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Mizuno S, Urawa S, Miyamoto M, Hatakeyama M, Koide N, Ueda H. Experimental evidence on prevention of infection by the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon using ultraviolet disinfection of rearing water. J Fish Dis 2019; 42:129-140. [PMID: 30397926 DOI: 10.1111/jfd.12920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 10/01/2018] [Accepted: 10/04/2018] [Indexed: 06/08/2023]
Abstract
In northern Japan, juvenile chum salmon Oncorhynchus keta (Walbaum) are released from hatcheries to enhance the fishery resource. Infections with ectoparasitic protozoans, particularly the flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae, occasionally cause severe mortality among hatchery-reared juveniles. This study examined the susceptibility of the two parasites to wide-ranging UV irradiation (experiment 1) and then investigated whether UV disinfection of the rearing water using a commercial device was useful for preventing infections among juveniles in a small-scale rearing system over a 28-day period (experiment 2). In experiment 1, parasite mortality reached 100% with UV irradiation doses of ≥9.60 × 105 μW s/cm2 for I. salmonis and ≥8.40 × 105 μW s/cm2 for T. truttae. In experiment 2, disinfection of the rearing water at a UV irradiation dose of 2.2 × 106 μW s/cm2 succeeded in complete prevention of both parasites in the juvenile salmon. These results elucidate the minimum dose of UV irradiation for inactivation of I. salmonis and T. truttae, and demonstrate the usefulness of water disinfection using a commercial UV irradiation device to prevent infections by these parasites in hatchery-reared juvenile chum salmon.
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Affiliation(s)
- Shinya Mizuno
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Shigehiko Urawa
- Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Sapporo, Japan
| | - Mahito Miyamoto
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Makoto Hatakeyama
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Nobuhisa Koide
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Hiroshi Ueda
- Field Science Center for Northern Biosphere, Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
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Mizuno S, Urawa S, Miyamoto M, Hatakeyama M, Sasaki Y, Koide N, Tada S, Ueda H. Effects of dietary supplementation with oregano essential oil on prevention of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon Oncorhynchus keta. J Fish Biol 2018; 93:528-539. [PMID: 29938795 DOI: 10.1111/jfb.13681] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 06/01/2018] [Indexed: 06/08/2023]
Abstract
The present study performed three experiments to establish a practical prevention strategy for the ectoparasitic flagellate Ichthyobodo salmonis and ciliate Trichodina truttae in hatchery-reared juvenile chum salmon Oncorhynchus keta using dietary supplementation with oregano essential oil. Experiment 1 showed that a diet supplemented for 3 weeks with 0.02% oregano essential oil significantly prevented infection with I. salmonis and T. truttae in juveniles reared in small tanks. Experiment 2, in outdoor hatchery ponds, demonstrated that the oregano treatment completely prevented I. salmonis infection for 52 days and T. truttae infection for 38 days. Oregano-treated juvenile mortality attributable to infection with these protozoans also decreased to 7.6% of control juvenile mortality, confirming the utility of this treatment in cultured O. keta. Physiological analyses of the oregano-treated juveniles elucidated the treatment's safety in relation to their metabolism, osmoregulation, natural immunity and olfactory responses and also detected carvacrol (a major component of oregano essential oil which shows antimicrobial activity) on the skin. In experiment 3, exposure of the two protozoans to oregano essential oil revealed a weak antiparasitic action on the body surface of the juvenile O. keta. The overall results demonstrate that dietary oregano supplementation is a practical prevention strategy for I. salmonis and T. truttae in hatchery-reared juvenile O. keta and suggest the possibility that its anti-parasitic action is attributable to a component of the oil that emerges onto the skin of the body of the fish.
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Affiliation(s)
- Shinya Mizuno
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Shigehiko Urawa
- Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Sapporo, Japan
| | - Mahito Miyamoto
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Makoto Hatakeyama
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Yoshitaka Sasaki
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | - Nobuhisa Koide
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Japan
| | | | - Hiroshi Ueda
- Hokkaido Aquaculture Promotion Corporation, Sapporo, Japan
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Mizuno S, Urawa S, Miyamoto M, Saneyoshi H, Hatakeyama M, Koide N, Ueda H. Epizootiology of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae on wild chum salmon Oncorhynchus keta. Dis Aquat Organ 2017; 126:99-109. [PMID: 29044040 DOI: 10.3354/dao03162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Infestations of the ectoparasitic flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae have caused acute mortalities of hatchery-reared juvenile chum salmon Oncorhynchus keta in Hokkaido, northern Japan. This study examined the epizootiology of I. salmonis and T. truttae on wild chum salmon as a possible infection source of the 2 parasitic protozoans in hatcheries. Infestations by both ectoparasites were detected on freshwater-adapted adult and juvenile chum salmon in all 4 rivers examined. This is the first study of an anadromous Pacific salmonid to report infestation of I. salmonis and T. truttae in adults returning for spawning. Among the marine-inhabiting phase of chum salmon, infestation with I. salmonis, but not T. truttae, was observed on adults and juveniles. The 2 protozoans were experimentally transmitted at the same time from wild to hatchery-reared chum salmon juveniles, and caused a high rate of mortality in the hatchery fish. In freshwater, the proliferation rate of T. truttae was greater than that of I. salmonis. These observations show that the euryhaline ectoparasite I. salmonis can infest chum salmon throughout their life cycle, in both river and ocean habitats, whereas T. truttae is able to infest these salmonids only in freshwater. Furthermore, wild chum salmon were shown to be a potential infestation source for both T. truttae and I. salmonis in hatchery fish.
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Affiliation(s)
- Shinya Mizuno
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, Eniwa, Hokkaido 061-1433, Japan
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Myers K, Irvine J, Logerwell E, Urawa S, Naydenko S, Zavolokin A, Davis N. Pacific Salmon and Steelhead: Life in a Changing Winter Ocean. ACTA ACUST UNITED AC 2016. [DOI: 10.23849/npafcb6/113.138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Azumaya T, Sato S, Urawa S, Nagasawa T. Potential Role of the Magnetic Field on Homing in Chum Salmon (Oncorhynchus keta) Tracked from the Open Sea to Coastal Japan. ACTA ACUST UNITED AC 2016. [DOI: 10.23849/npafcb6/235.241] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Urawa S, Irvine J, Kim JK, Volk E, Zavolokin A, Azumaya T, Beacham T, Bugaev A, Farley E, Guyon J, Kim SG, Kishi M, Klovach N, Koval M, Lee DH, Naydenko S, Oxman D, Saito T, Sato S, Saunders M, Temnykh O, Tompkins A, Trudel M, Volobuev V, Warheit K, Davis N. Forecasting Pacific Salmon Production in a Changing Climate: A Review of the 2011–2015 NPAFC Science Plan. ACTA ACUST UNITED AC 2016. [DOI: 10.23849/npafcb6/501.534] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Yokoyama H, Urawa S, Grabner D, Shirakashi S. Henneguya cartilaginis n. sp. (Myxozoa: Myxosporea) in the head cartilage of masu salmon Oncorhynchus masou masou. Parasitol Int 2012; 61:594-8. [PMID: 22664475 DOI: 10.1016/j.parint.2012.05.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/22/2012] [Accepted: 05/24/2012] [Indexed: 11/17/2022]
Abstract
Henneguya cartilaginis n. sp. (Myxozoa: Myxosporea) is described from wild masu salmon Oncorhynchus masou masou in Hokkaido, Japan. H. cartilaginis n. sp. produced white cysts, up to 3mm in size, in the head of masu salmon. Infected fish exhibited cranial protrusion due to the cysts. Spores (11.4 × 8.6 μm) of H. cartilaginis n. sp. were egg-shaped with the posterior end more pointed and possessed two caudal appendages (34.2 μm average length). Histological observations revealed that large plasmodia possessing fine fibrous pseudopodia on the surface developed in the head cartilage. H. cartilaginis n. sp. resembles H. cerebralis, which was described from the cranial cartilage of Kosogol grayling Thymallus nigrescens in Mongolia. However, they were distinguishable by spore morphology. Molecular analysis of the 18S rDNA sequences indicated that H. cartilaginis n. sp. was most closely related to Henneguya zschokkei, H. nuesslini and H. salminicola of salmonid fish, with genetic similarities of 95.3%, 95.1% and 93.9%, respectively. Based on these differences in spore morphology, molecular data, the site of infection and geographical distribution, the present species is considered to be a new species.
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Affiliation(s)
- Hiroshi Yokoyama
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
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Urawa S, Freeman MA, Johnson SC, Jones SRM, Yokoyama H. Geographical variation in spore morphology, gene sequences, and host specificity of Myxobolus arcticus (Myxozoa) infecting salmonid nerve tissues. Dis Aquat Organ 2011; 96:229-237. [PMID: 22132501 DOI: 10.3354/dao02398] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Myxobolus arcticus Pugachev and Khokhlov, 1979 is a freshwater myxosporean parasite infecting the nerve tissues of salmonid fishes throughout the Pacific region of Far East Asia and North America. The principal fish host is sockeye salmon Oncorhynchus nerka in North America and masu salmon O. masou in Japan. Actinospores of M. arcticus were isolated from the lumbriculid oligochaetes Lumbriculus variegatus and Stylodrilus heringianus in Japan and Canada, respectively. Morphological comparisons indicated that Japanese actinospores from L. variegatus have significantly shorter caudal projections than Canadian isolates from S. heringianus, whereas the corresponding myxospores are indistinguishable. Transmission experiments showed that sockeye salmon were rarely susceptible to the Japanese actinospores, while masu salmon are highly susceptible to this parasite. Sequences of 4560 base pairs of the ribosomal RNA (rRNA) gene, including small subunit (SSU) and internal transcribed spacer (ITS) regions, from Japanese and Canadian isolates had a high similarity over 99.9%, suggesting that they may be conspecific. However, the biological data indicate that they are at least distinct strains. M. arcticus may be geographically isolated due to the specific homing migration of the anadromous fish hosts and has specialized its morphology and host selection for its local environment in the ongoing process of differentiation, potentially leading to speciation.
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Affiliation(s)
- Shigehiko Urawa
- Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Toyohira-ku, Sapporo 062-0922, Japan.
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Yu JN, Azuma N, Yoon M, Brykov V, Urawa S, Nagata M, Jin DH, Abe S. Population genetic structure and phylogeography of masu salmon (Oncorhynchus masou masou) inferred from mitochondrial and microsatellite DNA analyses. Zoolog Sci 2010; 27:375-85. [PMID: 20443684 DOI: 10.2108/zsj.27.375] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The population genetic structure and phylogeography of masu salmon were investigated by using variation in the mitochondrial NADH dehydrogenase subunit 5 gene (ND5) and six polymorphic microsatellite loci among a total of 895 fish representing 18 populations collected from Japan (9), Russia (7), and Korea (2) from 2000 to 2008. An analysis of ND5 nucleotide sequences revealed 22 variable sites in about 560 bp in the 5' half of the gene, which defined 20 haplotypes, including some associated with geographical regions. Haplotype and nucleotide diversities were greater in the populations in Japan and Korea than in those in Russia, indicating greater genetic diversity in the Japanese and Korean populations than in the Russian populations. All the microsatellite loci examined showed a high level of variation, but the expected heterozygosity indicated a similar level of genetic diversity among the populations of the three regions, contrary to the results for ND5. However, AMOVA and pairwise population F (ST) estimates for both ND5 and the microsatellite markers indicated a similar pattern of moderate genetic differentiation among populations of the three regions, and large population groups on the coasts of the Sea of Japan, Sea of Okhotsk, and Pacific Ocean in the Far East. From a mismatch distribution analysis and neutrality test, the observed genetic structure appears to have been influenced primarily by bottlenecks during glacial periods and population expansions during interglacial periods in the late Pleistocene.
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Affiliation(s)
- Jeong-Nam Yu
- Division of Marine Biociences, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan
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Moriya S, Sato S, Azumaya T, Suzuki O, Urawa S, Urano A, Abe S. Genetic stock identification of chum salmon in the Bering Sea and North Pacific Ocean using mitochondrial DNA microarray. Mar Biotechnol (NY) 2007; 9:179-91. [PMID: 17186428 DOI: 10.1007/s10126-006-6079-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Accepted: 09/23/2006] [Indexed: 05/13/2023]
Abstract
A newly developed DNA microarray was applied to identify mitochondrial (mt) DNA haplotypes of more than 2200 chum salmon in the Bering Sea and North Pacific Ocean in September 2002 and also 2003, when the majority of maturing fish were migrating toward their natal river. The distribution of haplotypes occurring in Asian and North American fish in the surveyed area was similar in the 2 years. A conditional maximum likelihood method for estimation of stock compositions indicated that the Japanese stocks were distributed mainly in the north central Bering Sea, whereas the Russian stocks were mainly in the western Bering Sea. The North American stocks were abundant in the North Pacific Ocean around the Aleutian Islands. These results indicate that the Asian and North American stocks of chum salmon are nonrandomly distributed in the Bering Sea and the North Pacific Ocean, and further the oligonuleotide DNA microarray developed by us has a high potential for identification of stocks among mixed ocean aggregates of high-seas chum salmon.
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Affiliation(s)
- Shogo Moriya
- Research and Development Center, Nisshinbo Industries, Inc., 1-2-3, Onodai, Midori-ku, Chiba, 267-0056, Japan.
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Yokoyama H, Kim JH, Urawa S. Differences in host selection of actinospores of two myxosporeans, Myxobolus arcticus and Thelohanellus hovorkai. J Parasitol 2006; 92:725-9. [PMID: 16995388 DOI: 10.1645/ge-831r.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
We investigated the host selection mechanism of actinospore stages of 2 myxosporeans, Myxobolus arcticus and Thelohanellus hovorkai, infecting masu salmon (Oncorhynchus masou) and common carp (Cyprinus carpio), respectively. Discharge of the polar filaments and sporoplasm release by M. arcticus actinospores occurred within the first 5 min of exposure to skin mucus of masu salmon. The actinospores also reacted to the mucus of nonsusceptible fish, i.e., sockeye salmon (Oncorhynchus nerka) and goldfish (Carassius auratus), although the reactivity was comparatively lower. After exposure of masu, and sockeye and chum salmon (Oncorhynchus keta) to M. arcticus actinospores, the penetration of sporoplasms was observed in the fins and gills of masu and sockeye salmon to a similar extent and to a lesser extent in chum salmon. Thelohanellus hovorkai actinospores exhibited a slow response of sporoplasm release to common carp mucus as well as penetration into the gills of common carp. Neither chemoresponse to mucus of nonsusceptible fish (goldfish and sockeye salmon) nor sporoplasm invasion in goldfish was observed for T. hovorkai actinospores. These results indicate notable differences in the host selection at the time of entry between M. arcticus and T. hovorkai; the former responds quickly to fish mucus with low host specificity, whereas the latter was highly host specific in a dilatory reaction.
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Affiliation(s)
- Hiroshi Yokoyama
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan.
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Moriya S, Urawa S, Suzuki O, Urano A, Abe S. DNA microarray for rapid detection of mitochondrial DNA haplotypes of chum salmon. Mar Biotechnol (NY) 2004; 6:430-434. [PMID: 15583850 DOI: 10.1007/s10126-004-1100-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2003] [Accepted: 11/27/2003] [Indexed: 05/24/2023]
Abstract
For use in genetic stock identification, we developed an oligonucleotide (DNA) microarray hybridization method for rapid and accurate detection of nucleotide sequence variations in 20 previously identified variable nucleotide sites in about 500 bp within the 5' half of the control region of mitochondrial DNA of chum salmon (Oncorhynchus keta). The method includes immobilization of synthesized oligonucleotides containing respective polymorphic sites on a glass slide precoated with polycarbodiimide resin, a 2-hour hybridization with DNA microarray of biotinylated polymerase chain reaction fragments spanning the 5' variable portion followed by short washing, and visualization of hybridization signals by conventional ABC method and scanner-assisted computation of signal intensity on a computer. The entire process of hybridization and detection was completed within 4 hours. The resulting DNA microarray could detect all of the single nucleotide mutations and therefore could be used to identity the sequence variations defining 30 mtDNA haplotypes of chum salmon as revealed previously by nucleotide sequence analysis.
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Affiliation(s)
- Shogo Moriya
- Research and Development Center, Nisshinbo Industries, Inc., 1-2-3 Onodai, Midori-ku, Chiba 267-0056, Japan.
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Todal JA, Karlsbakk E, Isaksen TE, Plarre H, Urawa S, Mouton A, Hoel E, Koren CWR, Nylund A. Ichthyobodo necator (Kinetoplastida)--a complex of sibling species. Dis Aquat Organ 2004; 58:9-16. [PMID: 15038446 DOI: 10.3354/dao058009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Ichthyobodo necator is a parasitic flagellate that attacks fishes, causing disease problems in freshwater worldwide. Findings of similar flagellates in strictly marine fishes have indicated that ichthyobodiosis may be caused by more than 1 flagellate species. We obtained partial small subunit rDNA (ssu rDNA) sequences of 14 Ichthyobodo isolates originating from fishes in Norway, Japan, Singapore, South Africa and Brazil, and identified 8 strains or species, including 2 species infecting cultured salmon in Norway. An Ichthyobodo species isolated from the skin of Atlantic salmon parr in freshwater is suggested to represent L. necator sensu stricto, while another species, showing particular affinity for the gills, infects salmon in both fresh- and seawater. Atlantic cod is infected with a marine Ichthyobodo species unrelated to those infecting salmonids; 2 cyprinids originating from different parts of the world had related Ichthyobodo strains/species, and 2 isolates from unrelated North and South American fishes were also closely related. The phylogenetic relationships of the Ichthyobodo isolates is described, and the implications of the molecular findings on past and future morphological studies of Ichthyobodo spp. are discussed.
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Affiliation(s)
- Jan Arvid Todal
- Department of Fisheries and Marine Biology, University of Bergen, 5020 Bergen, Norway
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Székely C, Yokoyama H, Urawa S, Timm T, Ogawa K. Description of two new actinosporean types from a brook of Fuji Mountain, Honshu, and from Chitose River, Hokkaido, Japan. Dis Aquat Organ 2003; 53:127-132. [PMID: 12650245 DOI: 10.3354/dao053127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was studied. Using the cell-well plate method, a new aurantiactinomyxon type was found in 0.77% of the examined Tubifex tubifex oligochaete specimens from a brook near Yamanashi Prefectural Fisheries Experimental Station on Fuji Mountain. In 0.14% of Lumbriculus variagetus collected from Chitose River, near Chitose Salmon Hatchery, a new siedleckiella type was found, while at the same time 8.1% of the Lumbriculus spp. oligochaetes released triactinomyxons of Myxobolus arcticus. Of the examined Rhyacodrilus komarovi oligochaetes collected from the Mena River system, Hokkaido, 0.2, 0.6, 0.5 and 0.8% were infected with echinactinomyxon, neoactinomyxum and 2 types of triactinomyxon spores, respectively, and described in our previous paper. The oligochaetes released actinospores for several weeks. Actinospore infection showed high intensity in positive oligochaetes in the case of all the actinosporean types. Two of the actinospore types (aurantiactinomyxon and siedleckiella) presented here have not been previously described.
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Affiliation(s)
- Csaba Székely
- Veterinary Medical Research Institute, Hungarian Academy of Sciences, Hungaria krt. 21, 1143 Budapest, Hungary.
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Székely C, Urawa S, Yokoyama H. Occurrence of actinosporean stages of myxosporeans in an inflow brook of a salmon hatchery in the Mena River System, Hokkaido, Japan. Dis Aquat Organ 2002; 49:153-160. [PMID: 12078984 DOI: 10.3354/dao049153] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an inflow brook of a Hokkaido salmon hatchery was studied within the framework of a Japanese-Hungarian research program. Two triactinomyxon types, 1 echinactinomyxon, and 1 neoactinomyxum type were isolated from the oligochaete Rhyacodrilus komarovi Timm, 1990 collected during the survey. The aurantiactinomyxons were recorded over a period of 3 mo starting from the day after oligochaete collection. The oligochaetes released actinospores for several weeks from the first day of the study. Spore excretion of individual oligochaetes was not synchronous. Of the oligochaetes examined, 0.7, 7, 3 and 3%, were infected with the echinactinomyxon, neoactinomyxum and the 2 types of triactinomyxon spores, respectively. Actinospore infection was intense in the positive oligochaetes in all 4 types. Of the 4 actinospore types presented here, 3 are described for the first time.
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Affiliation(s)
- Csaba Székely
- Veterinary Medical Research Institute, Hungarian Academy of Sciences, Budapest.
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Lom J, Nilsen F, Urawa S. Redescription of Microsporidium takedai (Awakura, 1974) as Kabatana takedai (Awakura, 1974) comb. n. Dis Aquat Organ 2001; 44:223-230. [PMID: 11383570 DOI: 10.3354/dao044223] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Ultrastructural study of the microsporidian Microsporidium takedai from the muscles of masu salmon Oncorhynchus masou proved that this species can be assigned to the genus Kabatana Lom, Dyková and Tonguthai, 2000. The parasites develop within disintegrated sarcoplasm without any delimiting boundary or cyst. Cylindrical multinucleate meronts proliferate by serial constrictions into uninucleate stages which repeat the process. Eventually, the uninucleate stages transform into uninucleate sporonts, which divide once to produce sporoblasts, thus functioning as sporoblast mother cells. Spores, with a subterminally located anchoring disc and 3 to 4 turns of the polar tube coil, average 3.3 by 1.9 microm in size. The exospore is divided into small fields; the endospore frequently makes small invaginations into the spore inside. Phylogenetic analysis using SSU rDNA sequence consistently placed Kabatana takedai in a group consisting of Microgemma sp., Spraguea lophii and Glugea americanus. The K. takedai could easily be separated from the other species in the same group by 2 inserts in the SSU rDNA sequence.
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Affiliation(s)
- J Lom
- Institute of Parasitology, Academy of Sciences of the Czech Republic, Ceské Budéjovice.
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Shimazu T, Urawa S, Coria CO. Four species of digeneans, including Allocreadium patagonicum sp. n. (Allocreadiidae), from freshwater fishes of Patagonia, Argentina. Folia Parasitol (Praha) 2001; 47:111-7. [PMID: 10945735 DOI: 10.14411/fp.2000.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Four species of adult digeneans are reported from freshwater fishes of two lakes in Neuquén, Patagonia, Argentina. Allocreadium patagonicum sp. n. (Allocreadiidae) is described from the intestine of Percichthys colhuapiensis MacDonagh and Percichthys trucha (Cuvier et Valenciennes) (Percichthyidae) from Lago Aluminé. Three species redescribed are: Acanthostomoides apophalliformis Szidat, 1956 (Acanthostomidae) from the intestine of P. colhuapiensis and P. trucha from Lago Aluminé and of Salmo trutta (Linnaeus) (Salmonidae) from Lago Huechulafquén; Deropegus patagonicus (Szidat, 1956) comb. n. (= Genarches patagonicus Szidat, 1956) (Derogenidae) from the stomach of P. colhuapiensis, P. trucha, Oncorhynchus mykiss (Walbaum) (Salmonidae) and Salvelinus fontinalis (Mitchill) (Salmonidae) from Lago Aluminé and of S. trutta from Lago Huechulafquén; and Austrocreadium papilliferum Szidat, 1956 from the intestine of P. trucha from Lago Aluminé. The genus Polylekithum Arnold, 1934 is considered a synonym of the genus Allocreadium Looss, 1900. The genus Austrocreadium Szidat, 1956 is removed to the family Homalometridae.
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Affiliation(s)
- T Shimazu
- Nagano Prefectural College, Miwa, Japan.
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Sato S, Ando J, Ando H, Urawa S, Urano A, Abe S. Genetic Variation among Japanese Populations of Chum Salmon Inferred from the Nucleotide Sequences of the Mitochondrial DNA Control Region. Zoolog Sci 2001. [DOI: 10.2108/zsj.18.99] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Moravec F, Urawa S, Coria CO. Hysterothylacium patagonense n. sp. (Nematoda: Anisakidae) from freshwater fishes in Patagonia, Argentina, with a key to the species of Hysterothylacium in American freshwater fishes. Syst Parasitol 1997. [DOI: 10.1023/a:1005783724680] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Abstract
The numbers of the ectoparasitic flagellate Ichthyobodo necator on chum salmon fry (Oncorhynchus keta) and the host's epidermal responses to infection were monitored for 15 weeks with light and scanning electron microscopy. Parasite density on the skin peaked at 3 weeks postinfection, at an average of 625 parasites/mm2, and then decreased to near zero by week 10. The staining procedure with Alcian blue (AB, pH 2.5) and periodic acid – Schiffs reagent (PAS) revealed dramatic changes in both the degree and histochemistry of epidermal mucus secretion during the course of the parasite infections. The numbers of mucous cells declined significantly during the first 4 weeks as parasite density increased, but thereafter rose to 2000 cells/mm2 by week 8, when mucous cells stained with PAS alone predominated. This increase occurred concomitantly with a reduction in parasite density. In the control fish, the concentration of epidermal mucous cells was stable at 400 – 800 cells/mm2 during the same period and acid mucopolysaccharides (PAS-negative, AB-positive) were a major constituent of the mucous cell secretion. It is suspected that the PAS-positive mucous cells may play an important role in the defence mechanism against the parasite infection.
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Urawa S, Kusakari M. The Survivability of the Ectoparasitic Flagellate Ichthyobodo necator on Chum Salmon Fry (Oncorhynchus keta) in Seawater and Comparison to Ichthyobodo sp. on Japanese Flounder (Paralichthys olivaceus). J Parasitol 1990. [DOI: 10.2307/3282624] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Urawa S, Kusakari M. The survivability of the ectoparasitic flagellate Ichthyobodo necator on chum salmon fry (Oncorhynchus keta) in seawater and comparison to Ichthyobodo sp. on Japanese flounder (Paralichthys olivaceus). J Parasitol 1990; 76:33-40. [PMID: 2299525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Experimental studies revealed that a freshwater ectoparasitic flagellate Ichthyobodo necator (Henneguy, 1883) could survive and reproduce in seawater after infected chum salmon fry, Oncorhynchus keta (Walbaum), were transferred directly from fresh water to 33% seawater. Minor morphological changes (slight reduction in body width, loss of twistlike wrinkles on body surface, and reduction in contractile vacuoles) were observed in the attached form of I. necator following transfer to seawater. The field survey also confirmed that I. necator occurs on chum salmon fry in seawater estuaries (salinity 17-34%) and in freshwater habitats. It was assumed that I. necator acquired salinity tolerance as a result of adapting to the migratory behavior of its anadromous host. Two morphologically similar bodonids, I. necator from chum salmon and Ichthyobodo sp. from marine Japanese flounder, Paralichthys olivaceus (Temminck and Schlegel), were differentiated by cross-infection experiments. Thus, the parasite from marine flounder should be regarded as a separate species from I. necator.
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Affiliation(s)
- S Urawa
- Hokkaido Salmon Hatchery, Fisheries Agency of Japan, Sapporo
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