Innovative chips for coral cultivation: Enhanced flexibility and experimental applications

Abstract

Microfluidic systems commenced a new era of coral research, reducing demands for experimental material and minimizing scientific impacts on natural environments. Reduced size also allows continuous microscopy during experiments at unprecedented spatial-temporal resolutions and ensures greater homogeneity of environmental factors among samples. Since the report of the coral-on-a-chip platform in 2016 by Shapiro and colleagues, modifications of coral microfluidic chips have been reported for various experimental purposes. However, existing coral cultivation chips were mostly designed for isolated polyps and for specific experimental setups, limiting their flexibility. Moreover, maintenance of coral health in miniaturized environments has proven challenging, preventing applications of coral chips to experiments with long timescales, which are more relevant to natural environmental events. Here, we present two new coral chips that enable long-term (over a month), stable coral cultivation in the laboratory without laborious maintenance. Through experiments involving several research topics that are of paramount importance, for example flow speed, heating, osmolarity fluctuation and pathogen inoculation, we tested the applicability of our miniaturized system to coral research. Our results demonstrate the usefulness of our miniaturized system with different experimental objectives. Furthermore, by employing coral microcolonies, that is small coral fragments, our system is suitable for a wider spectrum of corals and is compatible with various analyses, compared to polyp-based microfluidic systems in previous studies. The miniaturized system presented here considerably extends the applicability of existing coral cultivation chips and provides a convenient, cost-effective and environmentally friendly platform for future coral studies.