Studies on the excretory “bladder” and caudal ducts of the supposed anepitheliocystid cercariae of Schistosoma mansoni

Summary

Optical and electron microscope studies of the supposed anepitheliocystid cercariae of Schistosoma mansoni indicated that the only bladder-like structure was the excretory atrium. No bladder was found anterior to it. The wall of the atrium was lined with tegument which was continuous with that of the outside. Thus the entire structure had a protoplasmic lining. There were two caudal ducts exiting the atrium which joined posteriorly and continued down the length of the tail. The caudal duct bifurcated at the posterior end of the tail, traversed the length of each furca, emptied into a chamber near the tip of each furca, and finally exited through the excretory pore at the very tip of each furca. The caudal and furcal ducts were entirely intracellular. No lateral excretory pores at the tail-body junction were noted, nor was there a retrogression of the caudal ducts. An Island of Cort was present.

The findings of this study cast more doubt upon the research and criteria that were used by La Rue (1957) in establishing the superorders Anepitheliocystidia and Epitheliocystidia. Until further research comes forth to support these groups, they should be considered invalid.