Anchistrotos kojimensis sp. nov. is described based on the adult females recovered in the branchial cavities of Acanthogobius flavimanus (TEMMINCK & SCHLEGEL) from Kojima Bay, Japan. It is the fourth species of parasitic copepods known from this host fish in Japan.
The influence of cell density on viral infectivity titers and interferon production were studied by a plaque and end-point dilution method. The RTG-2 cell line was infected with eel virus European (EVE), infectious pancreatic necrosis virus (IPNV) and infectious hematopoietic necrosis virus (IHNV). The confluent condition of RTG-2 cells was classified into two phases according to the cell density, viz. loosely confluent (6.0 × 104 cells/cm2) and tightly confluent cell sheets (1.2 × 105 cells/cm2). Viral infectivity titers were highest in loosely confluent cell sheets. Virus titers decreased by 50-70% in a plaque method and 90-99% by end-point dilution in tightly confluent cell sheets. Conversely more interferon was produced in tightly rather than loosely confluent cell sheets. We may, therefore, conclude that interferon seems to be a factor contributing to the significant reduction of viral infectivity titers in tightly confluent cell sheets.
An epitheloid morphology cell line designated TO-2 was established from ovary of healthy adult tilapia hybrid(Tilapia mossambica×T.nilotica).Using Leibovitz's L-15 medium with 10% fetal calf serum at 31°C, TO-2 cell line has been passed for 106 times since its initiation in October, 1981.The cells were demonstrated to be free of bacterial, fungal and mycoplasma contaminations. Optimal temperature for TO-2 cell growth was 31°C. The cells are also able to grow at 15 or 24°C. However, in 37°C the cells grew very slowly and eventually died. The growth rate of the cells varied with different serum concentrations in culture media. At a low seeding density (1.6×102-1.6×103/25cm2 flask), the plating efficiency was approximately 12%. Chromosome number at passage level of 80 ranged from 24 to 76 with a modal number of 40. TO-2 cell line is susceptible to EVE, EVA, EVEX and IPNV.
Forty two strains of Vibrio anguillarum were isolated from the spleen of young Ayu in Hamana Lake in 1978. Of the 42 strains 17 were isolated from apparently normal 81 fish captured by small set nets (Kakudate-ami), isolation rate being 21%. The remaining 25 strains were isolated from 25 diseased fish which had been kept in a stocking pond for a few days, isolation rate being 100%. Sixteen strains out of the former 17 strains were classified as serotype B and C, but 24 strains out of the latter 25 strains were serotype A. Twenty five strains were isolated from 34 adult fish which had been cultured in ponds for a few months, and almost all of them were serotype A. These results suggest that the succession of serotype of the bacterium is affected by medication and some other unknown factors during the period of cultivation in ponds.
The drug sensitivity of 56 strains of Vibrio anguillarm, which were isolated from young (normal and diseased) Ayu from Hamana Lake, to nalidixic acid (NA), oxolinic acid (OA), tetracycline (TC), chloramphenicol (CP), nifulpirinol (NP), sulfamonomethoxine (SMM), and sulfadoxine-trimethoprim (SDX-TMP) were examined and expressed as minimal inhibitory concentration (MIC). It is of interest that distinct correlation was found between serotypes and drug sensitivity; Serotype A strains were resistant to NA, OA, and NP, but serotype B and C strains were sensitive to these drugs. As shown in the previous paper, serotype A strains were isolated from diseased adult Ayu from culture ponds, though serotype B and C strains were predominantly isolated from young Ayu caught in Hamana Lake. This change in serotypes was attributed to a selection by certain chemotherapeutics used in culture ponds.
Clavellopsis nodula sp. nov., hitherto reported as C. sargi (KURZ, 1877) from Japanese sea breams, is redescribed and renamed based on the specimens recovered from the gill rakers of Mylio macrocephalus collected in Kojima Bay, Japan.
An infection experiment revealed that the level of secondary bacterial infection increased after parasitization by Argulus coregoni. Fifty juvenile masu trout (Oncorhynchus masou) (30-50 g/fish) and 500 A. coregoni were kept in a container supplied with running water at 13°-15°C contaminated with viable cells of Aeromonas salmonicida, “furunculosis” agent. The other 50 O. masou free from the parasite were used as a control. The fish infected by A. coregoni showed significantly higher mortality than the control fish. The autopsy revealed that external lesions of furunculosis occurred in all parts of the body and were slightly more abundant in the posterior half of the body of both infected and uninfected fishes. In addition, the infected fish had more extensive lesions than the uninfected. However, no definite correlation was detected between the site of the external lesions and that of attachment of A. coregoni.