Giant Clams and Marine Bivalves Codexery

Giant clam

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Giant clam

Fernando Losada Rodríguez · via Wikipedia: Giant clam · CC BY-SA 4.0

The giant clam is a large bivalve native to shallow coral reefs of the South Pacific and Indian oceans, where it may exceed 200 kg and 120 cm across.[1] Its mantle tissues host symbiotic algae that provide most of the adult clam's nutrition.[2][3]

Scientific classification

  1. KingdomAnimalia
  2. PhylumMollusca
  3. ClassBivalvia
  4. OrderCardiida
  5. FamilyCardiidae
  6. GenusTridacna
  7. SpeciesTridacna gigas

Named by (Linnaeus, 1758)

Close relatives

Other species of Tridacna with a Codexery entry.

Sources: Wikipedia taxobox: Giant clam (CC BY-SA 4.0) · order, family and genus agree with WoRMS AphiaID 207670 (CC BY 4.0)

Conservation status

Critically Endangered (CR)

  1. LC
  2. NT
  3. VU
  4. EN
  5. CR▲ this species
  6. EW
  7. EX
Population trend
Not held in our sources — see the assessment
Assessment published
2024

Source: IUCN Red List assessment · GBIF copy of the Red List category

How big is it?

Size comparison: Giant clam and a personA 1.37 m long giant clam drawn to scale next to a 1.8 m tall person. Schematic shapes, not a likeness.1.37 m1.8 m

Largest length in the source, 1.37 m, next to a 1.8 m person.

Diagram: drawn by Codexery, schematic shapes to scale (not a likeness). Length: Wikipedia: Giant clam

Where the giant clam has been recorded

Where the giant clam has been recorded164 mapped locations from 1,639 GBIF occurrence records; marked places: Pacific Ocean, Ishigaki IslandPacific OceanIshigaki Island

Each dot is a place where the species has been observed and reported (1,639 records, half-degree grid) — not a modelled range. 14 inland records left out (institution coordinates). 1 isolated far-off record not drawn.

Map: drawn by Codexery. Data: GBIF occurrence search (records CC0 / CC BY) · Natural Earth basemap (public domain) · place coordinates: Wikipedia (CC BY-SA 4.0)

Key facts and history

The fertilized egg hatches into a trochophore larva after about 12 hours.[4] Intensive exploitation by bivalve fishers is the main reason giant clams are becoming endangered.[4] For thousands of years, indigenous peoples in East Asia were familiar with these clams, and the Venetian explorer Antonio Pigafetta wrote about them in a journal entry from 1521.[1] The dead largest known specimen had a length of 137 cm and a mass of 230 kg; its living mass was estimated at 250 kg.[5]

A heavier dead clam, with a shell length of 115 cm and a mass of 333 kg, was discovered in 1956 off Ishigaki island.[4] Once a clam attains a length of 20 cm, it is classified as a juvenile.[6] The giant clam itself is regarded as a delicacy in Japan, France, Southeast Asia, and many Pacific Islands.[4]

What the cited sources add

The National Geographic Society account notes that giant clams achieve their size by consuming sugars and proteins from algae in their tissues.[7] Barnett's Atlas Obscura article describes that in Palau, giant-clam shell makes up more than three-fourths of some of the oldest shell middens.[8] The same source recounts that Palauan creation lore began with a giant clam that sired Latmikaik, the mother of human children.[8] Barnett also explains that the scientific name Tridacna comes from Greek words meaning "three bites," referring to humans biting the clam, not the reverse.[8]

A 2019 study found that fecal pellets from adult giant clams contain symbiotic algae that can be transmitted to juveniles.[3] That study suggests giant clams could supply heat-resistant algae to coral reefs to mitigate bleaching.[3]

References

  1. Wikipedia, "Giant clam" (CC BY-SA 4.0), which cites: "Giant Clam: Tridacna gigas", National Geographic Society, 10 June 2011; Syukri bin Othman, "THE DISTRIBUTION AND STATUS OF GIANT CLAMS (FAMILY TRIDACNIDAE) – A SHORT REVIEW", The Raffles Bulletin of Zoology, 28 Feb 2010, p. 103–111 (we also read that source) en.wikipedia.org
  2. Wikipedia, "Giant clam" (CC BY-SA 4.0), which cites: Lucas, "The biology, exploitation, and mariculture of giant clams (Tridacnidae)", Reviews in Fisheries Science, January 1994, p. 181–223 (original not read by us) en.wikipedia.org
  3. "Giant Clams' Poop Hosts Symbiotic Algae", 5 September 2019. facts only, no text reused. asianscientist.com
  4. Wikipedia, "Giant clam" (CC BY-SA 4.0), which cites: Knop, "Giant clams: a comprehensive guide to the identification and care of Tridacnid clams", Dähne Verlag, 1996 (we also read that source) en.wikipedia.org
  5. Wikipedia, "Giant clam" (CC BY-SA 4.0), which cites: Knop, "Giant clams: a comprehensive guide to the identification and care of Tridacnid clams", Dähne Verlag, 1996; McClain, "Sizing ocean giants: patterns of intraspecific size variation in marine megafauna", PeerJ, 2015-01-13 (we also read that source) en.wikipedia.org
  6. Wikipedia, "Giant clam" (CC BY-SA 4.0), which cites: Knop, "Giant clams: a comprehensive guide to the identification and care of Tridacnid clams", Dähne Verlag, 1996; Beckvar, "Cultivation, spawning, and growth of the giant clams Tridacna gigas, T. Derasa, and T. Squamosa in Palau, Caroline Islands", Aquaculture, 1981, p. 21–30 (we also read that source) en.wikipedia.org
  7. "Giant Clam: Tridacna gigas", National Geographic Society, 10 June 2011. facts only, no text reused. nationalgeographic.com
  8. Barnett, "The History, Myth, and Future of the Giant Clam", Atlas Obscura, 2021-07-06. facts only, no text reused. atlasobscura.com

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Giant clam (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

Related entries

Same family (Cardiidae)

Hippopus hippopus Hippopus hippopus

Named in this entry

Genus

More in Giant Clams and Marine Bivalves

Maxima clamTridacna noaeTridacna rosewateriTridacna squamosaTridacna squamosinaArgopecten gibbusArgopecten irradiansArgopecten purpuratusChlamys hastataChlamys rubidaTridacninaeHippopus

Sources

Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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