Stichosomes occur in two orders of the Nematoda: Trichinellida, with at least
six families, and Mermithida, with two families. Recent phylogenetic analysis
based on a synthesis of molecular and morphological data suggest that the
stichosome may be an example of parallel evolution in the Trichinellida and
Mermithida (De Ley and Blaxter, 2002; Ferris, 2007).
The pharynx is narrow and thin-walled anteriorly and which, posteriorly, is
surrounded by unicellular, glandular stichocytes, each with a duct into the
pharyngeal lumen.
The pharynx extends one-fourth to nine-tenths of the body length in various
taxa and is almost devoid of musculature. The region of the pharynx surrounded
by stichocytes is known as the stichosome.
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