Crassostrea talonata, a new threat to native oyster (Bivalvia: Ostreidae) culture in the Southwest Atlantic

Abstract Genetic analyses of oyster seeds collected from settlement plates (in southeast Brazil Santa Catarina, N  = 207) and from marsh plants (Argentina, Samborombon Bay, N = 20) revealed that most seeds did not belong to any of the oyster species recorded for the Atlantic. Phylogenetic analyses based on mitochondrial (Cytochrome c Oxidase subunit I and large ribosomal subunit) and nuclear (ribosomal Internal Transcribed Spacer 2) sequences positioned that species in the Asian oyster cluster of Crassostrea , suggesting an invasive origin and identifying the species as C. talonata , a species described for China and also recently found in Peru. The predominance of this species in cultivation settlement plates indicates that it outcompetes C. gasar , native of the South-Atlantic, making it a nuisance species for oyster cultivation. Since specimens of C. talonata have been found from the mouth of the Amazon to the coast of Argentina, it is likely that the species has a large ecological plasticity and possibly a strong invasive capacity, making it a major threat to oyster culture in the area. This is the first record of C. talonata for the Atlantic.