The Microfilaria of Brugia: A First Stage Nematode Larva

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Abstract
(1) The structure of the microfilaria of Brugia (B. patei and B. pahangi) is redescribed and the development of B. patei is followed in the mosquito Aedes togoi for the first 4 days, up to the moult to the second larval stage.(2) The buccal cavity, the pharynx (or oesophagus), and the pharyngo-intestinal valve of the second stage larva are formed around the pharyngeal thread of the microfilaria. Part of this thread is moulted with the microfilarial cuticle at the moult to the second larval stage.(3) The intestine of the second stage larva is built up around the Innenkörper of the microfilaria from cells of the nuclear column.(4) The R cells (G 2—G 4 cells) of the microfilaria and the anal vesicle of the microfilaria continue into the second stage larva and eventually the rectum is formed between them.(5) The G cell (G 1 cell) does not form part of the gut of the second stage larva but becomes incorporated into the body wall with other cells from the nuclear column.(6) The subcuticular cells of the microfilaria continue as elongate spindle shaped cells in the cords of the second stage larva.(7) The significance of these results, which are at variance with earlier descriptions, are discussed and it is concluded that the microfilaria of Brugia is a very much modified first stage nematode larva, adapted to life in the capillaries of the vertebrate host. The microfilaria begins the metamorphosis to the structure of the second larval stage soon after entry into the insect vector.