Bioaccumulation mediated by water solubility leads to differences in the acute toxicity of organophosphorus insecticides to zebrafish (Danio rerio).

The use of some organophosphate insecticides is restricted or even banned in paddy fields due to their high toxicity to aquatic organisms. The aim of this study is to elucidate the main pathways and target organs of organophosphate insecticide toxicity to fish exposed via different routes by integrating histopathological and biochemical techniques. Using malathion as the model drug, when the dosage is 20-60 mg/L, the toxicity of whole body and head immersion drugs to zebrafish is much higher than that of trunk immersion drugs. A dose of 21.06-190.44 mg/kg of malathion feed was fed to adult zebrafish. Although the dosage was already high, no obvious toxicity was observed. Therefore, we believe that the drug mainly enters the fish body through the gills. When exposed to a drug solution of 20 mg/L and 60 mg/L, the fish showed significant neurological behavioral abnormalities, and the pathological damage to key organs and brain tissue was the most severe, showing obvious vacuolization and the highest residual amount (8.72-47.78 mg/L). The activity of acetylcholinesterase was the most inhibited (54.69-74.68%). Therefore, brain tissue is the key toxic target organ of malathion in fish. In addition, we compared the bioaccumulation effects of different water-soluble organophosphorus insecticides in fish and their toxic effects. We found that the higher the water solubility of organophosphorus insecticides, the lower their toxicity to fish.

Identification of Polymorphisms in the HERC2-OCA2 Gene Locus and their Association with Feather Color in Quail.

Mutations in the HERC2 and OCA2 genes have the potential to affect pigment deposition and alter feather color in birds. Therefore, in this study, we evaluated HERC2-OCA2 gene locus polymorphisms in Korean and Beijing white quails using RNA-Seq and KASP technology. The expression levels of HERC2 and OCA2 mRNA in skin tissues were analyzed using RT-qPCR. Ten single nucleotide polymorphisms were identified by RNA-Seq, of which three (n.117627564T>A, n.117674275T>G, n.117686226A>C) exhibited significant association with feather color in quail. The expression of OCA2 mRNA was significantly lower in the skin of Beijing white quails than that in the skin of Korean quails. These results suggested that variants in HERC2-OCA2 intergenic region could influence the expression of OCA2, which may underlie diluted feather color in the Beijing white quail.