Development of long-term oyster explant cultures enable sustained tissue-specific activity and reveal novel cellular behaviours.

Molluscs are ecologically and economically important, yet progress in understanding their cellular biology has been limited by the lack of reliable cell culture systems. Here, we establish reproducible long-term in vitro and ex vivo cultures from multiple tissues of the European flat oyster, Ostrea edulis, including heart, visceral mass, mantle, and gill. Explanted tissues remained intact and exhibited tissue-specific function for over two months, with whole hearts maintaining rhythmic contractions for up to nine months. Cultures revealed cellular plasticity, including haemocyte granule turnover, auricular epithelial remodelling with novel ciliation, and the emergence of multicellular microtissues. Previously understudied cell types, including visceral mass adipocytes and mantle myocytes, were maintained in culture, expanding the cellular repertoire accessible in vitro. These systems provide a tractable platform for future molluscan studies, while establishing a foundation for comparative invertebrate cell biology and the future development of immortalised molluscan cell lines.