Formation of calcareous corpuscles in the lumen of excretory canals of Taenia solium cysticerci

Platyhelminths, like many other organisms, are capable of producing mineral concretions. In cestodes these are referred to as calcareous corpuscles. S tudies on these concretions in different cestodes both in vivo and in vitro have resulted in a number of hypotheses on their origin, formation, and st ructure. Calcareous corpuscles are believed to be of cellular origin, altho ugh the kind of cell involved and the mechanisms of mineralization remain u nder discussion. In the present paper we show that formation of calcareous corpuscles in cysticerci of Taenia solium is not of intracellular origin, a s described for other cestodes, but occurs extracellularly in the lumen of protonephridial ducts in a way similar to that proposed for trematodes. Thi s finding enhances the function of the protonephridial ducts, at least in t he larvae of T. solium, to the roles formerly ascribed to the calcareous co rpuscles.