Papers by Tomoyoshi YOSHINAGA
Diseases of Aquatic Organisms, Jul 7, 2008
The protozoan parasite Marteilioides chungmuensis causes irregular enlargement of the ovary in th... more The protozoan parasite Marteilioides chungmuensis causes irregular enlargement of the ovary in the Pacific oyster Crassostrea gigas. The parasite invades the oyster through the epithelial tissue of the labial palp, replicates in the connective tissue, and then moves to the gonad, producing spores inside the oocytes. In this study the seasonality and invasion period of the parasite into the host was investigated over a 1 yr cycle. Uninfected 1 and 0 yr old (spat) oysters were placed in an epizootic area every month from July 2004 to July 2005 and September 2005 to March 2006, respectively, and left for 1 mo. Labial palps and gonad were sampled monthly and examined for infection by nested PCR and histological observations. Prevalence of infection detected by PCR was 70% or higher from August to October, but declined sharply in November and reached 7% or lower from February to April. To explain the low detection rate in winter, 1 yr old uninfected oysters were placed in an epizootic area in winter (water temperature: 8 to 10°C) for 2 wk and then transferred to M. chungmuensis-free seawater at 24°C. Although prevalence of infection was ca. 7% before transfer to heated seawater, levels of 87% were detected after 1 wk. After a 3 wk exposure to heated seawater, parasites were found in host oocytes by histological observation. It was concluded that the low prevalence in winter was due to insufficient replication of M. chungmuensis at low seawater temperatures, resulting in levels not detectable by nested PCR, and not to the absence of invasion.
Parasitology, Aug 11, 2023
Identification of glycine betaine as a host-derived molecule required for the vegetative prolifer... more Identification of glycine betaine as a host-derived molecule required for the vegetative proliferation of the protozoan parasite Perkinsus olseni.
Fish Pathology, 2015
イカリムシ L e r n a e a c y p r i n a c e aは世界中に広く分布す る淡水魚の寄生虫である。多数のイカリムシが寄生した 養殖魚では，その固着部位における炎症や粘液... more イカリムシ L e r n a e a c y p r i n a c e aは世界中に広く分布す る淡水魚の寄生虫である。多数のイカリムシが寄生した 養殖魚では，その固着部位における炎症や粘液過剰分泌 を伴った壊死や潰瘍の形成，およびそれら病変部からの 細菌や真菌などの二次感染により，衰弱して死亡するこ とがある。このため，我が国におけるイカリムシの研究 は主に養殖魚を対象にして行われ，多くの知見が得られ ている(笠原， 1 9 6 2 )が，天然魚におけるイカリムシの 寄生生態に関する知見は乏しい。 庄内川は岐阜県と愛知県を流れ，伊勢湾に注ぐ本川流 路延長 9 6 k mの一級河川で，近年では環境の改善に伴っ て天然アユ P l e c o g l o s s u s a l t i v e l i sの遡上が見られるよう s h P a t h o l o g y , 5 0 ( 2 ) , 8 1 -8 4 , 2 0 1 5 . 6 © 2 0 1 5 T h e J a p a n e s e S o c i e t y o f F i s h P a t h o l o g y 1 三重大学大学院生物資源学研究科 2 東京大学大学院農学生命科学研究科 * Co r r e s p o n d i n g a u t h o r E -ma i l : i s s h i k i @b i o . mi e -u . a c . j p 庄内川の天然アユおよびその他数種の 魚類におけるイカリムシ L e r n a e a c y p r i n a c e aの 寄生状況 好峯 侑 1 ・一色 正 1 * ・間野静雄 1 K a y L wi n T u n 2 ・良永知義 2 (2 0 1 4 年1 2 月1 0 日受付) Oc c u r r e n c e o f L e r n a e a c y p r i n a c e a ( Co p e p o d a ) i n Wi l d A y u P l e c o g l o s s u s a l t i v e l i s a n d S e v e r a l Ot h e r F i s h e s i n t h e S h o n a i Ri v e r , J a p a n Y u Y o s h i mi n e 1 , T a d a s h i I s s h i k i 1 * , S h i z u o A i n o 1 , K a y L wi n T u n 2 a n d T o mo y o s h i Y o s h i n a g a 2 1 Gr a d u a t e S c h o o l o f Bi o r e s o u r c e s , Mi e Un i v e r s i t y , Mi e 5 1 4 -8 5 0 7 , J a p a n 2 Gr a d u a t e S c h o o l o f A g r i c u l t u r a l a n d L i f e S c i e n c e s , T h e Un i v e r s i t y o f T o k y o , T o k y o 1 1 3 -8 6 5 7 , J a p a n ( Re c e i v e d De c e mb e r 1 0 , 2 0 1 4 )
Fish Pathology, 2001
Southern flounder Paralichthys lethostigma distributed in the Atlantic waters of North America an... more Southern flounder Paralichthys lethostigma distributed in the Atlantic waters of North America and Japanese flounder P. olivaceus were challenged with the monogenean Neoheterobothrium hirame, known so far as a parasite of Japanese flounder. Mature worms were obtained from the challenged flounders, both Japanese flounder and southern flounder, although
Fish Pathology, 2000
Recently,severe anemia of unknown etiology has been observed frequently in both wild and cultured... more Recently,severe anemia of unknown etiology has been observed frequently in both wild and cultured Japanese flounder, Paralicthys olivaceus, in Japan. Hematological and parasito logical examinations and histopathlogical examinations on the hematopoietic organs were carried out in anemic flounder. The anemia was hematologically characterized by the appearance of many immature erythrocytes and abnormal staining in the cytoplasm (vacuolation or weak staining) of erythrocytes. Histopathologically, deposition of hemosiderin or necrosis was rarely observed in the kidney or spleen of the anemic flounder. The blood-feeding monogenean,Neoheterobothrium hirame, was observed at high prevalences in flounder groups in which many anemic fish were contained. These observations suggest that the anemia was caused by the hematophagia by the parasite.
Fish Pathology, 2003
Leucocyte types involved in tne cellular response of Japanese flounder Paralichthys olivaceus aga... more Leucocyte types involved in tne cellular response of Japanese flounder Paralichthys olivaceus against the monogenean Neoheterobothrium hirame were identified. With electron microscopy, peripheral blood leucocytes (PBL) of Japanese flounder could be classified into four types: lymphocytes, thrombocytes, monocytes and granulocytes. Granulocytes were positive for acid phosphatase and peroxidase activities, and stained with Sudan black B. In fish infected with N. hirame, the ratios of granulocytes and monocytes significantly increased in the PBL composition. Infiltration of monocytes/macrophages and granulocytes, and cells having large electron-dense granules (DGC) was observed in the infection sites. These cells were often ob served adhering to the tegument of N. hirame. Monocytes/macrophages showed particularly higher adherent ability to N. hirame than the other leucocytes under in vitro and in vivo conditions. We conclude that monocytes/macrophages, granulocytes and DGC are major effector cells in the defense of the flounder against N. hirame.
Fish Pathology, 2002
One hundred spat of Crassostrea gigas obtained from a coastal area in north-eastern Japan were ex... more One hundred spat of Crassostrea gigas obtained from a coastal area in north-eastern Japan were examined for the protistan parasite Haplosporidium nelsoni. Haplosporidium-like plasmodia were histologically observed in two spat and positively reacted with a H. nelsoni-specific probe in in situ hybridization. Four spat including the two spat in which the plasmodia were found showed positive reaction in PCR analysis for the detection of H. nelsoni. The small subunit ribosomal RNA sequence amplified from the spat was virtually identical (99.7%) to the sequence of H. nelsoni previously reported. These results demonstrate that H. nelsoni is distributed in Japan.
NIPPON SUISAN GAKKAISHI, 2014
Outbreaks of infection with Ostreid herpesvirus 1 micro variant (OsHV 1 mVar) causing mortalitie... more Outbreaks of infection with Ostreid herpesvirus 1 micro variant (OsHV 1 mVar) causing mortalities in Pa- ciˆc oyster were reported from Europe and Oceania. The Ministry of Agriculture, Forestry and Fisheries issued warnings of the disease to prefectural ˆsheries divisions and requested them to give the warnings to people and organizations concerned. However, the ‰ow of the warnings was not investigated and it was unclear whether the warnings were actually received by those concerned. We investigated the ‰ow of the warnings by interviews and questionnaire, and found that the warnings were mainly issued to oyster farmers via ˆsheries cooperatives and
NIPPON SUISAN GAKKAISHI, 2005
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Papers by Tomoyoshi YOSHINAGA