Lethal Effects of the Insecticide DDVP on the Eggs and hatchlings of the Snake-head, Channa punctatus (Bl.)

Ophiocephliformes: Ophiocephalidae

Abstract

Abstract Laboratory bioassays were made at 66 to 75°F to determine the effects of the organophosphorus insecticide DDVP on the viability of the sanake-head spawn and hatchlings. Sixteen different concentrations ranging from 0.10 to 20 ppm were tested against duplicate samples of eggs placed in cylindrical glass jars holding 8 litres of unchlorinated water. The eggs hatched at all test concentrations. Hatching time increased with the increase of concentration. All eggs hatched at concentrations up to 1.0 ppm within a period of 12 hours. Within the same period, about 60% eggs hatched at 1.6 to 16 ppm, and 55% eggs hatched at 20 ppm; the remainders hatched within 24 hours. Yolk-sac absorption was normal at 0.10 ppm. The yolk absorption gradually decreased at 1.6 to 4 ppm, and totally stopped at 5 ppm or more. The hatchlings were many times more sensitive to DDVP than the eggs. The median survival time of hatchlings gradually decreased with the increase of concentration. The eggs and hatchlings survived well at 0.10 ppm DDVP.