The present authors histopathologically examined renal tumors of two 3-year old rainbow trouts, which were reared in Samegai trout culture station in 1974. The tumors were as large as the size of a hen's egg in the posterior part of the kidney. The tumor consisted of a large number of neoplastic nodules and around which neoplastic islets were scattered in the hematopoietic tissue. The histopathological examination revealed that they were nephroblastoma (known as Wilms' tumor) with two different characteristics. Type I; Neoplastic nodules were composed of a large number of smooth muscle cells in differentiations, well-differentiated renal tubular epithelial cells and a small number of undifferentiated messenchymal cells with argyrophiric fine fibers. Mitotic figures were frequently observed in smooth muscle fibers and messenchymal cells. Type II; Neoplastic nodules were composed of a large number of undifferentiated messenchymal cells and islets of immature renal tubular epithelial cells. Mitotic figures were numerous in both types of cells. Metastatic lesions were not observed in both cases.
Branchiomycosis broke out among the reared Japanese eel (Anguilla japonica) in summer, 1977, in Taiwan. The causative fungus had characteristics similar to B. sanguinis. Fungal hyphae grew in the filamental arteries and lamella capillaries in the gills. Intrahyphal spore-formation was observed in the well grown hyphae. The affected lamellae showed severe circulatory disturbance as dilatation of capillaries, hemorrhages and fibrin deposition. Metastatic lesions with hyphae and spores were observed in the epicardium, but the spleen only spores.
In 1974, 1975 and 1976, nutritional myopathy occurred among cultured young puffers (Fugu rubripes) fed frozen fish meat, in a farm in Kagawa Pref. They were very thin and slender in appearance. One hundred and fifty three diseased puffers were examined histopathologically. This case was characterized by degeneration and necrosis of skeletal muscle fibers, proliferation of connective tissue and appearance of ceroid-laden macrophages in the stroma. It was found that such changes advanced more severely and quickly in erector and depressor muscle tissues than in lateral muscle tissues. In advanced cases most of the skeletal muscle fibers disappeared, and the connective tissue proliferated and ceroid-laden macrophages appeared markedly in the stroma. The lipopigment was deposited in parenchymal cells in the liver. This lipopigment was similar to ceroid in histochemical nature except that the pigment had no acid-fastness. Ceroid-laden macrophages appeared in the spleen, kidney and intestine. The present authors consider the above-mentioned changes closely resemble yellow-fat disease in mammals and aves.
The intraperitoneal absorption properties of Ig purified from coho salmon serum were studied. In all experiments, aliquots of the radiolabeled immunoglobulin were compared in duplicate fish receiving the protein intraperitoneally and intraveneously. This experimental design allowed comparative absorption efficiency and kinetic measurements. The degree and kinetics of absorption were found to be temperature dependent. It was also determined that the monomeric subunit derived from the tetramer was absorbed with lower efficiency over relatively longer periods of time. Absorption results are discussed in terms of their phylogenetic significance.
A Philometra sp. (Nematoda: Philometridae) was first found on the testis and the ovary of the red sea bream, Chrysophrys major, cultured at a farm on the coast of the Amami Island, Kagoshima prefecture. In male fish small masses of several immature female worms were found under the the serous membrane of various parts of the testes, but a large mass of the mature worms was observed only in the connective area of the testes. These observations suggest the worm can develope only in this area. All the large masses of worms were covered with a thin clear membrane originated from the testis serosa. In female fish mature worms were found to be free in the parenchyma of the ovary. The whole body of the worm could not be collected perfectly, because the body wall was very thin and weak against handling and always several worms were entangled complicatedly with each other. Observation was made on the head parts of three fixed specimens. The results were as follows : body length unmeasured; maximum width 0.50-0.57 mm near uterus end and 0.98-1.06 mm behind intestine end; cuticle smooth, 3μ thick; head broadly rounded, without papillae; pharynx 0.98-1.10 mm in long, with bulbus anterior swelling of 0.10-0.12 mm in diameter; anterior ovary partially unobservable; uterus locates 0.33-0.44 mm behind head end, with spherical eggs of 16-18 μ in diameter. The present species differed from P. spari YAMAGUTI, 1961 in not only the habitat of the worm in the host but also the location of the uterus in the gravid female worm. The latter was collected from the swim bladder of the gilthead, Mylio macrocephalus, and its uterus was reported to arise behind the anterior end of the intestine.
A bacteriological examination of internal organs of diseased eels cultured in the Yoshida Region showed that the apparent incidence of eels infected with bacterial pathogens depended on the organs examined. A total of 96 eels carried pathogens such as Aeromonas hydrophila, Edwardsiela tarda and Pseudomonas anguilliseptica in heart (blood), spleen, liver or kidney. The incidence of eels with these bacteria was 77% in heart (blood), 84% in spleen, 89% in liver and 94% in kidney (Table 1).
An epizootic of dermocystidiosis occurred among pond-cultured European eels, Anguilla anguilla for the first time at a fish farm in Shizuoka Prefecture. The fungus was identified as Dermocystidium anguillae which was first reported by SPANGENBERG (1975) in East Germany. The cysts were parasitic in the epithelial and connective tissues of the gills. Attempts were made to culture the parasite on some media, but without success. When the water temperature of tanks with the diseased eels was experimentally raised from 20°C to 30°C, the cysts disappeared from the gills of all the eels within a few days, which suggested that this disease could be cured by warm-water bathing.
From middle July to late August every year, whirling disease caused by the metacercaria of a fluke occurrs in natural anchovies (Engraulis japonica) and cultured yellowtails (Seriola quinqueradiata) in the Tsushima Islands. The only symptom is circular swimming, or whirling, near the sea surface. Fifty diseased anchovies, 100 diseased yellowtails and 10 normal yellowtails were examined parasitologically and histopathologically. All the diseased fishes examined had one or at times two meta cercaria within the interbrain, but it was never detected in the normal fishes. Neither pathogenic bacteria nor protozoa were found in any of the diseased fishes. The metacercaria cyst was white and had the diameter of about 0.8 mm. According to KAMEGAYA et al. (unpublished) this fluke belongs to the genus Galactosmum. Neurons around the metacercaria in the interbrain were found to fall into degeneration or necrosis affected by pressure of the cyst. Because of the abov-mentioned facts, the present authors consider that whirling movement of the infected fishes caused by the metacercaria.