In 1981, during the Vietnam-Russia joint survey on the Kallisto ship, a sample of the Tridacna gigas, or giant clam, was collected at Sinh Ton Island in the Spratly Archipelagos. The specimen, weighing 145kg and measuring nearly 1m long, required the assistance of 10 well-equipped specialists to bring it aboard. Following the survey, the Institute of Oceanography retained one piece (currently displayed at the Museum), while the Institute of Marine Resources and Environment kept another.
The giant clam, endemic to the Spratly Sea, owes its large size to the high consumption of sugars and proteins produced by billions of algae living in its tissue. Its thick, hard shell has 4-7 folds running vertically and provides shelter for many small creatures.
According to the Red Book of Vietnam (1992), the conservation status of the giant clam is critically endangered.