CHAPTER 8 



The Effects of Radiation on Protozoa and the Eggs of 

 Invertebrates Other than Insects* 



R. F. Kimball 



Biology Division, Oak Ridge National Laboratory 

 Oak Ridge, Tennessee 



Introduction. Lethal effects: Kind of death — Sensitivity — Recovery — Substances 

 present in the medium during irradiation — Effect on the medium. Retardation of cell 

 division: Recovery — Sensitivity — Localization. Inherited effects. Miscellaneous effects: 

 Activation of eggs — Excystment of protozoa — Motility and behavior of protozoa — Sensiti- 

 zation to heat — Miscellaneous microscopically visible changes — -Various physiological, 

 biophysical, and biochemical effects. References. 



INTRODUCTION 



From the point of view of a biologist interested in the effects of radia- 

 tion there is a certain unity between investigations with protozoa and with 

 the eggs of marine invertebrates — in both instances, one is deahng with 

 single cells in liquid medium; in both, the methods employed have tended 

 to emphasize the cell as an individual rather than as a member of a popu- 

 lation. So, while the connection between investigations with the two 

 kinds of material has sometimes been slight, it seems proper to consider 

 them together. 



The review could have been organized in many ways. The actual 

 choice, a consideration of each kind of effect separately, declares the point 

 of view to be that of an experimental biologist rather than a biochemist or 

 biophysicist. It seems important to stress that such frequently employed 

 radiobiological criteria as death and division delay may not be the same 

 in all materials. Actual occurrence of death of cells may be observed, not 

 just the end result, such as failure to produce daughter cells in large num- 

 bers. Division delay may be examined in detail rather than as an over- 

 all effect on the number of cells or mitoses in a population. From such 

 studies, it is clear that a variety of phenomena are concerned. When 

 investigations on many organisms have been made, it may be possible to 

 recognize certain phenomena which are common to all. Until this is 



* Manuscript prepared and work at Oak Ridge performed under Contract No. 

 W-7405-eng-26 for the Atomic Energy Commission. 



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