Identification Characteristics:
The shell is disc-shaped, round, and flattened, with a dark brown color. Large individuals have a diameter exceeding 200 mm. The outer surface is typically rough, with numerous ridges and small scales. The hinge is straight, with reduced teeth that are replaced by a black, elastic adhesive mass. The inner surface is smooth and lustrous, exhibiting iridescent nacre. The shell margin is dark brown, and in juvenile individuals, it features numerous dark rays, which disappear as the individual grows beyond 150 mm.
Biology and Ecology:
This species inhabits intertidal to subtidal zones, extending to a depth of 20 meters. It uses byssal threads to attach to substrates such as rocky shores, coral reefs, or other hard surfaces. They often live in groups of 5-10 individuals on a single attachment point.
Distribution:
- Within Vietnam: Ha Long Bay, Cat Ba, Bach Long Vy, Da Nang, Khanh Hoa, Phan Thiet, Hoang Sa Islands, Phu Quoc, Con Dao.
- Worldwide: China, Japan, Philippines.
Value:
The shell’s nacre has value in artistry. It is commonly used in inlay work. The species possesses the capability to produce pearls and can be cultivated.
Conservation Status:
Currently subject to intensive and indiscriminate exploitation, resulting in a decline in population size.
IUCN Red List Status: Vulnerable (VU) A1d C1.
Conservation Measures:
Listed in the Vietnam Red Book (1992). Exploitation needs to be restricted. Research is required for the cultivation and pearl-culturing techniques.