ULTRASTRUCTURAL COMPARISON OF EXTRACELLULAR AND INTRACELLULAR ENCAPSULATION OF BRUGIA-MALAYI IN ANOPHELES-QUADRIMACULATUS

Ultrastructural aspects of extracellular humoral encapsulation of micr ofilariae of Brugia malayi in the hemocoel of Anopheles quadrimaculatu s were compared with those of intracellular encapsulation of first-sta ge larvae (L,) of the same parasite species, in the thoracic muscle ce lls of the same species of mosquito. The results showed that extracell ular humoral encapsulation of microfilarial sheaths, and sheathed and exsheathed microfilariae, in the hemocoel of mosquitoes occurs around the parasite within the first 6 hr postingestion, apparently without i nitial participation of hemocytes. Hemocytes and their remnants were o bserved near the parasite during the first 6 hr postingestion. Within the next 24 hr, hemocytes attach to the initial humoral capsule. By co ntrast, intracellular encapsulation of L(I)s is initiated by the accum ulation of dense cytoplasmic layer derived from the infected thoracic muscle cell. Melanin deposits accumulate in this layer adjacent to the parasite cuticle, again without visible participation of hemocytes.