Thiobencarb-induced embryotoxicity in medaka (Oryzias latipes): stage-specific toxicity and the protective role of chorion.

摘要: Abstract Thiobencarb ( S -(4-chlorobenzyl)- N , -diethyl thiol carbamate) has been one of the herbicides previously associated with fish kills in agricultural drains near Sacramento/San Joaquin rivers and their Delta. This area is an important spawning ground for fish, thus there are concerns over possible toxic effects on early life stages fishes. To define targets thiobencarb embryotoxicity to determine degree protection afforded by chorion, medaka Oryzias latipes ) embryos were exposed under static nonrenewal conditions. Responses exposures initiated at blastula or initiation heart beat (stages 10 23, respectively) assessed. In addition, enzymatically dechorionated (stage 13, gastrula) compared responses intact chorions. Embryos observed daily development gross abnormalities including: bradycardia, pericardial edema, hemostasis, poor yolk resorption, cephalic spinal deformities, abnormal hatching. A subset was also evaluated histologic alterations. Based abnormalities, concentration affecting 50% (EC 50 3.6 mg/l, while putative no observable effect (NOEC) 1.0 mg/l. For onset 23), these values 4.1 2.5 respectively. Dechorionated tended be more sensitive than chorionated cohorts (LC =2.5 vs. mg/l). Liver alterations seen EC levels higher. Stage-specific toxicity evident; nevertheless, NOEC treated stage 23 similar.