Enormous production of cosmetic products and its indiscriminate use tends to discharge into the aquatic environment and might threaten non-target organisms inhabiting aquatic ecosystems. In the study, developmental toxicity of 4-methylbenzylidene camphor (4-MBC), a widely used organic UV filter in personal care products has been evaluated using Zebrafish (Danio rerio). Embryo-larval stages were chosen because they are more sensitive to chemical insult and possibilities of perceiving specific toxicity after toxicants exposure. Zebrafish is a widely used vertebrate model in biomedical and toxicological studies, being a widely accepted model for ecotoxicity evaluation of xenobiotics.
Analysis of zebrafish larvae locomotor activity. Zebrafish larvae locomotor activity was analysed using the WMicrotracker ARENA system (Design plus SRL, Santa Fe, Argentina) based on the protocol described by Bichara et al. (2014). Zebrafish larvae exposed to 4-MBC at 5 dpf and 10 dpf (n = 9 individual for each group) in 24 well plates containing single larvae per well were placed in the WMicrotracker Arena for 60 min at 27 °C and subjected to IR illumination with two infrared micro beams per well (100 μm wide and of 880 nm wavelength). A transient fluctuation in the signal is generated when larvae move across the light beam received by a phototransistor array and analysed the number ofmovements in dark condition. The locomotor activity measurements in 4-MBC exposed zebrafish larvae were repeated three times.
Waterborne exposure induced developmental toxicity and deduced 2.71 mg/L as 96 h LC50 whereas embryos exposed to sub-lethal concentrations (50 and 500 μg/L) caused a significant delay in hatching rate, heart rate, reduced larval length, and restricted hatchlings motility besides the axial curvature. Embryos exposed to sub-lethal concentrations of 4-MBC induced alterations in larval movement: A statistically significant decrease in larval movement was noted at 5 dpf (p < 0.0006) and 10 dpf (p <0.0001) larvae exposed to 500 μg/L concentration. No changes were observed at 5 and 50 μg/L concentrations (Fig. 3A). The results showed that 4-MBC exposure triggers oxidative stress at sublethal concentrations leading to apoptosis, deformities and locomotion perturbations in developing zebrafish.
Ved Prakash, Veena Jain, Shweta Singh Chauhan, Ramakrishnan Parthasarathi, Somendu K Roy, Sadasivam Anbumani