Stereo and scanning electron microscopic studies of the third stage larvae of Anisakis simplex.

Abstract

This study was to demonstrate the surface anatomy of the third stage larvae of Anisakis simplex in marine fish using stereo and scanning electron microscopes (SEM). The round worm is slender, elongated and of cylindrically shaped. The head of this worm is a globular structure. The mouth is triangularly shaped and surrounded by three lips. A boring tooth projects dorsally at the anterior end. There are four pairs of tactoreceptors, the labial papillae, enclosing the lips. The tail end is blunt and acquires a distinct slender process, the mucron. Stereomicroscopy revealed the esophagus is elongated, bulbous and club shaped, subdivided into an anterior muscular part and a posterior glandular part or ventriculus. The intestine is a long straight tube where the digestion and absorption occur. Waste pass through the intestine and is stored in the rectum until excreted via the anus. A SEM is a powerful tool in distinguishing worm species, as was seen when examining that the mouth of Anisakis simplex, which is triangular shaped and enclosed by three lips with one boring tooth; other species are different. The mucron projection at the distal end is another distinctive structure revealed by SEM.