Trematode Excretory Concretions: Formation and Fine Structure

Abstract

Staining and microchemical analysis indicate that trematode excretory concretions, as examplified by Acanthoparyphium spinulosum, are composed chiefly of calcium carbonate and a trace of phosphate. The calcium salts are delivered to the main collecting vessels in a fluocculent state. Mitochondrial and cytoplasmic membranes are released from cells of the collecting vessel wall into the lumen of the vessel. Mitochondria and possibly cytoplasmic membranes are modified to form centers or nuclei around which the calcium salts are deposited in concentric layers. The layering begins peripherally with the layers encompassing the entire concretion and secondarily material becomes layered around the nuclei. The electron microscope has been used to study the the fine structure of the concretions. The concretion material may be useful to the trematode in the fixation of carbon dioxide and in the buffering of acids.