Press Release

June 4, 2012

Incorporated Administrative Agency, Fisheries Research Agency

Fast and simple methods for discriminating live Kumamoto oysters from Pacific oysters developed!

  • Kumamoto oysters can be discriminated in 1.5 hr from a pinch of ligament with forceps.
  • Oysters can also be discriminated undamaged by excrement analysis.

Crassostrea sikamea, known as shikame in Japan and “Kumamoto oyster” outside Japan, is small and sweet, and is a common oyster in oyster bars, etc. The species lives in the beaches along the Ariake Sea and the Yatsushiro Sea together with other oyster species such as Pacific oyster (C. gigas). Because Kumamoto and Pacific oysters are morphologically alike, they need to be discriminated by gene analysis. However, conventional genetic methods are too complicated and costly, and thus the development of simple and fast methods has been hoped for.

The Fisheries Research Agency developed technologies for discriminating the oysters in not more than one and a half hours, sharply reducing the time from 8 hours in the conventional method without special equipment or knowledge. The new method just involves excising a minute amount of the ligament muscle and analyzing the genes and does not require specific devices or knowledge. It also succeeded in discriminating the oysters in a non-destructive manner, which involves just analyzing the excrement. The methods will be useful for collecting and surveying oyster seeds, developing technologies for artificial cultivation of Kumamoto oyster, and ensuring correct food labeling.

Kumamoto oysters (Crassostrea sikamea, top) produced in the USA and
Pacific oysters (Crassostrea gigas, bottom) produced in Japan