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Thursday, July 14, 2005

ANIMAL TRACKER

Japanese littleneck clam


* Japanese name: Asari
* Scientific name: Ruditapes philippinarum
* Description: Clams are bivalve mollusks, meaning that they are shellfish, like mussels and oysters. The shells are elongated and pinched together in the center where they join. There are both radial and concentric ribs on the shell. Shells are basically pale beige, but with widely variable black and brown pigmentation. They are orange or violet inside and the bodies are soft. Shells are about 60 mm long.
* Where to find them: In bowls of miso soup all over Japan! Living clams, on the other hand, can be found buried in silt-sand and sand-pebble shores at depths ranging from 1 to 10 meters. Littleneck clams are best found in the summer, when water temperatures are at least 18-20 degrees; and they prefer sheltered shores. Bring a spade to dig them up. Young clams secrete a thread called a byssus, which attaches them to rocks and pebbles.
* Food: Clams feed on algae and plankton, which they filter from the surrounding seawater by extruding a siphon that they use to suck in water. This technique, so useful in natural conditions, means that clams are especially sensitive to pollutants in the water.
* Special features: Littleneck clams are one of the most important shellfish species, and they are cultivated all over Asia. As a result, they are distributed more widely than their natural range. Reproduction takes place externally. A female will spawn her eggs and a male releases sperm over them. There is a planktonic stage which lasts a few days, and then the free-swimming larvae settle down on a hard surface and start to grow a shell. But their marine lifestyle leaves clams vulnerable on two fronts. First, the increasing pollution of coastal waters means that clam meat may often contain high levels of heavy metals, such as cadmium, that are toxic to humans. And with the rise in sea temperatures brought about by global warming, clams are themselves more sensitive to damage by those heavy metals.



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