On the morphology of Heligmosomoides polygyrus (Nematoda-Trichostrongylidae) from the field mouse apodemus sylvaticus.

The morphology of the trichostrongylid nematode Heligmosomoides polygyrus is described by light and scanning electron microscopy. In light microscope, the present material agrees with the original description given by Baylis (1926), except for the addition of more details about the structure of the genital cone and the synlophe. The scanning electron microscopy of the present nematode revealed that the oral opening of the immature worm (L5) is rounded and its cuticular surface is loosely attached to the body, while the oral opening of the mature worm is triangular, the two copulatory spicules of the male are alate and closely adhering to each other and the right lobe of the male bursa is longer than the left one. Male prebursal and bursal papillae are described. The female posterior extremity is characterized by crescent vulval and anal openings and a terminal spike.