Giant clam

Figure 1. Histogram of measurements of molar U/Ca ratio in a number of samples of reef-building corals and one giant clam sample (after Edwards 1988). Also indicated is the U/Ca ratio of seawater. This illustrates the point that corals do not fractionate U from Ca by large amounts when they make their skeletons. U/Ca ratios of corals are similar to values from inorganically precipitated marine aragonite. Mollusks along with most other biogenic minerals exclude uranium. Note that the horizontal axis is on a log scale and that the U/Ca ratio of the clam is almost 5 orders of magnitude lower than that of the corals. This difference is the fundamental reason why there are difficulties with uranium-series dating of mollusks.

Soria-Dengg, S. and D. Ochavillo. 1990. Comparative toxicities of trace metals on embryos of the giant clam, Tridacna derasa. Asian Mar. Biol. 7 161-166. 

Fankboner, P. V. (1971). Intracellular digestion of symbiotic zooxanthellae by host amoebocytes in giant clams (Bivalvia Tridacnidae) with a note on the nutritional role of the hypertrophied siphonal epidermis, Biol. Bull., 141, 222-234. 

Hayden H, Blomster J, Maggs C, Silva P, Stanhope M, Waaland J (2003) Linnaeus was right all along Ulva and Enteromorpha are not distinct genera. Eur J Phycol 38 277-294 Hill RW, Dacey JWH, Edward A (2000) Dimethylsulfoniopropionate in giant clams (Tridacnidae). Biol Bull 199 108-115... 

Tridacna dam Poisoning. Giant clams of the species Tridacna maxima, commonly eaten in French Pol)mesia, may sometimes give rise to digestive disorders and serious disturbances of the nervous system, such as paresthesia, lack of motor coordination, ataxia, and tremor. Such on outbreak occurred at Bora-Bora in the Society Islands in 1964 (37). About 30 persons were affected and there were two deaths. Numerous domestic animals which had eaten the remnants... 

The kidney of the giant clam Tridacna maxima yielded an arsenic-containing sugar sulfate (213), the structure of which was determined by X-ray crystallography [218]. 

Resting Membrane Potential A variety of unusual invertebrates, including giant clams, mussels, and polychaete worms, live on the fringes of hydrothermal vents on the ocean bottom, where the temperature is 60 °C. 

Some adult invertebrates in tropical areas have relatively high MAA concentrations in external surfaces. Holothuroids preferentially accumulate MAAs in the epidermis, giant clams have highest concentrations of MAAs in the outermost layers of siphonal mantle tissue (more than four times the concentrations in subsurface mantle layers), sea hares have high MAA levels in skin, and ascidian tunics have higher MAA concentrations in the surface cells than in basal dermal lay-ers 102,152 154 jn coraiSj e upper exposed surface of colonies can have five-fold higher UV absorption than the less irradiated vertical faces.155 These topical distribution patterns reinforce the premise that MAAs have a photoprotective function. 

Molluscs vary greatly in size, ranging from minute creatures of less than 1 millimetre across, to giant clams. Most, but not all, have shells. 

Giant clams can reach almost a metre in diameter and are very solid with a porcelain-like inner layer. Mounted on plinths they have been used in churches as benetiers (holy water fonts), and examples exist in stately homes and palaces where they have been used purely for decoration. 

Belda, C. A., Lucas, J. S., and YeUowlees, D. (1993). Nutrient limiation in the giant clam-zooxantheUae symbiosis Effects of nutrient supplements on growth of symbiotic partners. Mar. Biol. 117, 655-664. 

The tetramethylarsonium ion 53, arsenobetain 54, and arsenocholine 55 were detected in the soft tissues of both the pearl-free and the pearl-containing pearl oysters Pincdata fucata [162]. More than 20 years ago, arsenic-containing sugars 56 and 58 have been isolated from the kidney of the giant clam, Tridacna maxima [163]. Water-soluble arsenic species were determined in the kidney of the Tridacna derasa [164]. A total of fifteen organoarsenic species were identified, and 13 of these possessed... 

L.A. Wilkens (1984). Ultraviolet sensitivity in hyperpolarizing photoreceptors of the giant clam Tridacna. Nature, 309,446-448. 

Ambariyanto and Hoegh-Guldberg, O. (1999) Net uptake of dissolved free amino acids by the giant clam, Tridacna maxima alternative sources of energy and nitrogen Coral Reefs, 18, 91-96. 

Masuzawa, T., Handa, N., Kitagawa, H. and Kusakabe, M. (1992) Sulfate reduction using methane in sediments beneath a bathyal cold seep giant clam community off Hatsushima Island, Sagami Bay, Japan. Earth and Planetary Science Letters, 110, 39-50. 

KA Francesconi, JS Edmonds, RV Stick. Arsenic compounds from the kidney of the giant clam Tridacna maxima. Isolation and identification of an arsenic-containing nucleoside. J Chem Soc Perkin Trans 1 1349-1357, 1992. 

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