Chrysonema aurum, Thorne, Gerald, 1929

Thorne, Gerald, 1929, Nematodes from the Summit of Long's Peak, Colorado, Transactions of the American Microscopical Society 48 (2), pp. 181-181 : 189-190

Chrysonema aurum n. g., n. sp.

Diagnosis:

Characters of Dorylaimus with these differences: Labial papillae absent, their place being taken by a circular ring about the entrance to the pharynx. Vulva at 34%; ovaries two; vagina heavily cutinized the entire length, the cutinized walls being hemispherical in appearance from a lateral view. Tail ventrally bent, ending in a sharp, hooked terminus.

This exceeding beautiful nema owes its name to the brilliant golden color of the contents of the intestine. Usually only the portion posterior to the vulva is colored but occasionally it extends forward almost to the esophagus.

The slender body is widest at the vulva. Anteriorly it tapers uniformly to the lip region which is two-fifths as wide as the body width at the vulva and half as wide as the neck at the base of the esophagus. Posteriorly it tapers with a like uniformity to a point near the beginning of the prerectum where it becomes more conoid and ends in an acute, ventrally bent, hooked terminus. The cuticle is marked by excessively fine striae that usually are visible only on the anterior portion of the body. On favorable specimens these striae can sometimes be resolved into rows of exceedingly minute dots.

The hexagonal lip region bears a single circlet of innervated papillae on the outer margin but they do not interfere with the contour of the head.

The amphid openings are obscure, slit-like markings about one-fourth as wide as the head and from them the inner connections can easily be traced back to fusiform sensilla pouches located somewhat back of the base of the spear. About the mouth is a ridge set off by a circular furrow in the face. In the center of this circular area is the slightly depressed entrance to the narrow, tubular vestibule. The double guiding ring of the spear is of exceedingly delicate construction. The dorylaimoid spear is slightly longer than the width of the lip region and uniform in width in the posterior two-thirds, the anterior third tapering to a very sharp point. The anterior portion of the typically dorylaimoid esophagus is but one-fourth as wide as the posterior portion, the esophagus being enlarged at its middle by a rather sudden expansion. The indistinct nerve ring crosses the esophagus rather squarely and its location is marked by somewhat refractive bodies, apparently six in number. The lumen of the esophagus is unusually narrow. The cardia is elongate-hemispherical in form and one-third as wide as the body. The thin walls of the intestine are made up of large cells in which the granules are fine and scattered. The prerectum is one to two times as long as the rectum and is slightly narrower than the adjoining portion of the intestine. The straight rectum is as long as the anal body-diameter. From the depressedvulva the cutinized vagina leads one-third the distance across the body, its walls being hemispherical. The front ovary is on the right, the rear on the left, side of the body and they are reflexed almost to the vulva. When crowded by the eggs, which are four times as long as the body width, they sometimes extend past the vulva or are folded again. No phasmids or deirids have been seen. Males unknown. Fig. 10a-e.

Only one specimen in this collection but many others have been secured from soil collected in fields, deserts and mountains of Utah, Colorado and California. Three specimens found the surface of “ Mormon Crickets. ” on Anabrus simplex , secured on Diamond Mountain, Uintah County, Utah. It may inhabit the bodies of other insects which might account for its wide distribution from sea level on the Pacific Coast to the top of Longs Peak, Colorado.

Figures

Chrysonema aurum n. g. , n. sp.

Fig. 10a-e.