Effects of larval trematode parasitism on the reproductive capacity of Manila clam Ruditapes philippinarum in a sandy-mud tidal flat on the west coast of Korea

Gonad intrusion of the larval trematodes often results in substantial damage to reproductive capacity some economically important marine bivalves. Such detrimental impacts trematode infection are observed Manila clam Ruditapes philippinarum coastal Yellow Sea, although effects on host’s reproduction poorly understood. Accordingly, this study attempts understand parasitism using histology. Of 1,255 adult clams collected early June from a tidal flat west coast Korea, 68 individuals (5.4%) were infected by three different trematodes, including Cercaria tapidis , pectinata and Parvatrema duboisi . Histology revealed that uninfected late developing or ripe stage, exhibiting fully developed gametes expended follicles. In contrast, showed retarded gonad maturation. Some those remained sexually indifferent (13/68 clams) (9/68 clams). We categorized level into (0), light (1), moderate (2), heavy (3), very (4), according area sporocysts occupying histology section. The image analysis indicated approximately 50% “heavy” “very heavy” conditions, they occupied 16.7% 26.9% total cross-section area, respectively. nonparametric Kruskal–Wallis’s test post-hoc Tukey’s condition index (CI) significantly lower than clams. conclusion, about 5.4% population we estimated 32.4% might fail reproduce during spawning period due severe infection.