Aspects of the Larval Development of Ophthalmophagus sp. (Trematoda: Cyclocoelidae)

Abstract

Specimens of Ophthalmophagus (near) singularis were collected from the nasal cavities and orbits of clapper rails (Rallus longirostris) from Mississippi tidal marshes. The miracidia hatched in utero, emerged, and attached to marine snails (Melampus bidentatus and Detracia floridanus). The rediae of the miracidia bored into the snails, leaving the empty miracidia behind. By 3 weeks postexposure the rediae contained metacercariae. This is the first report on the life history of cyclocoelids in the genus Ophthalmophagus and the first demonstration of cyclocoelids parasitizing marine snails. Cyclocoelid life histories have been discussed by Taft (1973, 1975). Cyclocoelid larval development is condensed. Each miracidium contains a fully formed redia. After attachment to a snail by the miracidium, the redia penetrates. Within the pulmonate host, rediae will produce cercariae that either encyst within rediae producing them or in snail tissue. Birds ingesting gastropods with mature metacercariae become infected. The present study constitutes the first report of a life history in the genus Ophthalmophagus (Stossich 1902) and is the first record of cyclocoelids parasitizing marine snails. MATERIALS AND METHODS Gravid Ophthalmophagus (near) singularis (Stossich 1902) were collected from the nasal cavities and orbits of clapper rails (Rallus longirostris). Worms placed in dilute (10-15 %o) sea water released miracidia to which wild Littorina irrorata, Melampus bidentatus, and Detracia floridanus were exposed. Sora rails (Porzana carolina) and Virginia rails (Rallus limnicola) were additional sources of miracidia for infecting M. bidentatus. After exposure, snails were placed in plastic gallon jars containing dried marine emergent vegetation and approximately 3 cm of sea water, the level of which was maintained by adding distilled water. Snails were examined weekly and larval development noted. Infected snails or isolated rediae were fixed for sectioning in Bouin's or Zenker's solution and stained with Heidenhain's iron hematoxylin or Mallory's triple stain. Adult trematodes were fixed in AFA, stained with paracarmine and counterstained with fast green. Fifteen whole mounts and one secReceived for publication 4 October 1977. * Department of Biology and Museum of Natural History, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin 54481. t Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564. + Present address: Dauphin Island Sea Lab., P.O. Box 386, Dauphin Island, Alabama 36528. tioned specimen (stained with Harris' hematoxylin) from an earlier study (Heard, 1970) also were examined and measured. All molluscs and rails were collected from tidal marshes in Jackson County, Mississippi. Measurements are in micro-