The Life History of Plagitura salamandra Holl, 1928 (Trematoda: Plagiorchiidae)

Abstract

This work was undertaken with the idea of throwing some light on the validity of the two species of Plagitura, P. salamandra Holl, 1928, and P. parva Stunkard, 1933, occurring in the intestine of the newt, Triturus viridescens. The genus, Plagitura, was erected by Holl (1928) to contain a species of trematode found by him near Durham, North Carolina, and which he called Plagitura salamnandra. Stunkard (1933a, 1933b) reported on the morphology and preliminary work on the life cycle of a new species, Plagitura parva, collected from various points on the eastern coast of the United States. T. D. Brown in 1934 (unpublished thesis, University of Virginia) arrived at the same conclusion as Price (1930) had, viz., that P. salamandra Holl, 1928, was a synonym of Manodistomum occultum Stafford, 1905. Kelley (1934) recognized the validity of Plagitura salamandra and reported on the great variation in P. salamandra taken from newts collected from Massachusetts, Pennsylvania, Ohio, and Virginia. Stunkard (1936) reported the complete life cycle of P. parva and contended that by the recognition of two species the variations reported by Kelley could be explained. Furthermore, he recognized the validity of Manodistomum occultum and Plagitura salamandra. In his life history studies, Stunkard found that the eggs of P. parva were ingested by the snail, Helisoma anceps (Menke)= H. antrosa (Conrad) in sensu Stunkard (1936) where they hatched. The miracidia penetrate the gut wall and develop into sporocysts. There is a second generation of sporocysts which in turn produce cercariae. The cercariae are provided with stylets and proteolytic glands with which they penetrate several species of snails and aquatic insect larvae where they encyst as metacercariae. The final host, Triturus viridescens, becomes infected with the adults as a result of ingesting the encysted metacercariae. Stunkard (1936) reported that Helisoma anceps failed to become infected when fed eggs of Plagitura salamandra. The snail Pseudosuccinea columella (Say) is abundant in the vicinity of Charlottesville, Virginia. I. M. Schor in 1934 (unpublished thesis, University of Virginia) recorded many observations on the cercariae escaping from this snail as well as the fact that these cercariae would not encyst in tadpoles. When it was found that the cercaria from Pseudosuccinea columella was morphologically similar to the cercaria of Plagitura parva, as reported by Stunkard (1936), experiments were undertaken to see if the life cycle of this species could be experimentally worked out. A preliminary report of these experiments was made at the 1943 meeting of the Virginia Academy of Science (Owen, 1943).