Peritrophic membrane structure and formation of larval Trichoplusia ni with an investigation on the secretion patterns of a PM mucin

Peritrophic membrane or matrix (PM) secretion and formation patterns were e xamined in the cabbage looper larvae (Trichoplusia ni [Hubner]) by transmis sion and scanning electron microscopy (SEM), PM first became visible in the lumen between tips of the microvilli and the stomodeal valves as a single layered fibrous structure that became more compact in appearance in the mid dle and posterior mesenteron. In the anterior mesenteron, nascent PM was vi sible within the brush border as a fibrous linear structure that contained both the major PM matrix protein, invertebrate intestinal mucin (IIM) and c hitin-containing structures. Even though delamination events were confined to the anterior mesenteron, IIM was secreted by columnar epithelial cells t hroughout the length of the mesenteron, SEM of the midgut epithelium reveal ed PM covering individual epithelial cells.