Giant clams, the largest bivalve in the world, occur naturally in association with coral reefs throughout the tropical and subtropical waters of the Indo-Pacific region. From the southeast Pacific westwards to East Africa, its distribution extends up north to the Red Sea (bin Othman et al. 2010). They can generally be found in marine shallow water habitats (1 – 20 m) and are restricted in only clear waters due to their phototrophic characteristic (Jantzen et al. 2008). Their strong requirement of photosynthetic light is a consequence of their symbiotic relationship with zooxanthellae of the genus Symbiodinium (Hirose et al. 2006).
Vulnerable status, or even local extinction, for some species has been reported in Indonesia (Raymakers et al. 2003), Malaysia (Shau-Hwai and Yasin 2003) and several region in Pacific (UNEP-WCMC 2010).
Despite many field observations reporting that seven species of the giant clams inhabit Indonesian waters, the MZB deposits specimens of six species (Tridacna squamosa Lamarck, 1819; T. gigas Linnaeus, 1758; T. derasa Roding, 1798; T. crocea Lamarck, 1819; T. maxima Roding, 1798 and Hippopus hippopus Linnaeus, 1758), suggesting the need for collecting specimen of H. porcellanus Rosewater, 1982. Important characters to distinguish species among Tridacninae are interlocking teeth on byssal orifice, life habits, presence of scales and inhalant siphon tentacles.
For more details, visit the journal site here (http://biodiversitas.mipa.uns.ac.id/D/D1303/D130303.pdf)