Oyster genome reveals a shellfish character

Chinese researchers have cracked open the genetic code of the Pacific oyster, shedding light on an ancient creature that plays a key role in the ecosystem, a study published on Wednesday showed. A peek into the genome of Crassostrea gigas points to a treasure trove of genes to help the mollusc cope with environmental stress, from varying salinity and desiccation to exposure to bacteria and toxic metals. Eighty-eight genes alone are devoted to heat shock, a particular risk for oysters, given that their lives are governed by tide levels. The genome should unlock new knowledge about the evolution of molluscs and the risks they face from global warming, say the authors, led by Guofan Zhang of the Chinese Academy of Sciences in Qingdao. Man-made carbon emissions, from the burning of coal, oil and gas, are partly absorbed by the oceans and thus add to their acidity, which weakens molluscs' protective calcium shells. These greenhouse gases also add to global warming, another threat for shellfish in shallow waters. "Molluscs have vital roles in the functioning of marine, freshwater and terrestrial ecosystems," says the study, published in the British journal Nature. "(They) have major effects on humans, primarily as food sources but also as sources as dyes, decorative pearls and shells, vectors of parasites and biofouling or destructive agents." Previous genomes of molluscs have included the pearl oyster, Pinctada fucata, whose draft code was published in February this year by Japanese scientists.