The results described the structure of Longicollum pagrosomi and histopathological characters of the intestine of the red sea bream, Pagrus major, infected with acanthocephalans, using the light and electron microscopes. Among the six samples of P. major, L. pagrosomi was identified in the posterior intestine of five fish samples. Adult L. pagrosomi (total length, 8-27 mm) is divided into the presoma (proboscis, anterior neck, and posterior neck) and metasoma (trunk). The proboscis had vertically arranged hooks (40 μm in length), with ten hooks per row, and the septum was observed between the posterior neck and trunk. The tegument thickness of the proboscis was approximately 15 μm, and it was composed of thin, circular muscle fibers. The outer fibrous membrane was approximately 1 μm, and the connective tissue layer was approximately 35 μm in thickness in the anterior neck. The tegument of the posterior neck enclosed the cephalic ganglion and had longitudinal and vertical muscle fibers, and the tegument thickness was approximately 45 μm. The tegument of the body, which was approximately 1 mm in thickness, was composed primarily of muscle and collagen fibers, and the structure of the tegument was different, depending on the body region. The acanthocephalans had ovaries and oval-shaped eggs with an eggshell (77.5 × 17.1 μm), floating within the body cavity of the trunk. In the infected posterior intestine of P. major, the presoma and the anterior part of the metasoma of L. pagrosomi passed through the intestinal wall and infected the intestinal tissue, perforating the loose connective tissue. In the inflammatory connective tissue, collagen and muscle fibers were fragmented and revealed partial necrosis. Lipid drops and eosinophilic granular cells aggregated in the connective tissue of the tissue capsule. In the vicinity of the acanthocephalan, the mucosal epithelia contained hypertrophied nuclei, and the epithelial layer was collapsed. In an extreme case, the mucosal fold was degenerated because of pressure from the acanthocephalan.

This study was conducted to find out biological response of Manila clam, Ruditapes philippinarum exposed to lead (Pb). Experimental period was four weeks. Experimental groups were composed of one control condition and three lead exposure conditions (0.25, 0.50 and 1.00 mg/l). The results of the study confirmed that lead induces reduction of survival rate and oxygen consumption rate and histopathology of organ structure of the bivalve. Oxygen consumption rate was observed exposure groups lower than control decline by 25%-72%. Histological analysis of organ system illustrated expansion of hemolymph sinus, disappearance of epidermal layer and degeneration of connective tissue layer of the mantle. Also, histological degenerations as epithelial necrosis and hyperplasia of mucous cells are recognized in the gill and it was observed expansion of hemolymph sinus, disruption of epithelial layer, decrease of mucous cell and degeneration of connective tissue layer in the foot. In the digestive diverticulum, it was showed atrophy of basophilic cell and degeneration of epithelial cell in the digestive tubules, and as the concentration of lead increased the accumulation of lipofuscin increased.

Among wild marbled sole, Pleuronectes yokohamae caught in west coastal area, Chungnam, tumor-bearing fish were found. Parasites and pathogenic bacteria were not detected and CPE was not observed. Using the light microscope, the epidermal layer of wild P. yokohamae was significantly thickened compared to the normal skin. The lesion was formed papillary folds. Hypertropical epithelial cells revealed karyolysis, marked nucleolus and cloud swelled cytoplasm. In the epidermal layer of the lesion, X-cell that is characterized by oval and small pale nucleus and prominent nucleolus was observed. Dermal layer had newly formed vessels. The size of mucous cell in the papilloma lesion was significantly increased compared to the normal. In this study, no pathogens were found, so future works for finding cause of the papilloma in the P. yokohamae are needed.