Biology and Pathogenicity of Benedenia akajin infecting Hatchery-reared Plectropomus leopardus Juveniles

Abstract

Benedenia akajin has recently been described as a new species from cultured coral grouper Plectropomus leopardus. We conducted annual monitoring for the skin monogenean among hatchery-reared P. leopardus juveniles to understand the seasonality of the infections. In addition, growth, development, reproduction, site specificity, and pathogenicity of B. akajin were investigated. The infections were most prominent at a temperature above 25°C and B. akajin was the only capsalid species found in the hatchery-reared P. leopardus juveniles. The parasite took approximately 9 days to reach maturity and had an estimated longevity of approximately 1 month at 26°C. At this temperature, the shortest egg-laying frequency was 131 s, but the oviposition rate was strongly affected by the size of the worm. Most B. akajin individuals were found on the fins of the host. Wounds and lesions were observed on the fins of infected P. leopardus and the host condition factor was negatively correlated with the parasite intensity. These results demonstrated that B. akajin caused decreased growth in cultured P. leopardus juveniles and indicated the needs to control this skin fluke in P. leopardus rearing facilities.