Giant Clam

Spectacular behemoths of Tubbataha

Giant clams (Tridacna gigas), locally known as “taklobo”, are the largest and heaviest living bivalve mollusk in the world.  They grow to about 120 cm across and weigh more than 200 kg.  Due to its size, it has been historically misunderstood.  Legend has it that many deaths were caused by these “man-eating clams” to divers who got trapped inside their giant shells.

But, contrary to legends, giant clams were extensively harvested for food and the aquarium trade. Declines of population in the wild have been reported. In recent years, efforts have been undertaken to conserve them through artificial breeding.

tubbataha tridacna gigas

Tubbataha marine park rangers found this giant clam (Tridacna gigas) at the shallow part of the reef.

Giant clams are one of the most ecologically important organisms in coral reef ecosystems such as Tubbataha. As filter feeders, they siphon significant volumes of water, clean excessive amount of nutrients and maintain good water quality.  Similar to reef-building (hermatypic) corals, giant clams have single-celled dinoflagellates called zooxanthellae living within their tissues.  These symbiotic algae provide supplementary nutrients to the animals through photosynthesis and contribute to animal growth and to the reef structure as a whole. These zooxanthellae also allow the clams to show off a multitude of iridescent colors in their mantle that truly earned them their name “Spectacular Behemoths”.