Alteration in the Respiratory Pathway of the Freshwater Fish Channa Punctatus Induced by Euphorbia Royleana Stem Bark Extract
The piscicidal activity of the diethyl ether extract of Euphorbia royleana stem bark has been well established, but its ultimate mode of action and short, as well as long-term, biochemical effects are not yet known. Exposure of fish for either 24 or 96 hours to sub-lethal doses (40% and 80% of LC50) of the diethyl ether extract of the stem bark, significantly (P<0.05) altered total protein, total free amino acids, nucleic acids, glycogen, pyruvate, and lactate levels, as well as protease, aminotransferase, phosphatases and cytochrome oxidase enzyme activity in liver and muscle tissue of the freshwater fish Channa punctatus. These alterations were significantly (P<0.05) time and dose dependent. Thus, the diethyl ether extract of E. royleana stem bark shifts the aerobic pathway of fish respiration towards the anaerobic segment and also suppresses ATP production. This toxic effect was reversible, and seven days after withdrawal, all biochemical parameters were back to normal. These results support the view that the diethyl ether extract of E. royleana stem bark can be used for controlling unwanted populations of the predatory fish C. punctatus from aquaculture ponds.