Zooxanthellae diversity and its effects on the survivorship and growth rate of giant clams larvae

Giant clams (Fam. Tridacnidae) live in association with zooxanthellae. These algae have the capability of transferring part of their photosynthetic product to their host. Therefore, zooxanthellae also known as important source of energy for the clams. It has been reported that there were several different types of zooxanthellae isolated from corals. However, no study has been conducted to investigate the diversity of zooxanthellae of Indonesian giant clams. The present study aimed to investigate the diversity of zooxanthellae isolated from giant clams, and its effects on the survival and growth rate of giant clams larvae. The results showed that there were two different genotypes of zooxanthellae isolated from 4 species of giant clams. Tridacna crocea, Hippopus hippopus and H. porcellanus had the same genotype of zooxanthellae, which was different with zooxanthellae isolated from T. squamosa. When these algae were introduced to giant clams larvae, it was found that zooxanthellae isolated from T. squamosa increased the survival and growth rate of the larvae. Keywords: zooxanthella �survivorship �giant clams larvae �growth rat