Structure and development of ovaries in the weevil, Anthonomus pomorum (Coleoptera, Polyphaga). II. Germ cells of the trophic chamber
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The analysis of the germ cell cluster formation in Anthonomus pomorum (Coleoptera, Polyphaga, Curculionidae) has revealed that both linear and branched clones of cystocytes occur in the pupa stage. In the branched clones a poorly developed polyfusome is formed and cystocytes with maximally 3 intercellular bridges were found. In the linear clones the polyfusomes are absent. Further divisions of cystocytes produce exclusively linearly arranged cells. Just after metamorphosis (Imago-A stage), the process of the germ cell membrane reduction starts. Only 2 groups of cells retain cell membranes: i.e the most anteriorly localized group of cystocytes and the posteriorly located presumptive oocytes. The former cells divide mitotically during the summer. As a result an anterior-posterior gradient of the syncytialization process arises in the Imago-B stage (females preparing for hibernation). In the sexually mature females (Imago-C) the trophic chamber consists of a huge syncytial area with numerous nurse cell nuclei embedded in a common cytoplasm, and posteriorly located young oocytes surrounded by prefollicular cells. In the light of recent hypothesis concerning the germ cell cluster formation and telotrophy anagenesis in Polyphaga the significance of the presented results is discussed.
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