Toxicological Effects of Diuron Exposure on Javanese Medaka (Oryzias javanicus): Insights from a Tropical Estuarine Fish Model
Nur Amiera Kamarudin *
International Institute of Aquaculture and Aquatic Sciences (I-AQUAS), Universiti Putra Malaysia, Teluk Kemang, 71050, Port Dickson, Negeri Sembilan, Malaysia and Department of Biology, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Syaizwan Zahmir Zulkifli
Petroliam Nasional Berhad, Level 13, Tower 1, PETRONAS Twin Tower 1, KLCC, 50088 Kuala Lumpur, Malaysia.
Ferdius Mohamat Yusuff
International Institute of Aquaculture and Aquatic Sciences (I-AQUAS), Universiti Putra Malaysia, Teluk Kemang, 71050, Port Dickson, Negeri Sembilan, Malaysia and Department of Environment, Faculty of Forestry and Environment, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Ahmad Ismail
Academy of Sciences Malaysia, MATRADE Tower, Jalan Sultan Haji Ahmad Shah, off 15 Jalan Tuanku Abdul Halim, 50480 Kuala Lumpur, Malaysia.
*Author to whom correspondence should be addressed.
Abstract
Diuron, a biocide widely used in agriculture and offshore industries, can cause acute toxicity in aquatic organisms, leading to fatal outcomes and behavioural disruptions. This study assessed its toxic effects on Javanese medaka (Oryzias javanicus) to determine safe exposure levels and support guideline development for Malaysian river and coastal waters. Eight triplicate treatments were prepared, each with 10 individuals (mean size 3.0 ± 0.3 cm, n = 240) exposed to 1.0 to 20.0 mg/L concentrations. Acute toxicity was evaluated over 96 hours using probit analysis to calculate the median lethal concentration (LC₅₀), which was found to be 5.90 mg/L. No mortality occurred in the control groups. Behavioural endpoints—including surfacing, burst swimming, loss of coordination, and pigmentation changes—were significantly observed in the exposed groups, with noticeable responses beginning at 5.0 mg/L compared to the control. The results highlight the high sensitivity of O. javanicus to this herbicide, supporting its suitability as a bioindicator species for aquatic toxicants. Due to its ecological adaptability and sensitivity, Javanese medaka is a valuable tropical model for ecotoxicological research in Malaysia.
Keywords: Herbicide, lethal toxicity, probit analysis, bio-monitoring agents, ecotoxicology, biocide