Infestation of gill copepod Lernanthropus latis (Copepoda: Lernanthropidae) and its effect on cage-cultured Asian sea bass Lates calcarifer

摘要

Twenty Asian sea bass Lates calcarifer from a floating cage in Bt. Tambun, Penangwere examined for the presence of parasitic gill copepod, Lernanthropus latis. The prevalenceof L. latis was 100% with the intensity of infection ranging from 1 to 18 parasites per host or3.75 of mean intensity. Female parasites having oblong cephalothorax and egg-strings wereseen mainly on the entire gill of examined Asian sea bass. The infected gill of Asian sea basswas pale and had eccessive mucus production. Under light and scanning electron microscopies(SEM), L. latis was seen grasping or holding tightly to the gill filament using their antenna,maxilla and maxilliped. These structures are characteristically prehensile and uncinate forthe parasite to attach onto the host tissue. The damage was clearly seen under SEM as thehooked end of the antenna was embedded into the gill filament. The parasite also has themandible which is styliform with eight teeth on the inner margin. The pathological effectssuch as erosion, haemorrhages, hyperplasia and necrosis along the secondary lamellae of gillfilaments were seen and more severe at the attachment site. The combined actions of theantenna, maxilla and maxilliped together with the mandible resulted in extensive damage asL. latis attached and fed on the host tissues.