Exhausting exercise in the hagfish, Eptatretus cirrhatus: The anaerobic potential and the appearance of lactic acid in the blood

1. 1. Hagfish ( Eptatretus cirrhatus) were able to sustain 30 min of forced swimming at ca 0.5 body lengths/sec without accumulating lactic acid in their tissues. 2. 2. When forced into extended bouts of burst swimming the muscles produced lactic acid, which entered the blood and caused a marked acidaemia. 3. 3. Enzyme activities in the myotome indicated a limited capacity for both anaerobic glycolysis and aerobic ATP production. 4. 4. There was no evidence for a preferential accumulation of lactic acid in the blood of the subcutaneous sinus rather than the central circulation. 5. 5. The animal can restore its acid-base balance before lactate is metabolised .