788 BLAYLOCK AND FRANK 



were confined in each compartment. Portions of the sides and 

 bottom of the containers were replaced with stainless-steel screen to 

 allow for water circulation. Each compartment had a screen cover to 

 keep the fish from swimming to the surface of the water. The 

 temperature of the test compartments was continually monitored. 

 Irradiated and control groups were alternated between test compart- 

 ments. Cessation of opercular movement was used as the biological 

 end point for survival. 



An analysis of variance test was used to compare the results for 

 each dose and time. Duncan's multiple range test was then used to 

 distinguish the significantly different (P < 0.05) results. 



Three Gambusia were taken from the 500- and 1500-rad dose 

 levels at days 5, 15, and 30 for pathological studies. They were fixed 

 in Bouin's fluid, and, after decalcification was completed, routine 

 histological techniques— embedding in paraffin, sectioning on a 

 rotary microtome at 5 ju, and staining with hematoxylin and 

 eosin— were used to prepare the tissue for microscopy. 



RESULTS 



The results of the CTM type tests for irradiated Gambusia are 

 shown in Table 1. Only at 1500 rads and day 15 was the value 

 significantly different from the controls (P < 0.05). The greatest 

 range of individual CTM values (38.1 to 40.6°C) was also found at 

 this dose and time. The CTM values were very consistent, with a 

 majority of the fish having CTMs of 40°C or above, except for those 

 irradiated at 1500 rads at day 15. For this treatment 7 of the 10 fish 

 had CTM values of less than 40° C. 



TABLE 1 



LETHAL TEMPERATURES (°C) FOR Gambusia affinis AFTER 

 ACUTE DOSES OF IONIZING RADIATION 



*Values in parentheses are standard errors. 



tThis CTM differed significantly (P < 0.05) from the others. 



