Establishing simple image-based methods and cost-effective instrument for toxicity assessment on circadian rhythm dysregulation in fish

Abstract

Analysis of circadian rhythm behavior alteration in fish for toxicity assessment usually requires expensive commercial equipment and laborious and complicated tweaking. Here, we reported a simple set-up that consists of a custom-made light box equipped with white and 940 nm light emitting diodes (LED) light strips as light sources and the locomotion activities of zebrafish or catfish were captured by using infrared-sensitive coupled charged device (CCD). The whole set-up was housed in a temperature-controlled incubator to isolate external noise and to maintain consistent experimental conditions. The video recording and light triggering was synchronized by using Total Recorder, a recording scheduling software. By using the set-up mentioned above and open source software such as ImageJ or idTracker, the locomotion activities of diurnal (e.g. zebrafish) and nocturnal (e.g. catfish) fish at day and night cycles can be quantitatively analyzed. We used this simple image-based methods and cost-effective instrument to assess circadian rhythm of multiple fish species, as well as other parameters such as age, ambient temperature and chemical toxicology with high precision and reproducibility. In conclusion, the instrument setting and analysis method established in this study provide a reliable and easy entry point for toxicity assessment on circadian rhythm dysregulation in fish.