1. 1977年4月から1979年2月にわたって,養殖コイとキンギョの寄生虫調査を行ない,鰓弁からDactylogyrus属に属する6種を得た。2. 上記の属の種類は,キンギョから,D. dulkeiti,.D. formosus, D. anchoratus, D. baueri, D. intermedius, D. vastatorの6種,コイからD.anchoratus1種であり,D.vastatorを除く5種は日本における初報告種である。3. 採集した標本について種の分類のkeyである後固着盤と交接器のキチン質構造を記載した。D.dulkeitiとD.formosusでは,内部形態も観察した。4. 現在では,Dactylogyrusは,キンギョからは上記6種, コイからはD.anchoratus,D. extensus, D.minutusの3種が日本から知られている。
A large amount of red seabream Pagulus major (Temminck and Schlegel) larvae, 8.0-11.0 mm in total length, was killed by the parasitism of larval treamtode during a course of experimental culture in large scale. Many young numerous larvae trematode were found in the alimentary canal, and a few one in the urinary bladder, ureter and renal tubule of the diseased larvae of red seabream. The infection was presumably caused by the active feeding of red seabream larvae on the larval trematode libreated from their first intermediate host, top shell (Batillus cornutus).
Some bacterial diseases such as pseudotuberculosis (Pasteurella piscicida infection)and streptococcal infection(Streptococcus spp. infection)have been prevailing among cultured populations of yellowtail(Seriola quinqueradiata) in Japan. In the course of diagnostic works about bacterial infections of yellowtail in Tokushima Prefecture from 1976 to 1978, it was found that an additional bacterial disease, i.e. vibriosis, had been causing considerable mortalities for those three years in addition to the above-mentioned two diseases. The occurrences of the three diseases or the three pathogens in 1977 was demonstrated in a table, where it was shown that the vibriosis took place in the young fish (Body weight 3.7-42.5g) from late May to early July. The external sign of the vibriosis was characterized by opaque or congested eyes, eroded fins, darkened body color, and hemorrhagic or necrotic lesions on body surface and musculature. Vibrio sp. was isolated from these diseased fish, and submitted to characterization tests, agglutination tests with anti-V. anguillarum sera, and a pathogenicity test with healthy yellowtail. Putting all the results together., the etiological agent of the disease was identified as Vibrio anguillarum. This is the first record of V. anguillarum infection in yellowtail, though another vibriosis, the causative agent of which was reported as Vibrio sp. by KUSUDA (1965), has been known.