Early-life exposure to toxic chemicals causes irreversible morphological and physiological abnormalities that may last for a lifetime. The present study aimed to determine the toxicity effect of 3,4-Dichloroaniline (3,4-DCA) on Javanese medaka (Oryzias javanicus) embryos. Healthy embryos were exposed to various 3,4-DCA concentrations for acute toxicity (5, 10, 25, 50, and 100 mg.L-1) and sublethal toxicity (0.10, 0.50, 1.25, 2.50, and 5.00 mg.L-1) for 96 h and 20 days respectively. Acute toxicity test revealed that the median lethal concentration (96h-LC50) was 32.87 mg.L-1 (95 % CI = 27.90-38.74, R2 = 0.95). Sublethal exposure revealed that 1.25 mg.L-1 at 3 days post-exposure (3 dpe) has a significant lower heartrate (120 ± 12.3 beats/min., p < 0.01), while at 7 dpe those exposed to 5 mg.L-1 (141.8 ± 8.3 beats/min) had significantly (p < 0.01) lower heart rate compared to other treatments. Likewise, at 13 dpe, 5.00 mg.L-1 (110.4 ± 17.3 beats/min) and 2.5 mg.L-1 (130.4 ± 8.3 beats/min) were significantly lower (p < 0.001) compared to control. None of the embryos in 5.00 mg.L-1 and 2.50 mg.L-1 treatment groups survived at the end of the experiment. The results indicated a concentration-dependent response. The lowest observed effect concentration (LOEC) that exerted developmental deformities was 0.5 mg.L-1. Javanese medaka embryo have low sensitivity to acute toxicity of 3,4-DCA, but developmental abnormalities at sublethal concentrations were observed.
Authors: Musa Adamu Ibrahim, Syaizwan Zahmir Zulkifli, Mohammad Noor Amal Azmai, Ferdaus Mohamat-Yusuff, Ahmad Ismail
; Full Source: Toxicology reports 2020 Aug 16;7:1039-1045. doi: 10.1016/j.toxrep.2020.08.011.