Abstract:
Commonly occurring on a shallow subtidal coarse sand bottom in the northwest Pacific region, the
Jedo Venus clam Leucoma (=Protothaca) jedoensis (Lischke, 1874) is one of the valuable shellfish resources
supporting the local fisheries industry on the south coast of Korea. In this study, we surveyed the pathologic
condition of L. jedoensis from a shallow subtidal sand flat in Gamakman Bay on the south coast using histology
and Ray’s fluid thioglycollate medium (RFTM) assay to diagnose infection by the protozoan pathogen
Perkinsus olseni. In September 2022, a total of 200 clams with shell length (SL) ranging from 29 to 50 mm
were obtained from Gamakman Bay, and each clam was subjected to histology and RFTM assay. Histology
revealed that all clams collected in September were in the resting stage, indicating that L. jedoensis in the study
area completed spawning before September. Perkinsus olseni and unidentified trematode in the sporocysts
stage were observed in histology with a low prevalence of 1.5% and 1%, respectively. Contrary to the
histology, the RFTM assay indicated that 4.5% of the Jedo Venus clams examined in this survey were infected
with P. olseni, with an average infection intensity of 1.1 x 104 cells/g gill, highlighting the presence of P. olseni
in the area. The histology and RFTM assay suggested that P. olseni may not exert a substantial impact on Jedo
Venus clam health, compared to Manila clams, the host of P. olseni occurring in the south coast exhibiting
extremely high levels of P. olseni infection intensities and prevalence.
