460 



BRADLEY 



TABLE 3 



ACCLIMATION OF Eurytemora af finis TO HIGH AND LOW 



TEMPERATURES, EXPRESSED AS VARIANCES 



AMONG EXPOSURE TEMPERATURES* 



B. Cold Tolerance 



Exposure time, days 



2.5 



Variance 



Female 



Male 



Female Male 



4and 10+ 15°C (a?) 42.0 7.1 124.2 



lOand 15°C(al) 12.0 2.8 



Overall (a|) 25.8 10.6 82.1 



Total variancef 95.8 102.6 233.6 



69.1 

 



41.8 



173.6 



*Method 3, Appendix B. 



fTotal variance was calculated as o\ + 0%] . 



ments where there was a delay of 1 day in measuring for heat or cold 

 tolerance, the correlations were always around zero. Hence, the 

 earlier positive correlations between heat and cold tolerances may be 

 artifacts of retesting animals within a few hours instead of allowing 

 them a day to recover. In no case was there any detectable effect of 

 testing for heat or cold tolerance first. The conclusion must be that 

 heat and cold tolerances are not negatively related and may not be 

 related at all. Hence, I assume that adaptation to heat stress will not 

 necessarily compromise adaptation to cold stress, but I do not know 

 whether the genetic correlation (the proportion of genes affecting 

 both ch£iracteristics) is positive, negative, or zero. 



This discussion has been focused on temperature tolerance in 

 terms of individual resistance to temperature stress, in particular heat 

 stress. To mean anything to the species, consideration of temperature 

 tolerance should also include reproductive success. As a test of the 



