The ultrastructure of the adult stage ofTrichostrongylus colubriformisandHaemonchus placei

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Abstract
The ultrastructure of the adult stage of T. colubriformis and H. placei was studied. The cuticle of both nematodes was composed of (1) a membrane-bound layer, (2) external cortex, (3) inner cortex, (4) matrix, (5)–(7) three fibre layers, and (8) a basal lamella. Pear-shaped bodies embedded in the matrix layer in H. placei occur, along the length of the animal, once per annulus. A thin hypodermis enlarged to form lateral, dorsal and ventral cords which contained hypodermal cells, nerves and excretory canals. The muscle cells were large and multilobular. Two sizes of myofilaments, present in the contractile part of the cell, conformed to the filament arrangement of obliquely striated muscle. The mouth, buccal cavity and oesophagus of the alimentary tract were lined with cuticle. The oesophagus contained gland cells, muscle cells and apical cells. The lumen of the intestinal cells of both species had a well-developed microvillar border. In H. placei each microvillus was encircled by a ring of apparently spirally orientated vesicles or tubules.The authors are grateful to Dr D. W. Brocklesby for his help and advice. They would also like to thank Dr D. L. Lee and Dr W. G. MacMillan for helpful discussions.