Respiratory Functions of Body Fluids 



319 



distribution of fish. However, in goldfish the effect of COj on Oj utilization 

 decreases with rising temperature.''"' 



lOOr-^i — r 



lo 2o 3o Ao 



TEMPERATURE "C 



5o 



Fig. 74. Effects of temperature on the O2 tension for half saturation of blood of lower 

 vertebrates. • frog, Macela and Seliskar"'; O skate, Dill et al.'^; X brook trout, A rain- 

 bow trout, •) brown trout, Irving, Black, and Safford*^; =: eel, Kawamoto."* 



It has been mentioned previously (Ch. 8) that during periods when the 

 oxygen supply is low some fish may draw on the oxygen in their swim bladders. 

 The oxygen content of swim bladders in physoclystous fish— those with closed 

 bladders, such as sunfish, perch, bass and stickleback— is often higher than 

 that of air.^*'"'' ^^^ The amount of o!xygen secreted into the bladder is related 

 to the CO2 effect on ffee dissociation of iish hemoglobin. When CO2 increases 



