The causative organism of fish mycobacteriosis in ornamental fish (goldfish, Carassius auratu and red eyed tetra, Moenkhausia sanctaefilomenae) in Malaysia was characterized by examining biochemical and physiological properties. The organism formed tiny white colonies in less than three days at 30°C on Bacto Lowenstein Medium in complete darkness, but become yellow after exposure to light (photochromogenic). The isolate was an acid-fast, weakly Gram positive rod and the guanine plus cytosine (% G+C) was 62.6. It was confirmed that the isolate belonged to the genus Mycobacterium. The isolate differed in many characteristics from the reference strains of M. chelonei subsp. chelonei and M. chelonei subsp. abscessus, as well as the rapidly growing, photochromogenic M. parafortuitum and M. vaccae cited in the Bergey's Manual of Systematic Bacteriology vol. 2 (1986).
Desquamative enteritis, due to a Vibrio and externally displays white gut, occurred among larval Japanese flounder (Paralichthys olivaceus) reared at the Hiroshima Prefectural Fisheries Experimental Station in 1986 and the Mie Prefectural Fisheries Experimental Station in 1988. Vibrio sp. INFL group that has been confirmed to be a causative bacterium of this disease by experimental infection (MASUMURA et al., 1989) was the dominant isolate from diseased fish. In this study an indirect immunofluorescent technique and a histopathological study were performed to reveal the invasiveness of Vibrio sp. INFL group into intestinal tissues. Slight infectious lesions occurred in the mucosae of posterior part of intestine and the rectum. These lesions showed separation of affected mucosal cells with invasions of numbers of Vibrio sp. INFL group that were revealed by the specific fluorescence. Extended intestinal lesions involved the posterior half of intestine and the rectum. They showed marked bacterial multiplication in mucosae and the underlying tunica propria, and extensively slouphed mucosae, indicating that the histological characteristic was desquamative enteritis. The invasive bacteria were revealed to be Vibrio sp. INFL group by the specific fluorescence. Other visceral organs were spared of the bacterial invasions. The damage of intestine and rectum would induce fish mortalities.
Effects of seawater acclimation on juvenile salmonids infected with gill monogeneans, Tetraonchus awakurai and T. oncorhynchi, and systemic fungus, Ichthyophonus hoferi, were investigated. In the acclimation test from freshwater to 50 % seawater, the serum sodium level of Tetraonchusparasitized amago salmon smolts (Oncorhynchus rhodurus) increased during the first 24 hours but decreased afterward and reached the same level as in marine fishes (ca. 150 mM) after 4 days, indicating the infection has no negative effect against the seawater adaptation. The two species of Tetraonchus died when exposed to 4.5% NaCl for 10 min. or 2.5% NaCl for 60 min. This result indicated that they are eradicated in seawater during the course of seawater acclimation. In Ichthyophpnus-infected juvenile rainbow trout (Oncorhynchus mykiss), on the contrary, the serum sodium level increased rapidly and exceeded 200 mM with 95 % mortality after transfer to 100% seawater for 4 days. Apparently, Ichthyophouns was not affected by exposure of trout to seawater or the increment of the host NaCl level.
The pili of Flavobacterium branchiophila ATCC 35035 were purified and characterized. After mechanical detachment from the bacterial cells, the pili were concentrated by ultrafiltration. The purification of the pili was carried out by ion-exchange chromatography on DEAE-cellulose. By electron microscopy, the purified pili were observed to be filaments measureing approximately 4 nm by 1μm The molecular weight of the protein subunits of the purified pili was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. One protein subunit had a molecular weight of 23, 000 dalton, and the other faintly stained protein might be a dimer of the objective molecule. The purified pilus subunit was rich in aspartic acid and glutamic acid, alanine and glycine, but poor in histidine and methionine. Ultraviolet absorption spectrum of the purified pili showed a maximum absorption at 276 nm, and the extinction coefficient was calculated to be 41.0. In serological analysis, four strains of F. branchiophila produced a single common precipitin line against rabbit anti-pili serum. These results suggest that the pili are relatively homogeneous and a common structural component among the strains of F. branchiophila.
The aerobic bacterial flora of larval swimming crabs (Zoea-I to Crab-I) cultured in three hatcheries were investigated in relation to the microflora of rearing pond water and diets. The external and internal bacterial counts of the crab on ZoBell's 2216 e agar ranged from 102 to 104 and 101 to 104 CFU/animal, respectively. The number of the bacterial counts increased as the developmental stages progressed. In respect of constitution, Vibrio and Pseudomonas predominated both in external and internal bacterial flora. The total bacterial counts for rearing pond water, live diets (rotifer and brine shrimp) and minced/artificial foods ranged 104105, 106108, and 103105 CFU/ml or g, respectively. The bacterial flora of rearing pond water and live diets consisted of mainly Vibrio and Pseudomonas, while from the minced food and artificial food only Pseudomonas was predominantly isolated.
Myxosporean cysts were found in the mesentery, brain, liver, spleen, and pancreas of four mullets, Mugil cephalus, with spinal curvature, lordo-scoliosis, caught in a bay of Mie Prefecture, Japan. The cysts were most abundantly and frequently observed in the mesentery and brain. Although the cysts were distributed in various parts of the brain such as the 4th ventricle, the cavity of the optic tectum, the surface of the olfactory lobes and bulbs and the optic lobes, the 4th ventricle was the most common site of infection in all 4 fish examined. The cysts were spherical, about 1 mm in diameter. Dimensions (μm) of fresh spores : length, 10.5-12.5; width, 9.0-11.0; thickness, 6.0-7.5; polar capsule : length, 3.5-5.0; width, 2.5-3.5;polar filament : length, 19-39.Spores of the species were distinctly different from those of the other members of the genus Myxobolus on the basis of their shape, structure and dimensions examined by light and scanning electron micrography. Thus, we propose a new species Myxobolus spinacurvatura sp. n. for the present species.