Toxicities of some heavy metals to the tadpoles of frog, Microhyla ornata (Dumeril & Bibron).

Static bioassays were conducted to determine the relative acute toxicities of five heavy metals (mercury, cadmium, copper, manganese and zinc) to 1-week-old and 4-week-old tadpoles of the frog, Microhyla ornata. Toxic effects were calculated on the basis of LC50 for 24 h, 48 h, 72 h and 96 h exposures at 25.5-26.0 degrees C. Mercury was the most toxic and zinc was the least toxic of the heavy metals tested. The sensitivity of the tadpoles to the heavy metals increased with increased age.