ULTRASTRUCTURE OF THE INTRACELLULAR MELANIZATION OF BRUGIA-MALAYI (BUCKLEY) (NEMATODA, FILARIOIDEA) IN THE THORACIC MUSCLES OF ANOPHELES-QUADRIMACULATUS (SAY) (DIPTERA, CULICIDAE)

Ultrastructural details of the melanization of the filarial parasite B rugia malayi (Nematoda: Filarioidea) in the thoracic muscle cell of se lected susceptible and refractory strains of Anopheles quadrimaculatus (Diptera: Culicidae) were examined. In both susceptible and refractor y strains, following infection of the muscle cells, there is a dissoll ution of the sarcoplasmic cytoskeletal matrix surrounding the myofibri ls, causing the myofibrils and mitochondria to drift apart and lose th eir regular spacing. This is coupled with a reorganization of the cyto plasm near the normally developing intracellular accumulate near the l arva. Eventually, these form a dense layer of cytoplasm around the par asite. Fine grains of melanin begin to appear in this dense cytoplasmi c layer, increasing gradually until a nearly complete capsule of melan in surrounds the larva. The time course of melanization was found to b e quite variable among and even within mosquitoes. Strains of A. quadr imaculatus selected to be refractory or susceptible to B. malayi, were found to vary substantially in the frequency of intracellular melaniz ation, but not in the mechanism.