Comparative Fine Structure of the Esophagus of Males of Heterodera Glycines and Meloidogyne Incognita 1)

The fine structure of the esophagus, including procorpus, metacorpus, isthmus, gland lobe, and esophago-intestinal junction is compared in males of Heterodera glycines and Meloidogyne incognita. Although the anterior portion of the esophagus is similar, striking differences are observed posterior to the metacorpus. In both species the esophageal lumen is lined with cuticle consisting of four layers. The lumen is round in the procorpus, and triradiate from the metacorpus valve (pump chamber) through the isthmus. In M. incognita the lumen terminates as a network of membranes between esophago-intestinal cells. These cells are excluded from the anterior portion of the glandular isthmus at about 10 μm posterior of the metacorpus valve. In H. glycines the lumen extends the length of the isthmus, and terminates in similar membranes near the level of the dorsal gland nucleus. In M. incognita, the intestine extends anteriorly from the esophago-intestinal cells and forms a distinct intestinal caecum. The gland lobe of H. glycines consists of a dorsal gland with a process which terminates anteriorly in the procorpus, and two indistinctly separated subventral glands with processes which terminate in the subventral sectors of the metacorpus. The gland lobe of M. incognita consists solely of two subventral glands, one of which is longer, and posteriorly is composed of a distinct cortex, medulla and core. Each gland has a subventral process, which terminates anteriorly in the metacorpus. Although a vestige of a dorsal gland process is present in the anterior part of the procorpus, a dorsal gland was not observed in males of M. incognita. The esophagus of both species is innervated by nerve processes which originate from ganglia associated with the nerve ring as well as from perikaryons within the metacorpus. Muscular elements are limited to radial muscles in the metacorpus, and sheath muscles near the junction of metacorpus with isthmus.