Abstract
Etridiazole (EDZ), a thiadiazole-containing toxic chemical, is widely used as a fungicide. Regular usage of EDZ may reach and contaminate water bodies, but its adverse effects on aquatic vertebrates have not been well studied. Therefore, the present study aimed to evaluate the harmful effects of EDZ using zebrafish (ZF) (Danio rerio) embryos. ZF embryos were treated with 3.75, 7.5, 15, 30, and 60 mg/L of EDZ. Subsequently, mortality and developmental toxicities were quantified at 24, 48, 72, and 96 h post fertilization (hpf). The results showed that embryo mortality was concentration- and time-dependent. The median lethal concentration (LC50) of EDZ at 96-h was 25.58 ± 1.49 mg/L. Besides, EDZ induced a series of morphological deformities, including abnormal somite formation, abnormal eye pigmentation, abnormal tail morphology, tail kinks, skeletal malformations (lordosis, kyphosis, and scoliosis), and yolk sac edema in a concentration-dependent manner. Among the deformities, the most significant were reduced heartbeat and increased incidence of pericardial edema. The median effective concentration (EC50) of EDZ at 96-h was 17.93 ± 2.22 mg/L and the 96-h teratogenic index (TI) value was 1.52. Taken together, these results indicate that EDZ is a teratogen, and primarily affects the cardiovascular system of ZF.
Highlights
The use of thiadiazoles and thiadiazole derivatives as pesticides has been rising worldwide
The present study investigated the adverse effects of EDZ on ZF embryos by scoring multiple phenotypical endpoints after 24, 48, 72, and 96 h of exposure to EDZ
The results obtained in this study demonstrate that EDZ could cause several developmental deformities at a concentration significantly lower than the concentration that induces mortality
Summary
The use of thiadiazoles and thiadiazole derivatives as pesticides has been rising worldwide. Etridiazole (EDZ), 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole, has been widely used as a fungicide for the control of Pythium and Phytophthora species on agricultural and horticultural crops [1]. In addition to its agricultural usage, EDZ is widely applied to the golf course turf at a relatively high level (1 g/0.93 m2 for every 10–14 days), raising the concern that the golf course runoff may reach surface water, posing a serious threat to non-target aquatic organisms. Etridiazole has been observed to adversely affect body weight gain, viability, and skeletal formation in rabbit fetuses [1]. EDZ is known to affect the liver-to-body weight ratio in both rats and dogs [5]. Trichloro acetonitrile (TCAN), a precursor of EDZ, is known to induce embryonic lethality, fetal weight reduction, and cardiovascular anomalies in rats [6]. Studies on Salmonella typhimurium and Chinese hamster ovary cells after EDZ
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