GERMINAL PROLIFERATION CENTER IN THE TESTIS OF DROSOPHILA-MELANOGASTER

Analysis of serial section reconstruction performed on the tips of adult and larval testes reveals a germinal proliferation center populated by three morphologically distinct cell types: apical cells, stem cells, and cyst progenitor cells. The apical cells are assembled into a centrally located structure having the other types of cells radially disposed around it reminiscent of the hub and spokes of a wheel. The stem cells and cyst progenitor cells maintain contact with the central structure throughout the entire cell cycle in such a way that one of the two products of their respective mitotic divisions remains associated with the hub as a stem cell or cyst progenitor cell and the other becomes a primary spermatogonium or a cyst cell. Two cyst cells envelop a single primary spermatogonium, and from this association of three cells a bundle of 64 mature sperm will ultimately develop. © 1979 Academic Press, Inc.