During gradual air exposure, Amia calva show no reduction in oxygen consumption, no increase in plasma urea levels or in urea excretion. Blood pH remains constant, and plasma total CO2, PCO 2, HCO3 -. total ammonia and NH3 concentrations all rise significantly. Exposure to 923 μmol/l NH4Cl does not elicit an increase in urea production or airbreathing. Aquatic hypoxia without access to air does not cause a reduction in aerobic metabolism, and moderate levels result in death. These results suggest that Amia are incapable of aestivation, due to an inability to detoxify ammonia to urea and reduce metabolism, and die following three to five days of air exposure.
KeywordsAmia calva aestivation ammonia urea hypoxia
Unable to display preview. Download preview PDF.
- Babikker, M.M. and El Hakeem, O. 1979. Changes in blood characteristics and constituents associated with aestivation in the African lungfish, Protopterus annectens. Zool. Anz. 202: 9–16.Google Scholar
- Boutilier, R.G., Heming, T.A. and Iwama, G.K. 1984. Physicochemical parameters for use in fish respiratory physiology. In Fish Physiology. Vol. 9. pp. 401–430. Edited by W.S. Hoar and D.J. Randall. Academic Press, New York.Google Scholar
- Cameron, J.N. and Heisler, N. 1983. Studies of ammonia in the rainbow trout: physico-chemical parameters, acid-base behaviour and respiratory clearance. J. Exp. Biol. 105: 107–125.Google Scholar
- Delaney, R.G., Lahiri, S. and Fishman, A.P. 1977. Aestivation of the African lungfish Protopterus aethiopicus: cardiovascular and respiratory functions. J. Exp. Biol. 61: 111–128.Google Scholar
- Loveridge, J.P. and Withers, P.C. 1981. Metabolism and water balance of active and cocooned african bullfrogs, Pyxicephalus adspersus. Physiol. Zool. 54: 203–214.Google Scholar
- Neill, W.T. 1950. An aestivating bowfin. Copiea 240.Google Scholar
- Pusey, B.J. 1986. The effect of starvation on oxygen consumption and nitrogen excretion in Lepidogalaxias salamandroides (Mees). J. Comp. Physiol. 156: 701–705.Google Scholar
- Seymour, R.S. 1973. Energy metabolism of dormant spadefoot toads (Scaphiopus). Copiea 3: 436–445.Google Scholar
- Smatresk, N. and Cameron, J.N. 1982. Respiration and acid-base physiology of the spotted gar, a bimodal breather. I. Normal values and the response to severe hypoxia. J. Exp. Biol. 96: 263–280.Google Scholar
- Smith, H.W. 1961. From Fish to Philosopher. Doubleday and Co., New York.Google Scholar
- Soivio, A., Westman, D.C. and Nyholm, K. 1972. Improved method of dorsal aorta catheterisation: haematological effects followed for three weeks in rainbow trout (Salmo gairdneri). Finn. Fish. Res. 1: 11–21.Google Scholar
- Wolf, K. 1963. Physiological salines for freshwater teleosts. Prog. Fish-Cult. 25: 135–140.Google Scholar
- Zar, J.H. 1984. Biostatistical Analysis (2nd ed.) Prentice-Hall Inc., New Jersey.Google Scholar