Ultrastructural Features of the Body Wall of the Helminth Heterakis dispar (Schrank, 1790) (Nematoda, Heterakidae)

The structure of the body wall of the nematode Heterakis dispar (Schrank, 1790) from the family Heterakidae was studied using light and electron microscopy methods and compared with other species of the same family. The cuticle of the adult nematode H. dispar consists of eight layers: (1) epicuticle; (2, 3) outer and inner cortical layers; (4, 5) outer and inner homogeneous layers; (6, 7) outer and inner fibrous layers; (8) basement membrane. The homogeneous layer of the cuticle in the lateral ridges in both male and female and near the bursa of the male is several times as thick as other parts of the helminth cuticle. Unlike other species of the family, males of H. dispar have three different forms of cuticular structure in different parts of the body. In the basal layer of the cuticle, sustaining structures consisting of dense fibrils and microtubules were found, which were not previously noted in other species of the family. In the hypodermis of the nematode, dorsal, ventral, and two lateral ridges are found, the lateral ridges being twice as large as the others. Ultrastructural features of the excretory channels and nerve cords located in the hypodermal ridges were also revealed. The nervous system of the helminth is orthogonal. The ventral nerve cord is wider than the dorsal one. The muscle layer is of the polymyar type; number of muscle cells arranged in groups varies from 17 to 26, depending on the sex and body part of the helminth.