Optical and ultrastructural studies of midgut and salivary glands of first instar of Dermatobia hominis (Diptera: Oestridae).

Midguts and salivary glands of newly hatched larvae (L1) of Dermatobia hominis (L., Jr.) were studied using light and electron microscopy. The larval midgut has a tubular, sinusoidal form and consists of a monolayer of epithelial cells with an underlying basement membrane and a surrounding layer of connective tissue. The fine structure of the midgut shows digestive cells with short microvilli, large nuclei, and cytoplasm containing few visible organelles (mitochondria, rough endoplasmic reticulum, and free ribosomes). In the basal region, the plasma membrane of the cells is folded into a labyrinth area. Hemidesmosomes link the basal surface to the basement membrane and septet junctions are present between adjacent cells. The connective tissue circling the basement membrane contains collagen fibrils, muscle fibers, and tracheal tubes. Prominent nuclei with evident nucleoli occur in the digestive cells. The salivary gland is simple and tubular. It has a monolayer of epithelial cells surrounded by basement membrane and connective tissue. The fine structure of the salivary gland shows epithelial cells, microvilli, secretion into the lumen, septate junctions at the lateral face and a basal labyrinth region. The cell nucleus is large and the cytoplasm contains rough endoplasmic reticulum, ribosomes and mitochondria.