Tridacna maxima   Roding,  1798 (Clam)
Organism information awaits expert curation
Class: Bivalvia

Size: Maximum shell length 35 cm, commonly to 25 cm.

Color: Exterior of shell greyish white, often suffused with yellow or pinkish orange and strongly encrusted with marine growths. Interior porcelaneous white, sometimes with yellow to orange hues on margins. Dorsally exposed mantle area of living specimens is often brightly colored and variable in color and pattern.

Shell moderately large and inflated, strongly inequilateral and highly variable in shape, usually elongate-ovate to somewhat triangular in outline. Umbones markedly anterior in position, generally situated about the anterior 1/3 of shell length. Posteroventral margin of valves with a large byssal orifice, bordered by 4 to 9 small, distinct to obsolete and non-interlocking crenulations, which become more distantly set posteriorly. Dorsal free margin widely arched and deeply undulated, with a series of 5, usually sharply triangular, inter-digitating projections which represent the extremities of radial furrows of the outer sculpture. Posteroventral area not set off by a distinct radial ridge or angulation, with crowded radial sculpture that results in crenulations on the internal margins at posterior end of shell. Outer surface of each valve has 6 or 7 very broad, moderately convex, rib-like radial folds, bearing closely set, erect but low, concentric scales. Scales developed on entire shell, although often more or less strongly eroded, especially near the umbones. Secondary sculpture of closely spaced, undulate concentric lines of growth, and weak radial riblets, 8 to 20 in number on the main ribs and 3 to 7 on the rather narrow interstices of ribs. Posterior pedal retractor scar relatively large, more than half the size to frequently sub equal to posterior adductor scar. Inhalant (posterior) siphonal opening has tentacles.

Zooxanthellae, a photosynthetic algae live symbiotically within the mantle of the clam. Tridacna maxima mainly derives its nutrition mainly through photosynthesis, which is performed by the zooxanthellae.

Synonym (s)
Tridacna elongata Lamarck 1819
Tridacna (Chametrachea) maxima (Roding, 1798)
Tridacna acuticostata G.B. Sowerby III, 1912
Tridacna elongatissima Bianconi, 1856
Tridacna fossor Hedley, 1921
Tridacna troughtoni Iredale, 1927

Common Name (s)
• Maxima Clam (English)
• Elongate Gaint Calm
Economic Importance and Threats
Importance:  Commercial
(Collected for food and for the shell trade.)
Cultured:  Yes

Habitat:  Reef Associated
Trophic Level:  Primary Consumer
Prey:  Plankton


• Karnataka, Netrani Island (Lat: 14) (Long: 74.32) INDIA (Record: 10/05/2006) (Depth: -(12-15) mts)
• Lakshadweep, Minicoy INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Suheli INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Kalpeni INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Kavaratti INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Agatti INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Bangaram INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Bitra INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Chettalatt INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Kiltan INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Kadamatt INDIA (Record: 01/1987-03/1987)
• Lakshadweep, Amini INDIA (Record: 01/1987-03/1987)
• Tamil Nadu, Gulf of Mannar (Lat: 78.13) (Long: 8.58) INDIA (Record: 01/1994-12/1995)
• Tamil Nadu, Gulf of Mannar (Lat: 79.5) (Long: 9.33) INDIA (Record: 01/1994-12/1995)

Literature Source(s)
  • Tikadar, BK; Daniel, A and Subbarao, NV (1986) Sea shore animals of Andaman and Nicobar Islands The Director, ZSI, Kolkatta 188 Available at - ZSI, Pune
  • Alfred, JRB; Das, AK and Sanyal, AK (Eds.) (1998) Faunal diversity in India ZSI, Calcutta 1-497 Available at - NCL, Pune
  • Subba Rao, NV and Dey, A (2000) Catalogue of marine molluscs of Andaman and Nicobar Islands Occasional paper no 187 Records of the Zoological Survey of India ZSI 1-323 Available at - NCL, Pune
  • UNEP World Conservation Monitoring Centre Available at -
  • Tikader, BK and Das, AK (1985) Glimpses of animal life of Andaman and Nicobar Islands ZSI, Kolkata 1-170 Available at - NCL, Pune
  • Oliver, PG; Holmes, AM; Killeen, lJ and Wood, H (2004) Annotated checklist of the marine Bivalvia of Rodrigues Journal of Natural History Taylor and Francis 38 3229-3272 Available at -
  • Tan, KS and Kastoro, WW (2004) A small collection of gastropods and bivalves from the Anambas and Natuna Islands, south China Sea The Raffles Bulletin of Zoology 11 47-54
  • Vazirani, TG (1977) Notes on a collection of Dytiscidae (Coleoptera) from Maharashtra, with description of a new species Records of the Zoological Survey of India 73(1-4) 123-133
  • Sealifebase Available at -
  • Hosseinzadeh, H; Daghoghi, B and Rameshi, H (2001) Atlas of the Persian Gulf molluscs Oman sea fisheries research center, Oman 208 Available at - NIO, Goa
  • Fresh marine Available at -
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Poutiers, JM (1998) Bivalves FAO species identification guide for fishery purposes. The living marine resources of the western central Pacific. Volume 1: Seaweeds, corals, bivalves and gastropods FAO, Rome 1 686 pp Available at -
  • Zacharia, PU; Krishnakumar, PK; Dineshbabu, AP; Vijayakumaran, K; Rohit, P; Thomas, S; Sasikumar, G; Kaladharan, P; Durgekar, RN and Mohamed, KS (2008) Species assemblage in the coral reef ecosystem of Netrani Island off Karnataka along the southwest coast of India Journal of the Marine Biological Association of India The Marine Biological Association of India, Cochin, India 50(1) 87-97 Available at - NIO, Goa
  • Animal-World Available at -
  • Appukuttan, KK; Chellam, A; Ramadoss, K; Victor, ACC and Meiyappan, MM (1989) Molluscan resources Bulletin Of Central Marine Fisheries Research Institute CMFRI, Cochin 43 77-92 Available at -
  • Hameed, PS and Somasundaram, SSN (1998) A survey of bivalve molluscs in Gulf of Mannar, India Indian Journal of Fisheries Indian journal of Fisheries for the Indian Council of Agricultural Research, Kochi, India 45(2) 177-181 Available at -

Page last updated on:2012-03-07

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