In vitro Transformation of Schistosoma japonicum Miracidia to Young Sporocysts in a Culture System for Egg Maturation

Abstract

were filled with numerous spherical granules. In live specimens the ceca extended to the posterior margin of the acetabulum, but in fixed worms to midway between the acetabulum and the posterior end of the metacercaria. The most prominent feature of these worms was the large Y-shaped excretory bladder which was filled with numerous hyaline granules in an opaque fluid matrix (Figs. 1, 2). The excretory bladder had a posterior, terminal excretory pore and arms branching just posterior to the acetabulum and terminating at the level of the pharynx. In specimens stained with Semicohn's acetocarmine, genital primordia were seen just dorsal to the branching excretory bladder. Infection of bivalves with metacercariae can cause deformations in the shell of the host and pearl formation (Johannessen, 1973, Sarsia 52: 117-122). Damage to the body wall of A. ornata, however, appeared to be limited to a small papilla surrounded by a concentric indentation caused by attachment of the metacercaria by the oral sucker. Such damage to the host may have s s erical granules. In been due to feeding activity of the metacercaria or caused solely by attachment of the worm. In the May 1983 collection, all 4 metacercariae had a faint red material in the ceca. Identification of the red material as host hemoglobin or myoglobin was attempted using a microspectrophotometer, but was unsuccessful because the sample was too dilute. Amphitrite ornata is a common terebellid polychaete of mudflats where it lives in a stable mucus-lined burrow. The body wall of such a polychaete is functionally similar (as a habitat for metacercariae) to the extrapallial space of bivalves. Both provide a stable habitat for metacercariae, a possible food source, and the potential for transmission to the definitive host, probably a shore bird. Specimens of this gymnophallid metacercaria have been deposited in the USNM Helminthological Collection, accession number 78177. The authors acknowledge the assistance of Dr. James M. Colacino with microspectrophotometry. e to f eding activity of the metacercaria