Formation and Excretion of Calcareous Bodies by the Metacestode (Tetrathyridium) of Mesocestoides vogae

Abstract

The function of calcareous bodies, commonly found in the parenchyma of cestodes and trematodes, is relatively poorly understood. The present histochemical ultrastructural study of the proliferative tetrathyridia of Mesocestoides vogae revealed that calcareous corpuscles begin to form as organic (lipid-protein) masses that coalesce in parenchymal (calcareogenic) cells. Concentric accretion of organic and inorganic crystalline material then leads to the formation of typical refractile calcareous bodies. The precise composition of such bodies, determined by x-ray diffraction, revealed that their major inorganic constituent is indeed calcium, with significant amounts of phosphorus, silicon, and zinc as well. Emission of calcareous bodies through the tegument was observed by scanning electron microscopy, explaining their accumulation in the intracapsular spaces around worms embedded in liver tissue of the host. Following their emission, the crystalline substance of corpuscles dissolves, leaving only nonrefractile, membrane-bound cytoplasmic debris. These observations do not preclude the possibility that calcareous bodies may play some role as buffers or reservoirs of inorganic ions. However, it is difficult to accept such a function for unencapsulated worms in the coelom or intestinal lumen; we suggest that excretion is a more likely role in such sites.

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

“…This observation is inconsistent with the intracellular place of formation for calcareous corpuscles reported in taeniid cestodes, i.e., in either mesenchymal (Chowdhury et al 1962) or parenchymal cells (Etges and Marinakis 1991) or in germinal and brood capsule cells (Ohnishi and Kutsumi 1991). The only exception thus for reported is the hymenolepidid Hymenolepis microstoma, in which formation of calcareous corpuscles has been proposed to occur in three dierent ways, including one inside the capillary dilations connected with the osmoregulatory canals (Chowdhury and de Rycke 1977).…”

Post-embryonic development and ultrastructural characteristics of the polycephalic larva of Taenia parva Baer, 1926 (Cyclophyllidea, Taeniidae)

“…Initially, they remain and grow in the cytoplasm of the "CC-forming cell" but, after reaching a certain size, they destroy the cells and remain as a large accumulation in the intercellular space of the parenchyma. The major inorganic components of calcareous corpuscles are calcium, magnesium, Post-embryonic development of Taenia parva carbonate and phosphorus, with small traces of other elements; these constituents can vary considerably in relation to metabolic conditions and cestode species (Etges and Marinakis 1991). Their role is still not entirely understood.…”

Separation of calcareous corpuscles from plerocercoids of Spirometra mansoni and their binding proteins

“…The process of calcareous corpuscle formation has been well de®ned into two types, occurring extracellularly in the lumen of protonephridial ducts (VargasParada et al 1999) or intracellularly in mesenchymal cells (Chowdhury et al 1962), parenchymal cells (Etges and Marinakis 1991), and germinal and brood-capsule cells (Ohnishi and Kutsumi 1991) or via cytoplasmic autophagy in parenchymal cells (McCullough and Fairweather 1987). Calcareous corpuscles consist of an organic matrix and inorganic components, mainly calcium, magnesium, and phosphorus (von Brand et al 1965(von Brand et al , 1969.…”