RESPIRATION 



57 



Effect of Temperature. In poikilotherms, oxygen consumption increases 

 with rise in temperature up to some critical value, beyond which deleterious 

 effects become evident and the rate falls off sharply (Figs. 4.10, 4.12). 

 Q l0 values of 2-3 are usual, but at low temperatures much greater values 

 may be encountered, reaching 10-1 1 between C C and 5 C in some species. 

 Some Q 10 values for oxygen consumption are given in Table 4.4. 



The relationship between temperature and metabolism is linked with 

 many other factors. Seasonal acclimatization takes place in certain animals. 

 It has been noted that smaller animals of a given species show greater 



12 



Circulation 

 established 



Hatching 

 begins 



\ 



Days 



8 



10 



12 



Fig. 4.9. Oxygen Consumption during Embryogenesis of the Killifish 

 Fundulus heteroclitus. (From Amberson and Armstrong, 1933.) 



responses to temperature changes than larger ones (beach flea Tulorchestia, 

 sand crab Emerita, killifish Fundulus). The interrelations between external 

 oxygen tension and oxygen consumption are also affected by external 

 temperature, since high temperatures raise the metabolic rate (26, 39, 41, 

 65, 142, 150, 162, 171). 



Temperature Acclimatization. Animals are capable of adjusting 

 themselves to altered environmental conditions, a process known as 

 acclimatization. Differences in the physiological responses of individuals 

 of the same species from different latitudes may be due to acclimatization 

 rather than to differences in hereditary constitution. Studies on tempera- 

 ture acclimatization have been carried out on diverse functions: survival 

 at extreme temperatures, rates of many activities, e.g. heart beat, ciliary 



