PROSSER 



ones, the two curves may intersect by extrapolation above the normal 



temperature range (Figure 4d). Examples for vertebrates are heart 



rate of the newt Triton (Mellanby, 1940), metabolism of cottid fish, 



winter and summer, northern and southern latitudes (Morris, 1961) , 



o o 



and O consumption by frogs acclimated to 5 C and 25 C (Riech et 



al., 1960). If the Q of cold- acclimated animals is higher (Figure 

 4e), the two curves may intersect at alow temperature, often by ex- 

 trapolation. Above the intersection the rate is greater for cold- ac- 

 climated than for warm-acclimated animals. This is reported for 



o o 



O consumption by the crucian carp acclimated to 5 C and 26 C 



(Suhrman, 1955) and for O consumption by brain tissue of goldfish 

 (Freeman, 1950). 



Translation of a rate-temperature curve implies a change in ac- 

 tivity (in a thermodynamic sense) and may be caused by change in 

 enzyme concentration, change in the relative activities of enzymes in 



series or in parallel, or a change in controlling conditions ionic 



strength, pH etc. Rotation of a rate- temperature curve implies a 

 change in Q and hence in activation energy and may result from 

 alteration of me enzymatic protein, change in some co- factor, or a 

 shift in control of a reaction to alternate enzymatic pathways. Differ- 

 ent tissues of the same animal may show different patterns of meta- 

 bolic acclimation, e. g., the heart of goldfish shows no change, but 

 skeletal muscle, and to a lesser degree liver, shows acclimation 

 with a reduction of Q in the cold. 



Metabolic and Enzymatic Changes 



A number of selected examples of compensatory acclimation of 

 metabolism of intact poikilo thermic vertebrates is given in Table I. 

 A greater oxygenconsumptionof cold- than of warm- acclimated ani- 

 mals when measured at intermediate temperatures is indicated for 

 lampreys (Scherbakov, 1937), eels (Precht, 1951), marine fish Fun- 

 dulus and Gellichthys (Wells, 1935a,b), goldfish for both active and 

 standard metabolism (Kanungo and Prosser, 1959a) , and frogs (Riech 

 1960). The extent to which photoperiod and nutritional state modify 

 these differences is not clear, but the principal experimental vari- 

 able in each experimentwas temperature. When measured at the ac- 

 climation temperatures, the maximum active metabolism is lower 

 than the maximum standard metabolism (Fry and Hart, 1948b); if 



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