Abstract
We described a cryptic population of the Portuguese oyster Crassostrea angulata (Lamarck, 1819) identified from the coast of Shikoku Island, Japan. At the same location, we also confirmed the distribution of a recently recognized oyster species, C. dianbaiensis Xia, Wu, Xiao & Yu, 2014. As a diagnostic tool for species identification, we used the nucleotide sequences of three mitochondrial genes. These sequences were capable of reliably discriminating each of the above two species from their most closely related species: C. angulata from C. gigas (Thunberg, 1793), and C. dianbaiensis from C. bilineata (Röding, 1798). Our finding of a previously unrecognized distribution of these species provides important information to help promote the conservation of species diversity of Japanese oysters.
