Impact of ketamine on the behavior and immune system of adult medaka (Oryzias latipes) at environmentally relevant concentrations and eco-risk assessment in surface water

Abstract

This work for the first time investigated the bioconcentration factor (BCF), toxicity, and eco-risk of KET using adult medaka fish (Oryzias latipes) as model organism after exposure at environmental concentrations (0.05–0.5 μg L−1) and higher levels (5–100 μg L−1) for 90 days. The BCF of KET was approximately 1.07- to 10.94- folds. The behavioral functions, including swimming properties, feeding rate, and food preference, were significantly impacted by KET (≥0.05 μg L-1). After 90-days exposure, KET induced histological abnormalities in liver and kidney tissue at 0.1 and 0.2 μg L−1, respectively. Additionally, the condition factor, hepatic-somatic index (HSI), and nephric-somatic index (NSI) of medaka were markedly impacted by KET treatment at 0.5, 0.5, and 0.1 μg L−1, respectively. Morphological inflammation (i.e., haemorrhage and erosion) in the fish body was observed exposed to KET, and the EC10 value was 0.407 μg L−1. Alterations in the expressions of genes (i.e., cacna1c, oxtr, erk1, and c-fos) and proteins (i.e., OXT and PKA), involved in in calcium ion channels induced by KET, could partly elucidate the underlying mechanism of the toxicity. The inflammatory risk to fish posed by KET in some rivers in southern China was at high level, suggesting the long-term concentration monitoring was required.