Embedded Tridacna crocea (Photo: Lisa Kirkendale)

Boring Giant Clam

Tridacna crocea

Shell large (L 12.5-15 cm), solid, inflated, triangular ovate, inequilateral. Very large broad byssal gape, ~6-10 broad low radial rib like folds, with close set undulating scales (often eroded). Numerous riblets on folds and interstices result in almost smooth appearance. Exterior dull grey white, while interior often tinted with bright hues of orange, peach, yellow or pink. Incurrent aperture with indistinct guard tentacles.

Morphology

Smallest giant clam species, with medium, heavy robust shell, nestled into coral heads, unique characteristic lifestyle for giant clams. Byssal attachment in adulthood facilitates this mode of existence. Hypertrophied mantle that is brilliantly colored and extending beyond shell margin. Large siphons, responsive to movement. Photosymbiotic.

Evolution

Sister to T. squamosa.

Behaviour

Water jetting via large siphons in response to movement.

Method of reproduction

Broadcast spawner.

Habitat

Marine

Unique habitat compared to other giant clams. Called the boring giant clam as it through chemical and physical means settles, attaches with byssus and ends up existing flush with surface of coral/bommie.

Distribution

QLD, NT and WA in Australia, but widely distributed in the Indo-west Pacific.

Life Cycle

Hermaphroditic. Veliger larvae acquire photosymbionts from the environment.

Taxonomy

Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Subclass: Heterodonta
Superorder: Imparidentia
Order: Cardiida
Superfamily: Cardioidea
Family: Cardiidae
Subfamily: Tridacninae
Genus: Tridacna
Species: crocea
Name Published Year: 1819
Rank: species
Scientific Name Authorship: Lamarck
Commercial Impact: 

Aquarium trade, shell trade

Conservation Assessment: Least Concern

Net Conservation Benefits Fund

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Western Australian Museum Collections https://museum.wa.gov.au/online-collections/names/tridacna-crocea
Accessed 10 May 2025

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References

Herrera, N.D., Poorten, J.J. ter, Bieler, R., Mikkelsen, P.M.,Strong, E.E., Jablonski, D., & Steppan, S.J. (2015). Molecular phylogenetics and historical biogeography amid shifting continents in the cockles and giant clams (Bivalvia: Cardiidae). Molecular Phylogenetics and Evolution, 93, 94-106.

Lamprell, K., & Whitehead, T. (1992). Bivalves of Australia. Vol. 1. Bathhurst, New South Wales: Crawford House Press.

Lucas, J.S. (1988). Giant clams: description, distribution and life history. pp. 21-32 In Copland, J.W. & Lucas, J.S. (eds). Giant Clams in Asia and the Pacific. Canberra: ACIAR.

Persselin, S.L. (1998). The evolution of shell windows within the Fraginae (Bivalvia: Cardiidae) and the origin of algal symbiosis in cardiids. M.S. Thesis in Biology, University of Guam.

Poorten, J.J. ter. (2009). The Cardiidae of the Panglao Marine Biodiversity Project 2004 and the Panglao 2005 Deep-Sea Cruise with descriptions of four new species (Bivalvia). Vita Malacologica, 8, 9-96.

Rosewater, J. (1965). The Family Tridacnidae in the Indo-Pacific. Indo-Pacific Mollusca, 1, 347-408. Sharabati, D. (1984). Red Sea Shells. London : KPI Limited. Tan, S.K., & Low, M.E.Y. (2014). Checklist of the Mollusca of Cocos (Keeling) / Christmas Island ecoregion. Raffles Bulletin of Zoology, suppl., 30, 313-375.

Willan, R.C., Bryce, C., & Slack-Smith, S.M. (2015). Kimberley marine biota. Historical data: molluscs. Records of the Western Australian Museum, Supplement, 84, 287-343. http://www.gizmag.com/giant-clams-color-displays-solar-cells/41394/ https://www.dpaw.wa.gov.au/management/marine/marine-parks-wa/fun-facts/4... IUCN red list assessment-

Mollusc Specialist Group. 1996. Tridacna crocea. The IUCN Red List of Threatened Species 1996: e.T22135A9361892. http://dx.doi.org/10.2305/IUCN.UK.1996.RLTS.T22135A9361892.en. Downloaded on 14 October 2016.