Diagnosis of Marteilioides chungmuensis in wild Pacific oyster Crassostrea gigas using a histology and nested PCR

Abstract

Marteilioides chungmuensis, a protozoan parasite, infects the oocytes of cultured Pacific oysters Crassostrea gigas in Korea and Japan. Most studies of Marteilioides infection in Korea was mainly focused on cultured oysters using a conventional histology, whereas there was no attempt to examine the health assessment in wild populations. In the present study, we investigated the infection of Marteilioides in wild oysters collected from Gwangyang Bay and Masan Bay on southern coast of Korea, 2009 using a histology and nested PCR. Histology revealed that oysters from three of 8 sites in Masan Bay and two of 7 sites in Gwangyang Bay were infected with Marteilioides and the prevalence of parasite in both bays ranged from 3.3-26.7% and 3.3-6.6%, respectively. All infected oysters were female and egg size of infected oyster also significantly smaller than that of normal oysters (p<0.05). Furthermore, parasite infection of oysters from two bays using Marteilioides specific primer was confirmed. Female and male oysters in both bays were found to be infected with M. chungmuensis and prevalence was much higher 10-83.3% and 16.6-86.6% than the histology. In particular, the prevalence of parasite in most of male oysters in both bays showed a high infection compared to females. Sequences of PCR product were 99.9-100% identical to the 18S rDNA of M. chungmuensis reported in Japan. This is the first reporentional histology, whereas there was no attempt to examine the health assessment in wild populations. In the present study, we investigated the infection of Marteilioides in wild oysters collected from Gwangyang Bay and Masan Bay on southern coast of Korea, 2009 using a histology and nested PCR. Histology revealed that oysters from three of 8 sites in Masan Bay and two of 7 sites in Gwangyang Bay were infected with Marteilioides and the prevalence of parasite in both bays ranged from 3.3-26.7% and 3.3-6.6%, respectively. All infected oysters