Perkinsus spp. infections between cultured and wild oysters Crassostrea hongkongensis and Saccostrea mordax

Human activities have altered the growth and development of oysters, thereby affecting the reproduction of parasites within the oysters and promoting the spread and transmission of parasites. We evaluated the effects of human activities on Perkinsus spp. infection in Crassostrea hongkongensis and Saccostrea mordax. We collected the oyster samples (Six wild oyster populations and four cultured oyster populations) at the eight sites along the South China coast, then we analyzed the Perkinsus spp. prevalence and abundance difference between the cultured and wild conditions. The results show that the mean prevalence of Perkinsus spp. in cultured C. hongkongensis was (61.25±13.30)%, not significantly different with wild C. hongkongensis, but both were significantly higher than that in wild S. mordax, which had an prevalence of (13.75±5.45)%. Among different sites, the prevalence of Perkinsus spp. in cultured C. hongkongensis was significantly different with wild C. hongkongensis, but was not significantly different between wild C. hongkongensis and S. mordax. The mean abundance of Perkinsus spp. in wild C. hongkongensis was (1 144.79±295.85) cells·gram⁻¹, not significantly different with wild S. mordax. However, the mean abundance of Perkinsus spp. in both wild C. hongkongensis and S. mordax was significantly lower than that in cultured C. hongkongensis, which had an abundance of (14 668.08±8 379.21) cells·gram⁻¹. Among different sites, there were no significant differences in the abundance of Perkinsus spp. among cultured C. hongkongensis, wild C. hongkongensis and wild S. mordax. The common practice of C. hongkongensis transplantation between regions had facilitated the transmission of Perkinsus spp. among different sites. High contrasts between cultured and wild environment lead to their significant abundance difference of Perkinsus spp. It is first reported that S. mordax is infected with Perkinsus spp., which indicates the widespread transmission and strong infectivity of Perkinsus spp. S. mordax has a unique attachment life style, which reduces its' infection risk of Perkinsus spp. Wild C. hongkongensis has a tendency of low abundance of Perkinsus spp. infection, so its population is suitable for breeding of seedlings, which reduces vertical and horizontal transmission risk of Perkinsus spp.