Rose danio (Danio roseus): A native Mekong basin alternative to zebrafish for acute, developmental, and...

The fish embryo toxicity test is widely used as an alternative to conventional acute fish toxicity assays, but its ecological relevance may be limited when the model species is nonnative to the region of interest. Here, we evaluated rose danio (Danio roseus), a cyprinid native to the Mekong Basin in Southeast Asia, as a complementary alternative to zebrafish (Danio rerio) for acute and developmental toxicity and neurobehavioral assessment using 3,4‑dichloroaniline, an Organisation for Economic Co-operation and Development (OECD) reference toxicant. Embryos were tested following OECD testing guideline 236 (96 postfertilization), and juveniles were tested following OECD test guideline 203 (96 hr). In embryos, 96‑hr median lethal concentration (LC50) values did not differ significantly between species (zebrafish: 4.04 ± 0.44 mg/L; rose danio: 4.42 ± 0.23 mg/L), yet rose danio showed higher developmental malformation severity at sublethal concentrations. In juveniles, rose danio was more sensitive than zebrafish (96‑hr LC50: 8.04 ± 0.43 vs. 9.84 ± 0.61 mg/L; p < .0001) and exhibited earlier concentration-dependent onset of neurobehavioral impairment (loss of equilibrium with convulsions at higher exposure). Consistent with these outcomes, acetylcholinesterase activity in midgut homogenates was significantly reduced in rose danio but not in zebrafish, whereas glutathione S‑transferase and carboxylesterase were unchanged in both species. Collectively, these results suggest that rose danio may serve as a useful complementary model for toxicity screening and may improve ecological relevance for assessments focused on the Mekong Basin and related Southeast Asian freshwater systems.