonium or stem cell, while the other differentiates into a secondary oogonium, called a cystoblast or mother cell, which produces cystocytes by successive cellular divisions with incomplete cytokinesis. These cells, which are interlinked by cytoplasmic bridges, constitute the cysts in the germarium (Cassidy & King, 1972; Cruz-Landim, 1978; King & Akai, 1982; Staurengo Da Cunha, 1981; Zacaro & Cruz-Landim, 1996; Zacaro, 1999). The nurse and oocyte cells belong to the same line; they are clones resulting from the differentiation of cells in the same cyst
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