Inhibitory factor was induced by RTG-2 cell infected with IHN virus. This factor fulfilled the following biological and physicochemical properties. 1) thermostability to heating at 56°C for 30min. 2) acid stability to pH 2 at 4°C for 24hr. 3) nonsedimentation at 100, 000×g at 4°C for 2hr. 4) nondialysis. 5) inactivation by trypsin treatment. 6) cell specific specificity in antiviral effect. 7) wide antiviral spectrum. 8) indirect viral inactivation. Three assays of interferon units were compared. The result indicated that dye uptake method was most sensitive assay, which was 2.1 times as sensitive as plaque reduction method and 2.6 times as sensitive as CPE method. Consequently, it was demonstrated that the factor was interferon.
Two species of metacercariae in the clam Tapes philippinarum (Veneridae) from Lake Hamana were described. One metacercaria was identified as Parvatrema duboisi (DOLLFUS, 1923) BARTOLI, 1974 (Gymnophallidae) and the other was considered as an unreported species belonging to the genus Proctoeces (Fellodistomidae). Morphological characteristics of granules in ceca, excretory vesicle and body cavity of P. duboisi were studied in detail. Histological observations showed that metacercariae of P. duboisi were surrounded with host epithelial tissue at the mantle isthmus. Calcareous deposits around metacercariae were also found at the infection site. P. duboisi was found in 58.3% of 1, 765 clams examined, and its mean intensity reached 3.6 parasites per clam. The level of infection showed variation with no relation to season. The negative binomial distribution was fitted to the frequency distribution of P. duboisi. Proctoeces metacercaria resembled P. ostreae FUJITA, 1925, but its specific identification was uncertain because it was immature. The incidence was very low and only six clams were infected.
The dorsal muscle of sardine(Sardinops melanosticta), frozen as fish diets, was subjected to detection of Streptococcus sp., a pathogen of cultured yellowtail (Seriola quinoueradiata). After the external surface of sardine was disinfected with 70%ethanol, 2-3 g of samples were cut aseptically from the dorsal muscle. The muscle samples were dipped in 70%ethanol and then flamed for disinfecting its surface. Immediately after that, each of the samples were inoculated into nutrient broth, and then incubated for 1-5 days at 25°C. Subsequently, a loopful of the culture was streaked on nutrient agar, and then incubated for 1-2 days at 25°C. Cultures on the plates consisted of various kinds of colonies. On most plates however, pure culture of the objective organisms was observed. As a result, Streptococcus sp. was isolated from all of the 10 sardines sampled. Such remarkable frequency in its detection may be attributed to the enrichment culture using ordinary broth and prolonged incubation. The role of the organism in streptococcal infection-of yellowtail and the cause of its isolation from the sardine muscles as feeds remained to be further clarified in the future.
From June to August in 1981, an epizootic of mycosis occurred among the abalone (Haliotis sieboldii), which were temporarily held in aquaria with circulating sea water adjusted to 15°C by a cooling system, at an abalone storage facility in Sasebo, Nagasaki Prefecture. The typical external symptom of diseased abalones was flat or tubercle-like swelling formed on mantle, epipode and dorsal surface of foot. The mycelium was always observed in the lesions. A fungus was isolated by inoculating materials taken from lesions of diseased abalone onto AMES agar and incubating at 15°C. For the observation of spore discharge, fragments of vegetative hyphae were washed several times with sterile sea water, and then placed in a Petri dish containing sterile sea water. As a result, zoospores formed within the fragment were liberated through the orifice of discharge tube. Encysted spores were spherical, usually 7μm (range of 6 to 10μm) in diameter. The fungus was identified as Haliphthoros milfordensis. The fungus grew at a temperature range of 4.9 to 26.5°C, with optimum of 11.9-24.2°C.
The following results were obtained from investigation about the dynamics of V. anguillarum in process of artificial seedling production of ayu (Plecoglossus altivelis). When ayu reared in sea water, serotype A strains of V. anguillarum were detected from fish and other samples at the first half and serotype C strains were isolated from fish and other samples at the latter half in rearing periods. Continuously, when these fish were transferred to fresh water ponds, there was recognized occurrence of the vibriosis caused by serotye A strains again. Among the serotype A strains were isolated from ayu reared in sea water and fresh water ponds, were demonstrated some differences in biochemical characteristics. Pathogenicity of the isolates was confirmed using ayu and amago (Oncorhynchus rhodurus). Serotype A strains from ayu reaed in sea water ponds were observed excellent growth in 2-3% NaCl concentration at 20°C, but serotype C strains did not. Serotype A strains from ayu reared in fresh water ponds were shown favourable growth in 1% NaCl concentration at 20 c. As V. anguillarum was never detected from both the new sea water and the newly hatched ayu in our survey, the source of V. anguillarum seemed to be rotifer. Drug bathing of rotifers before administrate it to fish considered to be one of the useful control method of the vibriosis in seedling production of ayu.
A brief description was made on Urceolaria sp.(Peritrichia) by using scanning electron microscopy(SEM). It was unexpectedly discovered during the course of histological studies on the buccal funnel of the ammocoete larvae and teeth of the adult lamprey, Lampetra japonica Martens. This is the first record of urceolariid ciliate from the cyclostome in Japan.