The distribution of exogenous C(14)-succinic acid by Clonorchis sinensis incubated in Tyrode medium was studied by using autoradiographic techniques. A comparison was made between macro and microautoradiographs of this worm showed that black grains derived from labeled substance were distinctly observed in parenchymal tissue, oral sucker, ventral sucker, ovary, testes, and uterine tubules with eggs. In pharynx and intestine, a low density was monitored while negligible activity was found in seminal receptacle and vitelline follicles. In studying the further details, microautoradiography was utilized. The most radioactive regions were the reticular tissue and subcuticular musculature of this fluke, closely compatible with the finding of macroautoradiography. Apparent black grains of radioactivity were also found in oral sucker, ventral sucker, pharynx, uterine tubules, eggs in uterus, and intestinal ceca. Structures showing the least radioactivity included ovary, seminal receptacle and vitelline folliciles.
