Parasitology, Harold W. Manter Laboratory of


Date of this Version



Proceedings of the Helminthological Society of Washington, v. 46, no.1 (1979)


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The morphology of Parascaris equorum of horses was studied; light and scanning electron microscopy were used. Late fourth-stage larvae have narrow, rectangular lips bearing few, large . triangular, irregularly spaced denticles and the lips are not markedly set off from the body. The cuticle of the late fourth stage is completely transversely striated, with incomplete longitudinal ridges creating a brickwork pattern; longitudinal alae are present. Total body lengths of fourth-stage larvae range from 10 to 32 mm. A single molting fourth-stage male was found to be 33 mm long. Early fifthstage nematodes have wide, trilobate lips with a deep transverse groove on their medial surface; the lips bear many small regularly spaced denticles and are set off from the body by a deep postiabial constriction. The fifth-stage cuticle is finely striated, without markings; longitudinal alae are lacking. Early fifth stages are 33.3 to 85.0 mm long.

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