Abstract
Studies of bimodal oxygen uptake in four species of murrels, genus Channa, at different periods of the 24 h day regime showed distinct circadian rhythm in their metabolism.The metabolism of the four species remained higher in the period extending from dusk (16: 00-18: 00) to dawn (04: 00-06: 00).C.marulius showed the highest 02 uptake (66.4±0.5ml O2 kg-1.h-1) duringmidnight (24: 00-02: 00) , C.striatus (78.7±18.6) and C.gachua (95.6±2.6) during early parts of the night (20: 00-22: 00) and C.punctatus (57.5±1.1) during dusk (16: 00-48: 00).Of the total oxygen uptake, C.marulius, C.striatus, C.gachua and C.punctatus extracted about 84.5%, 67.7%, 53.4% and 86.8% of oxygen through aerial routes respectively.In all the species the lowest or the second lowest rate of oxygen uptake was recorded at noon, and during this period gill breathing dominated over aerial breathing in C.striatus and C.gachua. The circadian rhythm of their oxygen uptake has been correlated with the diurnal fluctuation of metabolism of the swamp ecosystem.A general metabolic wheel hypothesis has been postulated.
