Morphology and immunological roles of the three distinct types of hemocytes, hyaline, small granular and large granular cells in black tiger shrimpPenaeus monodonwere studied. The study of functions of these hemocytes in the elimination of injected yeast (Saccharomyces cerevisiae) orVibrio harveyias foreign bodies showed a rapid response against those particles. Together with fixed phagocytes, the blood cells removed the yeast through the process of phagocytosis, nodule formation and encapsulation, which occurred at almost all parts of the body. The injection of the yeast caused a marked reduction in the blood cell counts in the hemolymph during the first 1 h.V. harveyiwas efficiently removed within 3 h after injection. The granular cells (small granular and large granular hemocytes) were the major blood cells that are associated with phenoloxidase activity. The role of hemocytes and fixed phagocytes on defense mechanism in the shrimp were discussed.
Development and growth of the monogenean Neoheterobothrium hirame on Japanese flounder Paralichthys olivaceus were investigated at 15°C, 20°C and 25°C, and production of antibodies against N. hirame was monitored in relation to the development of the parasite. After settlement on the gill filaments, hematin cells in the gut wall of N. hirame were first observed on Day 17, Day 10 and Day 7 post-exposure (PE) of oncomiracidia at 15°C, 20°C and 25°C, respectively. The parasite started to move to the buccal cavity wall from Day 38, Day 24 and Day 24 PE and eggs were observed in the uterus from Day 59, Day 38 and Day 31 PE at each temperature, respectively. Intensity of infection decreased subsequently and infection persisted until Day 122, Day 66 and Day 52 PE, respectively. Antibody titers gradually increased from Day 52 PE at 15°C, while at 20°C and at 25°C, they rapidly increased after a decrease in the intensity and prevalence of the infections was observed. This suggests that the death of the parasite induces a host reaction, resulting in the production of antibodies against N. hirame.
Conventional staining methods for fungal detection are time consuming, technically demanding, and instable dye-affinity in different fungal species, especially in aquatic fungi. In this study, Uvitex 2B [4, 4-BIS (2-di (2-hydroxyethyl) -amino-4 - (3-sulfophenylamino) -1, 3, 5-triazine-6-ylamino) -stilbene-2, 2'-disulfonic acid, sodium salt] was applied to detect fungal elements in paraffin sections of some aquatic animals. As a result, it was found that Uvitex 2B was superior to Gomori's methenamine-silver nitrate Grocott's variation, periodic acid-Schiff reaction and Schmorl's method for staining aquatic fungi in tissue sections. In addition, Uvitex 2B required much shorter time and less specialized skills in the staining procedure than Grocott. Although it has been known that oomycete fungi are difficult to be detected in histopahological sections because of their unstable stainabilities with other staining methods, Uvitex 2B provided excellent results to detect them in tissues of aquatic animals.
A prominent odontoma was found projecting from the maxilla of an elkhorn sculpinAlcichthys elongatus, 27.4 cm in total length, captured in a trap for boreal whelk set offshore from Toyama Bay, the Sea of Japan, in late June, 2002. Microscopic examination of large spherical tumor (29 mm in diameter, 19 mm in depth and 6.5 g in weight) protruding well outside the mouth cavity revealed it to be surrounded by squamous epithelium containing numerous dental tissue masses (imperfect teeth or teeth germ) throughout the stromal tissue. The teeth germ comprised odontoblasts, predentin and calcified dentin. No enamel (substantia adamantia) was demonstrated, although several fragments of calcified trabecular (spongy) bones were encountered. This type of tumor, diagnosed as a compound odontoma, seems to be the first report of such from a teleost from Asian-Oceanic waters. The cause of the tumor is unknown.
Heavy mortalities were observed among pond-culturedPenaeus monodonin the provinces of Bohol, Misamis Occidental, Lanao del Norte and Zamboanga del Sur, Philippines.Vibrio harveyiwas isolated purely from the hepatopancreas and lymphoid organs of affected shrimp and histopathological observations indicated a severe bacterial infection in the shrimp. Majority of the samples gave negative results in the one-step PCR for the detection of white spot syndrome virus (WSSV). However, nested PCR produced amplicons specific for WSSV DNA from most of the shrimp tested. These results suggest that shrimp were infected dually withV. harveyiand WSSV, but the major causative agent of the present mortalities wasV. harveyi.
The efficacy of a vaccine with watersoluble adjuvant (Montanidae IMS 1312) for bacterial coldwater disease was examined in ayuPlecoglossus altivelisunder field conditions. Ayu injected intraperitoneally with formalin-killed bacterin ofFlavobacterium psychrophilummixed with the water-soluble adjuvant were reared in concrete ponds with river water from April to September in 2000 and 2001. Cold water disease occurred spontaneously from the middle of May to the middle of June (2000) and to the middle of July (2001). The mortalities of twice-vaccinated ayu were significantly lower than non-vaccinated ayu in both years and relative percent survivals (RPS) were 33.0% in 2000 and 39.6% in 2001.
Effectiveness of fasting against red sea bream iridoviral disease (RSIVD) in juvenile red sea breamPagrus majorwere evaluated. In an infection experiment, groups which were fasted for 10 or 20 days after challenge showed significantly lower mortalities than a feeding group. In a field trial test, in which a naturally RSIVD-prevailing batch of red sea bream was divided into 2 groups, a fasting group showed significantly lower mortality than a feeding group. These results indicate the effectiveness of fasting after virus infection against RSIVD.