Peritrophic membrane formation and cellular turnover in the midgut of Culiseta melanura (Diptera: Culicidae).

Midguts of the mosquito Culiseta melanura (Coquillett) were examined by light and electron microscopy at varying intervals after blood feeding. Peritrophic membrane deposition first appeared 6 h after engorgement as a thin, electron-translucent band adjacent to epithelial cells throughout the abdominal midgut and reached maximum thickness at 12 h. Cell loss was apparently low in the abdominal midgut, with occasional cellular debris detected in the lumen 3-5 d after engorgement. Sloughing of cytoplasmic dropletlike evaginations, devoid of organelles, occurred infrequently in the abdominal midgut between 5 and 7 d after feeding. In contrast, cellular and cytoplasmic loss occurred continuously in the thoracic midgut. Epithelial cell replacement and regenerative cell mitosis were not detected in the abdominal or thoracic midgut.