Abstract:
Zooxanthellae (Symbiodinium microadriaticum) is very important and necessary for the development and growth of giant clam larvae. Therefore the study on survival rate, growth rate, development and symbiosis establishment have been carried out in giant clam (Tridacna squamosa) larvae to find out the suitable clone of zooxanthellae for giant clam culture. Five clonal cultures of zooxanthellae isolated from sea anemone, staghorn coral, honeycomb coral, mushroom coral and mantle tissue of giant clam were provided for the feeding experiment in giant clam larvae. The study in swimming stage of the larvae showed that the highest survival rate have been found in the larvae fed on zooxanthellae isolated from staghorn coral whereas the highest growth rate in the larvae fed on zooxanthellae isolated from mantle tissue of giant clam. The rapidest larva development to pediveliger stage have been found in the larvae fed on zooxanthellae isolated from honeycomb coral. The complete symbiosis in all treatments occurred within 1214 days, approximately. As for the study in settle stage, the larvae fed on zooxanthellae isolated from honeycomb coral and giant clams mantle have been found the highest survival rate and the rapidest development to juvenile stage at the end of experiments. Furthermore, the highest growth rate in juvenile stage had been observed in zooxanthellae isolated from honeycomb coral and sea anemone. In conclusion, the giant clam larvae would respond differently to zooxanthellae isolated from different hosts and depending on their development stages. The suitable zooxanthellae for giant clam larvae culture was the zooxanthellae isolated from mantle tissue of giant clam and honey comb coral, which resulted in highest survival rate and growth rate, shorten development time and fasten complete symbiosis in larvae.