The ultrastructure of the cuticle of the nematode Syphacia obvelata (Rudolphi, 1802). II. Modifications of the cuticle in the head end

Abstract

The head region of the pinworm Syphacia obvelata (Rudolphi, 1802) has been examined to determine the nature of modification of the cuticle responsible for, or associated with, lips and buccal capsule, cephalic papillae and amphids, cephalic inflations, and cervical alae. The median zone of the cuticle was found to be the most modified and variation in the extent and distribution of striated material is compatible with its proposed structural role. The variations found are probably related to compensation for stresses that may develop in the cuticle during the complex movements of the head end. Lips are only inconspicuous expansions of the body wall cuticle, while esophageal cuticle is strikingly different in appearance. It is proposed to refer to all regions of the mouth cavity bounded by both the lips and esophagus as the buccal capsule while only the limited region bounded by body wall cuticle may be referred to as stoma. A mechanism involving three groups of intrahypodermal cytoskeletal filaments attached to the tips of somatic muscles, esophagus, and cuticle is proposed to move the lips.