PERITROPHIC ENVELOPES OF LUTZOMYIA-SPINICRASSA (DIPTERA, PSYCHODIDAE)

The secretion, morphology, and chemical composition of the peritrophic envelope were studied in the phlebotomine sand fly Lutzomyia spinicra ssa Morales, Osorno-Mesa, Osorno and Hoyos, a suspected vector of Leis hmania braziliensis in Colombia and Venezuela. Viewed under light micr oscopy, the envelope matured rapidly and could be dissected from the b lood bolus as early as 12 h and until 36 h after feeding; subsequently it began to degrade. The envelope was initially a closed sac around t he blood meal, but opened posteriorly in most flies by 6 h. The poster ior opening may facilitate the migration and establishment of La. braz iliensis in the hindgut. Secretion of envelope precursors was from the entire midgut epithelium. Electron microscopy revealed that electron- dense precursor material (possibly chitin) was present, bathing the mi crovilli during the first 12 h after blood feeding. This secretion app eared to originate from the bases of the microvilli. From 1 to 36 h, a n electron-lucid precursor material (possibly protein) was secreted fr om the entire length of microvilli and from their bases. Both precurso rs appeared to be formed at the epithelial surface, not associated wit h secretory vesicles. The envelope developed rapidly from precursor ma terial, and by 6 h a defined electron-lucid structure was present abov e the microvilli. Most mature envelopes (12-36 h) were 0.5-2.1 mu m th ick, multilayered, wholly electron-lucid, and composed of microfibrils and granules. Electron-dense components were seen in some envelopes a t 24-36 h. An anterior hyaline plug was present from 12 to 36 h. Envel opes were composed of chitin, protein, and glycoprotein, based on chem ical and histochemical tests. The likely presence of several amino aci ds (lysine, aspartic acid, and glutamic acid) that may cross-link chit in and protein was demonstrated by a positive ninhydrin-Schiff test. T his study constitutes the first ultrastructural investigation of perit rophic envelope development by a New World sand fly.