Discovery of Symbiodiniaceae symbiosis in the mangrove mud clam Geloina expansa (Mousson, 1849) from Kerala, India

To our knowledge, this study provides the first microscopic evidence of symbiotic association between Geloina expansa and endosymbiotic dinoflagellates (zooxanthellae). Mangrove ecosystems, recognized for their ecological complexity and biodiversity, host numerous interactions, yet this symbiotic association with Symbiodiniaceae has not been previously documented. The presence of Symbiodiniaceae in the mantle and gill tissues of G. expansa represents a previously undocumented association in mangrove clams and provides a foundation for future investigations into its ecological and physiological significance. By revealing a previously unrecognized clam–algae association, this study emphasizes the importance of investigating symbiotic relationships that influence ecosystem structure, function, and conservation value.