PROTOZOA AND INVERTEBRATE EGGS 



317 



rnation is somewhat more easily affected than is the mating reaction itself. 

 At nonlethal doses, recovery from these effects seems to be possible. 

 Paramecium calkinsi is affected by somewhat smaller doses than P. 

 bursaria. 



Sensitization to Heat. Bo vie and Klein (1919) first reported that para- 

 mecia could be made more sensitive to heat by exposure to ultraviolet. 

 Giese and his coworkers have made a detailed investigation of this phe- 

 nomenon. Giese and Grossman (1945a) may be consulted for reports of 

 work with other organisms. 



The time to death at a single lethal temperature, 42°C, was used as a 

 measure of the resistance to heat. The possibility that the minimum 

 lethal temperature was changed was not tested. Giese and Grossman 



IOOt 



80H 



>• 



o 



2 60- 



UJ 



o 



40- 



20- 



2400 2600 2800 



WAVE LENGTH, a 



3000 



3200 



A CILIARY reversal"! 



# IMMOBILIZATION J STARVED 



O IMMOBILIZATION- FED 



Fig. 8-7. Action spectra for immobilization and ciliary reversal in Parawectuw, from 

 Giese (1945a). 



(194oa) investigated the action spectrum for heat sensitization of Para- 

 mecium. They found that 2483 A, the shortest wave length used, was 

 much more effective than 2537 A or still longer wave lengths. There was 

 a small secondary peak at 2804 A. The dose to reduce the time to death 

 at 42°C to half its control value can be calculated to be about 400 ergs/mm- 

 for 2483 A and about 1800 ergs/mm^ for 2804 A. 



They also found that recovery from the effect occurred. For all wave 

 lengths other than 2654 A the course of recovery was much the same, and 

 it was complete in about 4 days. Animals exposed to 2654 A recovered 

 much more slowly and recovery was only about two-thirds complete by 4 

 days. Giese and Grossman suggest that this means that more than one 

 material is involved and that the slow recovery from 2654 A is due to a 

 larger component of effect on nu(;leoproteins than at the other wave 

 lengths. 



Giese and Grossman (1945b) have shown that visible light in conjunc- 

 tion with a photodynamic dye can increase the sensitivity of Paramecium 



