Histochemistry ofHymenolepis microstoma(Cestoda: Hymenolepididae)

Abstract

Reduction of neotetrazolium in the presence of succinate is used as a quantitative assay for succinic dehydrogenase activity in homogenates ofHymenolepis microstoma, and nitro blue tetrazolium and thiazolyl blue tetrazolium-cobalt are employed with cryostat sections for its histochemical localization in adults and cysticercoids. The highest concentrations of the enzyme occur in the anterior region of the worm (scolex, neck, and immature proglottids), lesser amounts in the region of mature and early gravid segments, and least amounts in the gravid region of the strobila. Primary sites of succinic dehydrogenase activity are the mitochondrial layer of the cuticle and the cells of the subcuticle. In the anterior region the entire parenchyma shows uniformly high concentrations of enzyme activity. This reaction decreases posteriorly until, in the gravid region, only the subcuticle and the mitochondrial layer of the cuticle display activity. Intense activity was also noted in the layer just under the shells of the eggs. The ovary and immature testes show high enzyme concentrations; however, in the testes, the concentration diminishes as the organs mature. In the scolex, the rostellum and the muscles of the suckers show higher enzyme activity than the surrounding tissues. The scolex, inner membrane, and tail of the cysticercoid show uniformly high concentrations of formazan.