Record of the endangered flat oyster, Ostrea denselamellosa(Mollusca: Bivalvia: Ostreidae) in Osaka Bay, Japan

: In Japan, the flat oyster Ostrea denselamellosa Lischke, 1869 （ Mollusca: Bivalvia: Ostreidae ） has been known to occur along the coasts of Mutsu Bay south of the East China Sea. This species was commonly fished, especially in the Seto Inland Sea and Mikawa Bay until the 1980s. However, this natural resource has since deteriorated, and consequently, there has been no record of O. denselamellosa in Osaka Bay for several decades. In the present study, we sampled 11 Ostrea specimens collected with the help of an anchor dredge in Osaka Bay, and identified them as O. denselamellosa based on mito chondrial DNA barcoding. To our knowledge, the present study is the first record of O. denselamellosa from Osaka Bay after the latest recorded catch in 1980. Moreover, our specimens with various shell sizes implied that O. denselamellosa successfully reproduces in Osaka Bay.