Depth range based on 8 specimens in 3 taxa.
Water temperature and chemistry ranges based on 7 samples.

Environmental ranges
  Depth range (m): 1.5 - 12
  Temperature range (°C): 26.645 - 29.241
  Nitrate (umol/L): 0.047 - 0.806
  Salinity (PPS): 33.706 - 35.216
  Oxygen (ml/l): 4.502 - 4.692
  Phosphate (umol/l): 0.087 - 0.165
  Silicate (umol/l): 1.047 - 3.088

Graphical representation

Depth range (m): 1.5 - 12

Temperature range (°C): 26.645 - 29.241

Nitrate (umol/L): 0.047 - 0.806

Salinity (PPS): 33.706 - 35.216

Oxygen (ml/l): 4.502 - 4.692

Phosphate (umol/l): 0.087 - 0.165

Silicate (umol/l): 1.047 - 3.088
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.


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General Ecology

DMS in the odor landscape of the sea

Dimethyl Sulfide or DMS is present throughout the ocean(1). It’s an important odor component of many fish and shellfish, including clams, mussels, oysters, scallops, crabs and shrimp(2-9). Where does it come from? Usually from the marine plants they feed on.

Many species of plants and algae produce DMS, but not all species produce significant amounts of it. Nearly all of these are marine, and they tend to be in closely related groups with other DMS-producers, including Chlorophyte (green) seaweeds, the Dinophyceae in the dinoflagellates, and some members of the Chrysophyceae and the Bacillariophyceae (two classes of diatoms). Other large groups, like cyanobacteria and freshwater algae, tend not to produce DMS. (10,11)

Why do these groups produce DMS? In algae, most researchers believe a related chemical, DMSP, is used by the algae for osmoregulation- by ensuring the ion concentration inside their cells stays fairly close to the salinity in the seawater outside, they prevent osmotic shock. Otherwise, after a sudden exposure to fresh water (rain at the sea surface, for instance) cells could swell up and explode. In vascular plants, like marsh grasses and sugar cane, it’s not clear what DMS is used for. (12,13)

Freshly harvested shellfish can smell like DMS because DMSP has accumulated in their tissue from the algae in their diet. Some animals, including giant Tridacna clams and the intertidal flatworm Convoluta roscoffensis, harbor symbiotic algae in their tissues, which produce DMSP; this may not be important to their symbioses, but for Tridacna, the high DMS levels can be a problem for marketing the clams to human consumers. After death, DMSP begins to break down into DMS. A little DMS creates a pleasant flavor, but high concentrations offend the human palate.(2,14)

Not all grazers retain DMS in their tissues, though. At sea, DMS is released when zooplankton feed on algae. It’s been shown in the marine copepods Labidocera aestiva and Centropages hamatus feeding on the dinoflagellate Gymnodinium nelson that nearly all the DMS in the consumed algae is quickly released during feeding and digestion.(15) This has a disadvantage for the grazing zooplankton. Marine predators, like procellariiform seabirds, harbor seals, penguins, whale sharks, cod, and coral reef fishes like brown chromis, Creole wrasse and boga, can use the smell of DMS to locate zooplankton to feed on. (8,16,17)

It’s not easy to measure how much DMS is released from the Ocean into the air every year. Recent estimates suggest 13-37 Teragrams, or 1.3-3.7 billion kilograms. This accounts for about half the natural transport of Sulfur into the atmosphere, is the conveyor belt by which Sulfur cycles from the ocean back to land. In the atmosphere, DMS is oxidized into several compounds that serve as Cloud Condensation Nuclei (CCN). The presence of CCN in the air determines when and where clouds form, which affects not only the Water cycle, but the reflection of sunlight away from the Earth. This is why climate scientists believe DMS plays an important role in regulating the Earth’s climate. (12,18)

  • 1) BATES, T. S., J. D. Cline, R. H. Gammon, and S. R. Kelly-Hansen. 1987. Regional and seasonal variations in the flux of oceanic dimethylsulfide to the atmosphere. J. Geophys. Res.92: 2930- 2938
  • 10) Malin, G., Kirst, G.O. 1997. Algal Production of Dimethyl Sulfide and its Atmospheric Role. J. Phycol., 33:889-896
  • 11) Keller, M.D., Bellows, W.K., Guillard, R.L. 1989. Dimethyl Sulfide Production in Marine Phytoplankton. Biogenic Sulfur in the Environment. Chapter 11, pp 167–182. ACS Symposium Series, Vol. 393. ISBN13: 9780841216129eISBN: 9780841212442.
  • 12) Yoch, D.C. 2002. Dimethylsulfoniopropionate: Its Sources, Role in the Marine Food Web, and Biological Degradation to Dimethylsulfide. Appl Environ Microbiol., 68(12):5804–5815.
  • 13) Otte ML, Wilson G, Morris JT, Moran BM. 2004. Dimethylsulphoniopropionate (DMSP) and related compounds in higher plants. J Exp Bot., 55(404):1919-25
  • 14) Van Bergeijk, S.A., Stal, L.J. 2001. Dimethylsulfonopropionate and dimethylsulfide in the marine flatworm Convoluta roscoffensis and its algal symbiont. Marine Biology, 138:209-216
  • 15) Dacey , J.W.H. and Stuart G. Wakeham. 1986. Oceanic Dimethylsulfide: Production during Zooplankton Grazing on Phytoplankton. Science, 233( 4770):1314-1316
  • 16) Nevitt, G. A., Veit, R. R. & Kareiva, P. (1995) Dimethyl Sulphide as a Foraging Cue for Antarctic Procellariiform Seabirds. Nature 376, 680-682.
  • 17) Debose, J.L., Lema, S.C., & Nevitt, G.A. (2008). Dimethylsulfionoproprianate as a foraging cue for reef fishes. Science, 319, 1356.
  • 18) Charlson, R.J., Lovelock, J.E., Andraea, M.O., Warren, S.G. 1987. Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate. Nature, 326:655-661
  • 2) Hill, RW, Dacey, JW and A Edward. 2000. Dimethylsulfoniopropionate in giant clams (Tridacnidae). The Biological Bulletin, 199(2):108-115
  • 3) Brooke, R.O., Mendelsohn, J.M., King, F.J. 1968. Significance of Dimethyl Sulfide to the Odor of Soft-Shell Clams. Journal of the Fisheries Research Board of Canada, 25:(11) 2453-2460
  • 4) Linder, M., Ackman, R.G. 2002. Volatile Compounds Recovered by Solid-Phase Microextraction from Fresh Adductor Muscle and Total Lipids of Sea Scallop (Placopecten magellanicus) from Georges Bank (Nova Scotia). Journal of Food Science, 67(6): 2032–2037
  • 5) Le Guen, S., Prost, C., Demaimay, M. 2000. Critical Comparison of Three Olfactometric Methods for the Identification of the Most Potent Odorants in Cooked Mussels (Mytilus edulis). J. Agric. Food Chem., 48(4): 1307–1314
  • 6) Piveteau, F., Le Guen, S., Gandemer, G., Baud, J.P., Prost, C., Demaimay, M. 2000. Aroma of Fresh Oysters Crassostrea gigas: Composition and Aroma Notes. J. Agric. Food Chem., 48(10): 4851–4857
  • 7) Tanchotikul, U., Hsieh, T.C.Y. 2006. Analysis of Volatile Flavor Components in Steamed Rangia Clam by Dynamic Headspace Sampling and Simultaneous Distillation and Extraction. Journal of Food Science, 56(2): 327–331
  • 8) Ellingsen, O.F., Doving, K.B. 1986. Chemical fractionation of shrimp extracts inducing bottom food search behavior in cod (Gadus morhua L.). J. Chem. Ecol., 12(1): 155-168
  • 9) Sarnoski, P.J., O’Keefe, S.F., Jahncke, M.L., Mallikarjunan, P., Flick, G. 2010. Analysis of crab meat volatiles as possible spoilage indicators for blue crab (Callinectes sapidus) meat by gas chromatography–mass spectrometry. Food Chemistry, 122(3):930–935
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:485
Specimens with Sequences:465
Specimens with Barcodes:153
Species With Barcodes:7
Public Records:444
Public Species:6
Public BINs:5
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Source: Barcode of Life Data Systems (BOLD)


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Barcode data

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Tridacna is a genus of large saltwater clams, marine bivalve mollusks in the subfamily Tridacninae, the giant clams. They have heavy shells, fluted with 4 to 6 folds. The mantle is brightly coloured. They inhabit shallow waters of coral reefs in warm seas of the Indo-Pacific region.[2] These clams are popular in marine aquaria, and in some areas, such as the Philippines, members of the genus are farmed for the marine aquarium trade. They live in symbiosis with photosynthetic algae (zooxanthellae). Some species are eaten by humans.

Systematics and phylogeny[edit]

The genus contains two subgenera and the following species:[3][4]

Subgenus Tridacna (Tridacna)

Subgenus Tridacna (Chametrachea)

An alternative older classification recognises a third subgenus Persikima containing T. derasa and T. mbalavuana.[5] Recent biochemical studies have suggested that there may exist morphologically indistinct cryptic species.[2][6]


Compared to other clams, the soft mantle that secretes the shell is greatly expanded. The clams even have small lens-like structures called ocelli through which light penetrates.[7]

Ecology and behaviour[edit]

Tridacna clams are common inhabitants of Indo-Pacific coral reef benthic communities in shallower waters.[8] They live in symbiosis with photosynthetic dinoflagellate algae (Symbiodinium) that grow in the mantle tissues.[9] Light penetrates the mantle through small lens-like structures called ocelli.[7] They are sessile in adulthood. By day, the clams spread out their mantle so that the algae receive the sunlight they need to photosynthesize, whereas the colour pigments protect the clam against excessive light and UV radiation. Adult clams get most (70-100%) of their nutrients from the algae and the rest from filter feeding.[10] When disturbed, the clam closes its shell. The popular opinion that they pose danger to divers who get trapped or injured between the closing sharp-edged shell is not very real, as the closing reaction is quite slow. Their large size and easy accessibility has caused overfishing and collapse of the natural stocks in many places and extirpation in some of the species.[11] They are being sustainably farmed in some areas,[12] both for the seafood market in some Asian countries and for the aquarium trade.[13]

Tridacna clams can produce large white pearls with an undulating, porcelain-like surface,[14] which may be described as "non-nacreous pearls". The "Pearl of Lao Tzu", also known as the "Pearl of Allah", is the world's largest pearl weighing 6.4 kilogrammes; it was said to have been found inside a Tridacna gigas by a Filipino diver in 1934.[15][16]

Artistic use[edit]

Over a hundred examples of carved Tridacna shells have been found in archaeological expeditions from Italy to the Near East. Similar in artistic style, they were probably produced in the mid-seventh century, made or distributed from the southern coast of Phoenicia. The backs and interior perimeters of the shells show animal, human, and floral motifs, while the interiors typically show recumbent sphinxes. The umbo of the shell is in the shape of a human female or bird's head. They were probably used to store eye cosmetics.[17]



  1. ^ "The Paleobiology Database". Retrieved 2012-05-20. 
  2. ^ a b Huelsken, T., Keyse, J., Liggins, L., Penny, S., Treml, E.A., Riginos, C. (2013) A Novel Widespread Cryptic Species and Phylogeographic Patterns within Several Giant Clam Species (Cardiidae: Tridacna) from the Indo-Pacific Ocean. PLoS ONE, DOI: 10.1371/journal.pone.0080858.
  3. ^ WoRMS. (2009). Tridacna. Accessed through the World Register of Marine Species at on 2009-01-08.
  4. ^ Schneider, J.A.,and O´Foighil, D. Phylogeny of Giant Clams (Cardiidae: Tridacninae) Based on Partial Mitochondrial 16S rDNA Gene Sequences. Molecular Phylogenetics and Evolution Vol. 13, No. 1, October, pp. 59–66, 1999
  5. ^ Benzie,J.A.H. and Williams,S.T. Phylogenetic relationships among giant clam species (Mollusca: Tridacnidae) determined by protein electrophoresis. Marine Biology (1998) 132: 123±133
  6. ^ Mohamed, N.M. et al., Molecular Genetic Analyses of Giant Clam (Tridacna sp.) Populations in the Northern Red Sea. Asian Journal of Biochemistry, 1 (4): 338-342 (2006)
  7. ^ a b Murphy 2002, p. 25
  8. ^ Rosewater, J., The Family Tridacnidae in the Indo-Pacific. Indo-Pacific Mollusca, 1:347-408. 1965
  9. ^ Jantzen, C., et al. Photosynthetic performance of giant clams, Tridacna maxima and T. squamosa, Red Sea. Marine Biology (2008) 155:211–221
  10. ^ Klumpp,D.W., Lucas,J.S., Nutritional ecology of the giant clams Tridacna tevoroa and T. derasa from Tonga: influence of light on filter-feeding and photosynthesis. Mar. Ecol. Prog. Ser. Vol 107, 1994
  11. ^ J.W. Copland and J.S. Lucas, (Eds.), Giant Clams in Asia and the Pacific Vol. 9, Australian Center for International Agricultural Research, Canberra(1988).
  12. ^ Murphy 2002, p. 28
  13. ^ Advanced Aquarist - Aquarium Invertebrates: A Trip to an Indonesian Coral and Clam Farm
  14. ^ CIBJO (2007) THE PEARL BOOK:: Natural, Cultured & Imitation Pearls: Terminology & Classification - 5.216. Tridacna gigas (p. 28)
  15. ^ Natural History - PICKS FROM THE PAST: NOVEMBER 1939 - The Pearl of Allah
  16. ^ Prager, Ellen (2011), Sex, Drugs, and Sea Slime: The Oceans' Oddest Creatures and Why They Matter, The University of Chicago Press, ISBN 978-0-226-67872-6 (pp. 64-64)
  17. ^ Markoe, Glenn. Phoenicians. British Museum Press (2000).


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