Miyagi Prefecture Fisheries Technology Institute

Ishinomaki, Japan

Miyagi Prefecture Fisheries Technology Institute

Ishinomaki, Japan
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Kumagai A.,Miyagi Prefecture Fisheries Technology Institute
Fish Pathology | Year: 2016

Flavobacterium psychrophilum is the causative agent of bacterial cold-water disease (BCWD), inducing severe economic loss in aquaculture worldwide. In Japan, outbreaks of BCWD have often occurred in coho salmon Oncorhynchus kisutch hatcheries and ayu Plecoglossus altivelis farms since the mid-1980s. The disease has been causing serious damages to wild populations of ayu in rivers, and F. psychrophilum has been detected from not only ayu but also other wild fish species. F. psychrophilum in the ovarian fluid can contaminate the surfaces of salmonid eggs and passively enter eggs during water-hardening. The pre-water-hardening disinfection with povidone iodine (50 ppm in isotonic solution, 15 min) of fertilized eggs is a promising method for preventing the transmission of BCWD by eggs. Recently, the disinfection procedure begins to prevail in salmonid hatcheries in Japan. © 2016 The Japanese Society of Fish Pathology.


Hirose E.,University of Ryukyus | Nozawa A.,Ehime University | Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Kitamura S.-I.,Ehime University
Diseases of Aquatic Organisms | Year: 2012

We used morphological and genetic analyses to investigate a pathogenic kinetoplastid isolated from a diseased edible ascidian Halocynthia roretzi with soft tunic syndrome. The morphological characteristics of the kinetoplastid are similar to those in the order Neobodonida in the subclass Metakinetoplastida. However, the presence of unique globular bodies distinguishes this kinetoplastid from the other polykinetoplastic genera (i.e. Cruzella, Dimastigella and Rhynchobodo) in this order. These globular bodies are cytoplasmic inclusions without an outer delimiting membrane and are composed of a homologous granular matrix containing electron-dense bands. A phylogenetic tree based on 18S rRNA gene sequences also indicated that the kinetoplastid belongs to the order Neobodonida, although it forms an independent clade in this order. From these results, we propose a new genus in the order Neobodonida, i.e. Azumiobodo gen. nov., and Azumiobodo hoyamushi as the type species for the genus. © Inter-Research 2012.


Liu Y.-G.,Tohoku National Fisheries Research Institute | Kurokawa T.,Tohoku National Fisheries Research Institute | Sekino M.,Tohoku National Fisheries Research Institute | Sekino M.,Japan National Research Institute of Fisheries Science | And 2 more authors.
Comparative Biochemistry and Physiology - Part D: Genomics and Proteomics | Year: 2013

The complete mitochondrial (mt) genome of the ark shell Scapharca broughtonii was determined using long PCR and a genome walking sequencing strategy with genus-specific primers. The S. broughtonii mt genome (GenBank accession number AB729113) contained 12 protein-coding genes (the atp8 gene is missing, as in most bivalves), 2 ribosomal RNA genes, and 42 transfer tRNA genes, in a length of 46,985 nucleotides for the size of mtDNA with only one copy of the heteroplasmic tandem repeat (HTR) unit. Moreover the S. broughtonii mt genome shows size variation; these genomes ranged in size from about 47 kb to about 50 kb because of variation in the number of repeat sequences in the non-coding region. The mt-genome of S. broughtonii is, to date, the longest reported metazoan mtDNA sequence. Sequence duplication in non-coding region and the formation of HTR arrays were two of the factors responsible for the ultra-large size of this mt genome. All the tRNA genes were found within the S. broughtonii mt genome, unlike the other bivalves usually lacking one or more tRNA genes. Twelve additional specimens were used to analyze the patterns of tandem repeat arrays by PCR amplification and agarose electrophoresis. Each of the 12 specimens displayed extensive heteroplasmy and had 8-10 length variants. The motifs of the HTR arrays are about 353-362 bp and the number of repeats ranges from 1 to 11. © 2012 Elsevier Inc.


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries | Ito H.,Miyagi Prefecture Fisheries Technology Institute | Sasaki R.,Miyagi Prefectural Fisheries Cooperative Association
Diseases of Aquatic Organisms | Year: 2013

The occurrence of soft tunic syndrome in wild populations of the ascidian Halocynthia roretzi was monitored by diving at 5 to 6 sites in Miyagi Prefecture in Japan in summer 2010 and 2011. These sites were located at varying distances from farming sites at which the disease had previously been detected. All dead ascidians were collected, and their tunics were examined for Azumiobodo hoyamushi, the causative agent of soft tunic syndrome, using 18S rRNA PCR. In both years, <1% of wild ascidians we observed (18 out of 2100 in 2010, and 30 out of 3100 in 2011) were dead. The flagellates were only detected in 8 out of 18 dead ascidians from 3 sites in 2010, and 4 out of 30 from 2 sites in 2011. Healthy ascidians were successfully experimentally infected with the disease by immersing tunic samples from diseased wild ascidians into the rearing water. When apparently healthy ascidians collected from the wild population were reared for 40 d using pathogen-free water, the tunics of some ascidians became softened. The flagellates were detected in these individuals, which were diagnosed with soft tunic syndrome. Our results suggest that soft tunic syndrome affects the wild population of ascidians in Japan. © Inter-Research 2013.


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Nawat A.,Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries Experimental Station
Fish Pathology | Year: 2011

We measured the concentration of F. psychrophilum in the ovarian fluid and milt of six species of salmonids that were collected from freshwater fish farms in Japan. We detected the bacteria in 39 of 61 groups of female fish (544 of 3,276 fish) and 21 of 42 groups of male fish (248 of 1,434 fish). The concentration of F. psychrophilum ranged from 10 to 10 7.7 CFU/mL (mean 10 2.0 CFU/mL) in the ovarian fluid and from 10 to 10 4.5 CFU/mL (mean 10 2.1 CFU/mL) in the milt. Our data suggest that the bacteria are widely distributed, and are present at high levels, throughout Japan © 2011 The Japanese Society of Fish Pathology.


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Nawata A.,Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries Experimental Station
Fish Pathology | Year: 2011

We evaluated the occurrence of intra-ovum infection with Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease (BCWD) and rainbow trout fry syndrome (RTFS), in the eggs of six salmonid species in Japan. Flavobacterium psychrophilum was isolated from four eggs in one of 13 lots of eyed eggs (999 eggs) imported from the United States. In contrast, the bacterium was not isolated from 28 lots (1,680 eggs) or 61 lots (3,693 eggs) of domestically produced unfertilized or eyed eggs, respectively. Our results indicate there is a low likelihood of intra-ovum infection in cultured salmonids in Japan © 2011 The Japanese Society of Fish Pathology.


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Kamaishi T.,Japan National Research Institute of Fisheries And Environment of Inland Sea
Fish Pathology | Year: 2013

PCR assays were developed for the rapid and sensitive detection of Azumiobodo hoyamushi, the protistan pathogen that causes soft tunic syndrome in the cultured ascidian Halocynthia roretzi. Two sets of A. hoyamushi-specific primers based on the 18S rRNA and b -tubulin gene sequences, respectively, of the flagellate were designed and validated for the detection of A. hoyamushi. In both PCR assays, the flagellate genes were detected in diseased ascidians, but not in apparently healthy ones. When DNA were extracted from flagellate suspensions obtained from infected tunics, the detection limits of the PCR assays using primers for the 18S rRNA and b -tubulin were 3.4 × 10 cells/mL and 3.4 × 102 cells/mL, respectively. Even at the early stage of infection when the slight clinical signs were observed only in the siphons, A. hoyamushi was detected from the affected tissue using 18S rRNA PCR, but not b -tubulin PCR. Thus, the 18S rRNA PCR is a rapid, sensitive and specific assay for diagnosing soft tunic syndrome. © 2013 The Japanese Society of Fish Pathology.


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Nawata A.,Miyagi Prefecture Fisheries Technology Institute
Fish Pathology | Year: 2010

We evaluated the efficacy of povidone-iodine treatments in preventing vertical transmission of Flavobacterium psychrophilum in the eggs of masu salmon Oncorhynchus masou, Japanese char Salvelinus pluvius, coho salmon O. kisutch and rainbow trout O. mykiss. When newly spawned eggs were immersion-challenged with F. psychrophilum (> 10 9 CFU/mL) and subsequently disinfected with povidone-iodine (50 ppm in PBS, 15 min) prior to fertilization, the pathogen was not detected in the contents of the eggs. Without this pre-fertilization disinfection with povidone-iodine, however, procedures such as water-hardening of immersion-challenged eggs in povidone-iodine (50-100 ppm in water) and rinsing of the F. psychrophilum-contaminated eggs with PBS were insufficient to control the intraovum infection. In a separate experiment using coho salmon eggs challenged with F. psychrophilum, pre-fertilization disinfection was effective to prevent bacterial cold-water disease in the produced fry. Surface disinfection of unfertilized eggs immediately after spawning is thus essential to prevent vertical transmission of F. psychrophilum. © 2010 The Japanese Society of Fish Pathology.


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Nawata A.,Miyagi Prefecture Fisheries Technology Institute
Fish Pathology | Year: 2010

The mode of intra-ovum infection by Flavobacterium psychrophilum, which causes bacterial cold-water disease and rainbow trout fry syndrome, was investigated in eggs of rainbow trout Oncorhynchus mykiss. When newly spawned unfertilized eggs were immersion-challenged with F. psychrophilum at concentrations of 107 CFU/mL or higher and subsequently inseminated and water-hardened, the bacteria were detected in the egg contents. The infection rate in eggs was related to the bacterial concentration in a dose-dependent manner. When mature female rainbow trout were intraperitoneally injected with F. psychrophilum (3.3 × 109 CFU/fish) 5-9 days prior to ovulation, intra-ovum infection was found in eggs spawned from the fish showing heavy contamination of the bacterium in the ovarian fluid (> 10 6 CFU/mL). These results indicate that F. psychrophilum can contaminate the surface of eggs in ovarian fluid and enter eggs during water-hardening. Live bacterial counts within experimentally infected eggs and immuno-staining observations on the eggs suggested that F. psychrophilum passively entered into the eggs (< 10 CFU/egg) and subsequently grew to over 107 CFU/egg in the perivitelline space by the eyed egg stage. Multiplication of the bacterium in the perivitelline space did not affect the survival of eggs. © 2010 The Japanese Society of Fish Pathology.


Tanabe T.,Miyagi Prefecture Fisheries Technology Institute
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2012

In Miyagi Prefecture, the moon snail Euspira fortunei seems to have been brought from other prefectures or countries such as China or North Korea together with seeds of the clam Ruditapes philippinarum. This species is a predatory gastropod that drills holes in the shell of a prey and causes severe of damage for the fishery of R. philippinarum. The drilled holes produced by predatory gastropods are uniquely preserved on the prey shells and represent important evidence on the behavior of predators. In this study, the drilled-hole diameters were signi ficantly correlated with predator size. The author collected drilled shells of dead R. philippinarum of Mangokuura and Torinoumi in Miyagi Prefecture, and calculated the E. fortunei shell height using the relationship between the drilled-hole diameter and shell height of E. fortunei. The prey sizes were correlated with calculated predator sizes in both areas, and the highest frequency of the predator-prey coefficient of shell length of prey (mm)/ calculated shell height of predator (mm), was 0.7-0.8. These results indicate size-selective predation of E. fortunei.

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