Preliminary results on the ichthyocidal properties of <i>Euphorbia ingens</i> (Euphorbiaceae)

Abstract

Euphorbia ingens belongs to the family Euphorbiaceae, which includes a variety of latex-producing plants, the majority of them having ichthyocidal properties (Coates-Palgrave 2000). Tests to determine the degree of virulence of E. ingens latex used Cyprinus carpio and Xenopus laevis as the main test organisms. Fish and frogs were exposed to various concentrations of latex to determine the concentration lethal only to the fish. The same concentrations were then used to determine the stability of the latex, by exposing fish in tanks with and without biological filtration. The breakdown period varied, with it breaking down quicker with biological filtration than without it. Once the stability of the latex within a system was determined, crabs, aquatic snails, frogs and fish were all simultaneously tested in a tank at the same concentration as before. Within 12 hours all the fish and half the frogs died, whereas the crabs and snails appeared not to suffer any detrimental effects. The poison degraded and became harmless to fish within 48 hours. Thus, the latex of Euphorbia ingens is a temporarily effective ichthyocide when applied in the correct concentrations.

African Journal of Aquatic Science 2004, 29(2): 265–269