PARENT SESSION
TP7 The use of biomarkers for assessing ecosystem damage
3:00 PM to 6:30 PM, Tuesday, 08 May 2001
Session Chair: L. Guilhermino
Room 7

(269) Effects of pesticides on detoxication enzymes in tadpoles of sensitive species of amphibians.

Pflugmacher, Stephan¹, Greulich, Kerstin¹, ¹

ABSTRACT- Populations of many amphibian species all over the world appear to undergone declines and range reductions in recent time. Amphibian populations are potentially sensitive to aquatic contaminants like acid deposition, nitrogen fertilizers and also pesticides and may therefore be possible causes for the decline of amphibians. In the present investigation spawn and tadpoles of amphibians - yellow-bellied toad (Bombina variegata) and fire-bellied toad (Bombina bombina) - were exposed to the phenyl-urea herbicide isoproturon. Physical and behavioural abnormities already developed at concentrations as low as 0.1 g/l in 24 h exposure. In addition to the reduced mobility (lateral swimming), developmental deformities including bent tails, body swelling and bulging, head deformities and digestive-system deformities occured. The results of the exposure with 1 g/l ¹⁴C-labelled isoproturon indicate the uptake into the larvae. After 48 h 4.3% of the used radioactive amount were found in the tadpoles. Furthermore the contamination of spawn was investigated. In the chorion as well as in the embryo of Bombina variegata and Bombina bombina detection of ¹⁴C-residues was possible. Obviously the chorion can not preserve the embryo from the uptake and influence of isoproturon. In vivo metabolism of ¹⁴C-labelled isoproturon was investigated in Bombina variegata tadpoles after 48 h exposure time. Whole body extracts were detected by HPLC for any of the known IPU-metabolites. In larvae of the yellow-bellied toad the detoxication of isoproturon was investigated, by measuring the activity of microsomal and soluble gluththion S-transferase. This phase II enzyme system could be used as an excellent biomarker to describe the enzymatic response of the contamination with isoproturon. Activities of the soluble gluthathion S-transferase increased in time- and dose-dependent manner corresponding to elevated stress.

Key words: amphibian, isoproturon, detoxication enzymes, metabolism