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Related FAQs:  Tridacnid Identification, Tridacnid Behavior, Tridacnid Selection, Tridacnid Compatibility, Tridacnid Systems, Tridacnid Lighting, Tridacnid Placement, Tridacnid Feeding, Tridacnid Disease, Tridacnid Disease 2, Tridacnid Health 4, Tridacnid Health 5, & Tridacnid Reproduction, Giant Clams, Tridacnids 2, Tridacnids 3, Tridacnids 4, Tridacnid Clam BusinessBivalves, Bivalves 2, Lighting Marine Invertebrates,

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/The Conscientious Marine Aquarist

The Giant Clams, family Tridacnidae

Bob Fenner

   Tridacna gigas, Australia

Superfamily Tridacnacea, Family Tridacnidae, the Giant Clams

    Typically with heavy shells of a convoluted nature, often ribbed on their outside with scales. Mainly found associated with stony corals, sometimes embedded in their matrix. 

Tridacnid mantle. The extension of the mantle encourages photosynthesis by symbiotic zooxanthellae located in the Clam's tissues; removing carbon dioxide to supply the algae, who in turn produce oxygen and sugars for the Clam. 

Hippopus hippopus (Linnaeus 1758), the China Clam. Malay Peninsula to Australia, out to Micronesia and Tonga. Found in shallows on reef flats and patch reefs. To sixteen inches shell width. No large opening at the shell base. Brownish mantle with many fine white lines of its surface.  This one in captivity.

Tridacna crocea Lamarck 1819, the Crocus Giant or Burrowing Clam. Malay Peninsula to the GBR; Philippines, Guam, Fiji. Distinguished by having about six rounded ribs highly adorned with fluted scales. Small species; to about six inches across. Filter feeder that also utilizes photosynthates. A couple in captivity and a close-up taken in Australia's Great Barrier Reef.

Tridacna derasa (Ruding 1798), the Derasa Clam. Cocos Keeling, Australia, Fiji, Indonesia and the Philippines. Very low sculpturing on the shell, which has its base near the anterior end rather than posterior (as all other species of Tridacna). Shells can close tightly together (unlike T. gigas). Often yellow/golden streaking in mantles.

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Tridacna gigas (Linnaeus 1758), the Giant Giant Clam. Smooth shell with no concentric sculpturing. The largest bivalve and mollusk in the world at up to 1.3 meter in length. Malay Peninsula to Marshalls and Fiji. At right: One in an exhibit at the Waikiki Aquarium, Honolulu, Hawai'i, and a big-boy (about four feet across) at "Cod Hole", in the Coral Sea, north of Cairns, Queensland, Australia, and a four incher at Barry Neigut's Clams Direct business in San Diego, CA. Below a really big valve of a gigas at Marty Beals Tideline in Los Angeles (137 kg. about 41" across at the widest... and BobF... too heavy and wide as well... Photo by James Fatherree. Oh, James says the world's record is 54"/137cm. wide and much, much heavier (220 kg.s)... More than RMF by far!

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Tridacna maxima (Roding 1798), the Large Giant Clam. Has well-developed concentric growth folds. South Africa to the Red Sea out to the Line Islands, but not in Hawai'i. Common in its range.  To about sixteen inches in diameter.  Characterized by elongate, triagonal shells, dense, narrow-spaced folds on the shells (wavy appearance). Fiji and Red Sea and captive juvenile images below.
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Tridacna squamosa Lamarck 1819, the Fluted Giant Clam. Distinguished by the presence of large leaf-like fluted edges on its shell. South Africa to the Red Sea to the Marshall Islands. To sixteen inches across.  Relies on photosynthesis for a major part of its nutrition.  Below: These in Pulau Redang, Malaysia are near full size. Next, aquarium and Red Sea images.
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Bibliography/Further Information:


Here's James Fatherree and Barry Neigut out in front of the latter's San Diego-based Clams Direct business location... both have been working on a Tridacnid Husbandry book for ages... when will Knop's decade old work be supplanted? Pic by RMF... Oh, is now! 2006.

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