The effects of melanization on nutrient uptake by the microfilariae of Brugia pahangi were investigated by using in vitro melanization and autoradiographic techniques. It was found that the melanotic capsules which formed around the microfilariae in vitro completely inhibited the uptake of the following radiolabeled nutrients into microfilarial tissues: D-[6-H-3]glucose, L-[4,5-H-3]leucine, [2-H-3]glycine, [1-C-14]linoleic acid, [5,6,8,9,11,12,14,15-H-3]arachidonic acid, [2,8-H-3]adenine, [8-C-14]guanine HCl, and [5,6-H-3]uracil. These results provide strong evidence that melanization may kill the microfilariae by starvation. (C) 1995 Academic Press, Inc.