ULTRASTRUCTURE AND MICROANALYSES OF THE CALCAREOUS CORPUSCLES OF THE PROTOSCOLECES OF ECHINOCOCCUS-GRANULOSUS

The calcareous corpuscles of the protoscolex stage of Echinococcus gra nulosus are irregularly spherical or ovoid in shape and have a diamete r ranging between 2 and 16 mum. The central region of immature corpusc les is composed of an electron-lucent matrix containing granular depos its and, in more mature corpuscles, paired membrane lamellae. Energy-d ispersive X-ray microanalysis of sectioned immature corpuscles demonst rated calcium, magnesium and phosphorus, whilst a quantitative analysi s indicated the presence of calcium and magnesium at 142.7 and 41.3 mg /g dry weight, respectively, and inorganic phosphate at 18.0 mg/g. Ass uming that the anion is predominantly carbonate, the molar ratio of Ca :Mg:HpO42-:CO32- is 1:0.48:0.08:1.41. X-ray diffraction patterns obtai ned from preparations of whole corpuscles indicated a poorly crystalli ne material including the mineral calcite. X-ray absorption near-edge spectra of corpuscles, taken over the phosphorus K edge, resembled tho se of brushite (CaHPO4.2H2O) and suggest that the phosphate, within th e corpuscles, is present in an amorphous, hydrated form that could be readily solubilised and mobilised for the metabolic processes of the o rganism.