Ammonia and urea excretion in three species of air-breathing fish subjected to aerial exposure
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Proportions and rates of excretion of ammonia and urea and their levels in blood and liver were determined in two obligate (Anabas scandens andChanna gachua) and one facultative (Mystus vittatus) air-breathing teleosts.A. Scandens andC. Gachua, when exposed to air and returned to water, showed marked increase in the proportions of excretion of ammonia N and urea N, the increase in the rate of excretion of urea N being much greater. Significantly high urea N levels in blood and liver were noticed in both species following emersion. Extra synthesis of urea and marked shift towards ureotelism seem probable in exposedA. Scandens andC. Gachua. No such adaptive shift was observed inM. Vittatus. Ability to survive for longer periods out of water byA scandens andC. Gachua may be attributed to this adaptive shift besides other physiological adaptations.
KeywordsAnabas scandens Channa gachua Mystus vittatus ammoniotelism ureotelism
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