Biological Effects of Ionizing Radiations on Protozoa: Some Discoveries and Unsolved Problems

Because of their universal occurrence in nature, the ease with which they may be collected and cultivated, and the manner in which they lend themselves to experimentation, protozoa have proved to be invaluable in the study of biological effects of ionizing radiations. It is of interest to note that one of the most eminent protozoologists, Fritz Schaudinn, was the first to report on the biological effects of X-irradiation on protozoa. His research was done in 1896- 1 year after Professor Rontgen dis-covered X-rays at Wurzburg. However, Schaudinn's work was not published until 1899. He reported (in translation) ".... I will impart my results because they may possibly induce someone to continue these experiments which for me are not possible at the present time. " Twenty one species were inves-tigated by him of which 12 were amoebae, four were sporozoans, four were flagellates, and one a ciliate. Although he admitted that his observa-tions were fragmentary, Schaudinn noted the existence of comparative differences in X-ray effects in behavior of locomotor organelles and in some physical and physiological changes in the protozoa as a result of the irradia-tion. Schaudinn's pioneering work is now largely of historical significance. Other earlier workers also simply expose