Abstract
Scanning electron microscopic observations have been made on the microfilariae of Brugia malayi and B. pahangi which already cast off their sheaths in vitro. The microfilariae of both species have striated appearances. B. malayi microfilaria varies in number of striations between 402 and 442 with an average of 423, and B. pahangi microfilaria between 443 and 485 with an average of 458. Except for the difference in number of striations, B. malayi presents close morphological resemblances to B. pahangi. The anterior end of the microfilaria forms the bluntly rounded cap provided with a wedgeshaped hook and two small pores. The hook measures 0.7-1.1 microns in length and projects backward. Of the two pores, one, rectangular in shape, exists at the center of the cephalic cap and the other, round in shape, lies between the base of the hook and the rectangular pore. Three fang-like spines are situated on the first annulus opposite to the hook side. The spines are equal in length, 0.6-0.7 micron, to one another. The spines usually point backwards, though they are occasionally directed forwards by the withdrawal of the cephalic cap into the cephalic space. The excretory pore lies on around the 150th annulus from the anterior end, but the opening of the anal pore has not been found in the present study. The tail tapers gradually showing striations, though near the end a few annuluses become expanded. The terminal appendage, connected to the last expanded annulus, is 6-7 microns long, club-shaped and striated.
