Electron microscope study on the developmental stages of Wuchereria bancrofti in the intermediate host: structure of...

The cuticle, hypodermis and musculature of first, second and third stage larvae of Wuchereria bancrofti from the mosquito vector were studied by transmission electron microscopy. The young first stage larva is characterized by a thick cuticle with distinct layers demonstrating oriented fibrils. The muscle cells are well developed while the hypodermis has undifferentiated cytoplasm. - The late first stage larva (sausage-stage) still has a thick cuticle but the fibrils are no longer discernible. The volume of the hypodermal cells increases considerably, their plasma shows an abundance of organelles. The muscle sectors are shifted apart from each other by the growth of the hypodermis. The muscle cells are small, they start to multiply. - The cuticle of the second stage larva consists of three thin laminae only. The number of the hypodermal cells increases. They form the characteristic hypodermal chords. The four muscle sectors contain poorly developed muscle cells which multiply until the onset of the second moult. - The third stage larva shows a thick, multilayered cuticle with fibrous sublayers. Hypodermis and musculature are well differentiated. The hypodermal chords protrude into the centre of the worm. The muscle cells have grown considerably and their outer fibrillar portions show beginning septation.