The newt Triturus carnifex as a model for monitoring the ecotoxic impact of the fungicide thiophanate methyl: Adverse effects on the adrenal gland

Abstract

The aims of this study were to propose a bioindicator organism, the newt Triturus carnifex, for the assessment of toxicological impact of thiophanate methyl in the Campania region (Italy) and the possible adverse activity on the adrenal gland. In the acute toxicity study, experimental groups of T. carnifex were exposed to 2.40, 4.80, 9.60 and 19.20 μg/L tap water of thiophanate methyl for 2 days; the LD 50 was found to be 9.60 μg/L. To evaluate the effects on the adrenal gland, newts were exposed to a dose of 25% of the LD 50 2 days for 8 days. The ultrastructural features of the tissues as well as the serum levels of aldosterone, corticosterone, norepinephrine (NE) and epinephrine (E) were evaluated. The number of secretory vesicles in the chromaffin cells appeared significantly decreased, whereas NE and E serum levels appeared strongly increased. Moreover, corticosterone and aldosterone serum levels appeared significantly reduced. The results suggest that: 1) T. carnifex has the features of an ideal bioindicator, due to its high sensitivity to thiophanate methyl, 2) thiophanate methyl acts as endocrine disruptor, affecting the adrenal gland at very low doses, 3) thiophanate methyl may be toxic for nontarget organisms, such as newts.