The
Tridacninae are a
subfamilyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of Bivalves colloquially known as
giant clams. The family contains the biggest bivalve species, including
Tridacna gigas, the
giant clamThe giant clam, Tridacna gigas , is the largest living bivalve mollusc. T. gigas is one of the most endangered clam species. It was mentioned as early as 1825 in scientific reports...
. They have heavy shells, fluted with 4–6 folds. Mantle is usually brightly coloured. They inhabit coral reefs in warm seas of the
Indo-PacificThe Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
region. In some areas, such as the
PhilippinesThe Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, members of the family are farmed for the
marine aquariumA marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only , fish only with live rock , and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally...
trade. Most of them live in
symbiosisSymbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
with photosynthetic
dinoflagellateThe dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...
s (
zooxanthellaZooxanthellae are flagellate protozoa that are golden-brown intracellular endosymbionts of various marine animals and protozoa, especially anthozoans such as the scleractinian corals and the tropical sea anemone, Aiptasia....
e).
Systematics
Sometimes the giant clams are still treated as a separate family
Tridacnidae, but modern phylogenetic analyses included them in the family Cardiidae as a subfamily.
Two recent genera and eight species are known:
- Hippopus
Hippopus is a genus of large tropical saltwater clams, marine bivalve mollusks in the family Tridacnidae, the giant clam family....
- Tridacna
Tridacna is a genus of large and gigantic saltwater clams, marine bivalve mollusks in the subfamily Tridacninae, the giant clams. They have heavy shells, fluted with 4–6 folds. Mantle is brightly coloured. They inhabit shallow waters of coral reefs in warm seas of the Indo-Pacific region...
Recent genetic evidence has shown them to be monophyletic sister taxa.
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