17th National Symposium on Marine Science
Date:
Title of talk: Symbiodiniaceae diversity associated with Philippine giant clams
Abstract: Giant clams are important components of the reef ecosystem, as they provide food and shelter to other reef organisms. However, due to overharvesting and habitat degradation, several giant clam species are now vulnerable to extinction. Giant clams are closely associated with the microalgae Symbiodiniaceae, which could influence their fitness or susceptibility to environmental change. To better understand the diversity of Symbiodiniaceae in giant clams, we profiled the ITS2 region in eight giant clam species (Hippopus hippopus, H. porcellanus, Tridacna crocea, T. derasa, T. gigas, T. maxima, T. noae and T. squamosa) from eleven sites across the Philippines. Cladocopium was dominant in giant clams at most sites, but Symbiodinium and Durusdinium were also common. Different giant clam species showed variable Symbiodiniaceae composition across sites, except T. gigas, which was mostly associated with Cladocopium only. These findings indicate that giant clam-Symbiodiniaceae associations are generally flexible, and could be an adaptive response to their environment. The specificity of T. gigas for Cladocopium, however, suggests a greater reliance on specific symbionts. This constraint on symbiont association may pose a disadvantage for T. gigas in a changing ocean, thus making this species a top priority for conservation interventions.