The life-cycle of Echinoparyphium serratum sp.nov. (Digenea: Echinostomatidae)

Abstract

Echinoparyphium serratum sp.nov., with 37 collar spines, is described from experimentally infected ducklings and chickens. It appears to be most closely related to E. aconiatum but differs from it in having smaller eggs, fewer tegument spines, almost confluent vitellaria in the post-testicular region, and the inner margin of the ventral sucker is serrated. The natural host is unknown but thought to be a bird.Bile composition may account for the markedly different recovery percentages of adult worms from the two experimental hosts.Miracidia hatch between 9 and 11 days at 22 °C. Experimental infections of snails with miracidia have not been obtained.Rediae occur naturally in Isidorella brazieri Smith, and free-swimming cercariae encyst in the pericardium of the same species of snail.This latter part of the life-cycle is based on strong circumstantial evidence. A few cysts were occasionally found in the pericardium of Lenameria sp. but the enclosed metacercariae were dead.The cercaria can be distinguished from Cercaria echinata, the cercaria of E. aconiatum, and C. equispinosa in having cystogenous gland cells containing granular material only, and the inner margin of the ventral sucker serrated.I would like to record my sincere thanks to Professor J. D. Smyth for his advice, and comments on the manuscript.