Characterisation of coral explants: a model organism for cnidarian-

23 24 Coral cell cultures made from reef-building scleractinian corals have the potential to aid in the pursuit 25 of understanding of the cnidarian-dinoflagellate symbiosis. Various methods have previously been 26 described for the production of cell cultures in vitro with a range of success and longevity. In this 27 study, viable tissue spheroids containing host tissue and symbionts (coral explants) were grown from 28 the tissues of Fungia granulosa. The cultured explants remained viable for over two months and 29 showed morphological similarities in tissue structure and internal microenvironment to reef-building 30 scleractinian corals. The photophysiology of the explants (1 week old) closely matched that of the 31 parent coral F. granulosa. This study provides the first empirical basis for supporting the use of coral 32 explants as laboratory models for studying coral symbioses. In particular, it highlights how these 33 small, self-sustaining, skeleton-free models can be useful for a number of molecular, genetic and 34 physiological analyses necessary for investigating host-symbiont interactions at the microscale. 35