STRUCTURAL CHARACTERIZATION OF MUSCLES AND EPITHELIAL SHEATHS OF THE OVIDUCT OF STOMOXYS-CALCITRANS (DIPTERA, MUSCIDAE)

Fine structure of both muscle and epithelial cells in the oviduct of S tomoxys calcitrans (L.) was characterized. Each tubular section of the oviduct consisted of an inner epithelial sheath enveloped by an outer network of muscle fibers that shelved noticeable variation in cross-s ectional thickness. Some regions consisted of a single cellular layer whereas others were composed of two or more layers of cells. Moreover, a wide variation in muscle fiber orientation was observed, with some cells appearing circular and others appearing nearly longitudinal. The myofibrils of oviduct muscles were separated into sarcomeres of irreg ular alignment. The classical A (1 mu m in length) and I bands of myof ilaments were evident, but the Z disk consisted of discontinuous rows of dense bodies. In partially contracted muscle cells, some myofilamen ts of the A band passed between the dense bodies of the Z band. T-syst em tubules were evident and formed dyads with sarcoplasmic reticulum. The structural integrity of the oviduct was maintained by connective t issue strands between muscles and the epithelial sheath. Many of these strands consisted of basal lamina. Epithelial cells that line the inn er sheath of the oviduct were cuboidal. In transection, these cells re vealed a prominent apical microvillar region xith large numbers of mit ochondria and an extensive infolding of the basal plasma membrane.