Oxidative enzymes in the development of Fasciola hepatica L. II. Dehydrogenase activity of miracidium

Histochemical methods were used to detect succinate, isocitrate, malate, lactate, alpha-glycerol phosphate' L-glutamate, alcohol, glucose-6-phosphate, 6-phosphogluconate, and beta-hydroxybutyrate dehydrogenases in miracidium--a free living larva of Fasciola hepatica. Examinations were carried out on miracidia which had just left egg covers and on those which had survived for 18 and 24 hours, respectively. Differences were observed regarding the occurrence and intensity of the enzyme activity depending on the age of the larvae. On the basis of the localization of dehydrogenases and persistence of their activity in the miracidia in various periods of their lives, the author concludes that in young larvae there exist three parallel modes of oxidation: glycolytic, in the tricarboxylic acid cycle, and in the pentose cycle. Moreover, there occur processes of amino acid metabolism and of fatty acid oxidation. The 18-hour larvae exhibit a marked predominance of oxidation in the Krebs cycle, the remaining modes being less pronounced, and after 24 hours the only way to obtain energy in the miracidium is oxidation in the Krebs cycle. Likewise noteworthy is the enhancement of the processes of fatty acid oxidation, this being evidenced by an intensified activity of beta-hydroxybutyrate dehydrogenase. The role of each enzyme in the metabolism of the larva is discussed.