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• Comparative morphology of integumentary structures in tunicate

• Algal symbiosis in marine invertebrates

• Tunic morphology and functions

• Ascidian-cyanobacteria symbiosis system

Published Papers 【 display / non-display 】

Published Papers 【 display / non-display 】

• Regeneration of tunic cuticle is suppressed in edible ascidian Halocynthia roretzi contracting soft tunic syndrome

  K Nakayama, Y Obayashi, L Munechika, SI Kitamura, T Yanagida, M Honjo, S Murakami, E Hirose

  Diseases of Aquatic Organisms ( Inter-Research Science Center )  159   37 - 48   2024.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Soft tunic syndrome is an infectious disease caused by the flagellate Azumiobodo hoyamushi, which severely damages the aquaculture of the edible ascidian Halocynthia roretzi. Tunic is a cellulosic extracellular matrix entirely covering the body in ascidians and other tunicates, and its dense cuticle layer covers the tunic surface as a physical barrier against microorganisms. When the tunic of intact H. roretzi individuals was cut into strips, electron-dense fibers (DFs) appeared on the cut surface of the tunic matrix and aggregated to regenerate a new cuticular layer in seawater within a few days. DF formation was partially or completely inhibited in individuals with soft tunic syndrome, and DF formation was also inhibited by the presence of some proteases, indicating the involvement of proteolysis in the process of tunic softening as well as cuticle regeneration. Using pure cultures of the causative flagellate A. hoyamushi, the expression of protease genes and secretion of some proteases were confirmed by RNA-seq analysis and a 4-methylcoumaryl-7-amide substrate assay. Some of these proteases may degrade proteins in the tunic matrix. These findings suggest that the proteases of A. hoyamushi is the key to understanding the mechanisms of cuticular regeneration inhibition and tunic softening.

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• Optical properties of body mucus secreted from the coral reef sea slugs: Measurement of refractive indices and relative absorption spectra

  Ryogo Takano, Euchi Hirose

  Zoological Studies   23 ( 2 ) 1 - 10   2024.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Fine structures along the alimentary canal in a holoplanktonic gastropod, <i>Pterotrachea coronata</i>

  Jun Nishikawa, Euichi Hirose

  Plankton and Benthos Research ( The Plankton Society of Japan/The Japanese Association of Benthology )  18 ( 4 ) 198 - 205   2023.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat

  Daisuke Sakai, Jun Nishikawa, Hiroshi Kakiuchida, Euichi Hirose

  PeerJ ( PeerJ )  10 ( e14284 ) e14284 - e14284   2022.10 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Background Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, Pterotrachea coronata, the visceral nucleus is an opaque organ located at the posterior end of its alimentary system, but this organ has a mirrored surface to conceal its internal opaque tissue. Results Our ultrastructural observation proved that the cortex of the visceral nucleus comprised a stack of thin cellular lamellae forming a Bragg reflector, and the thickness of lamellae (0.16 µm in average) and the spaces between the lamellae (0.1 µm in average) tended to become thinner toward inner lamellae. Based on the measured values, we built virtual models of the multilamellar layer comprising 50 lamellae and spaces, and the light reflection on the models was calculated using rigorous coupled wave analysis to evaluate their properties as reflectors. Our simulation supported the idea that the layer is a reflective tissue, and the thickness of the lamella/space must be chirped to reflect sunlight as white/silver light, mostly independent of the angle of incidence. Conclusions In P. coronata, the cortex of the visceral nucleus comprised multicellular lamellae that form a chirped Bragg reflector. It is distinct in structure from the intracellular Bragg structures of common iridophores. This novel Bragg reflector demonstrates the diversity and convergent evolution of reflective tissue using reflectin-like proteins in Mollusca.

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• Innate immunity in the edible ascidian Halocynthia roretzi developing soft tunic syndrome: Hemolymph can eliminate the causative flagellates and discriminate allogeneic hemocytes

  Tetsuya Yanagida, Kei Nakayama, Tomoo Sawada, Miho Honjo, Shoko Murakami, Takaji Iida, Euichi Hirose, Shin-Ichi Kitamura

  Fish & Shellfish Immunology ( Elsevier BV )  127   659 - 665   2022.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  The infection of the kinetoplastid flagellate Azumiobodo hoyamushi causes soft tunic syndrome that often results in mass mortality in the aquaculture of the edible ascidian Halocynthia roretzi. In the diseased ascidian individuals, the flagellates are exclusively found in the tunic matrix that entirely cover the epidermis, and never invade into internal tissues, such as a mantle. The present study for the first time demonstrated that the ascidian blood plasma and hemolymph have an activity to agglutinate and disintegrate the flagellates, suggesting the innate immunity protects the internal tissue from the invasion of A. hoyamushi. This activity is indifferent between the healthy and the diseased individuals. Allo-specific recognition and cytotoxic reaction among ascidian hemocytes, so-called contact reaction, occur among the individuals of healthy–healthy, healthy–diseased, and diseased–diseased combination, and therefore, the hemocytes from diseased individuals still retain the allo-reactivity. Moreover, the allo-reactive combinations are not changed under the presence of the flagellates, indicating the flagellates neither suppress nor induce the effector system of the contact reaction. These results suggest that the infection of A. hoyamushi does not impair the innate immunity in the ascidian hemolymph.

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Other Papers 【 display / non-display 】

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• Innate immunity in the edible ascidian Halocynthia roretzi developing soft tunic syndrome

  柳田哲矢, 仲山慶, 澤田知夫, 本庄美穂, 村上祥子, 飯田貴次, 広瀬裕一, 北村真一

  日本寄生虫学会大会プログラム・抄録集   92nd   2023

   

  J-GLOBAL

• What are the benefits in the ascidian-Prochloron symbiosis?

  その他の著者

  Endocytobiosis and Cell Research ( その他の出版社 )  15   51 - 62   2004

   

• Colonial allorecognition, hemolytic rejection, and viviparity in botryllid ascidians.

  E. Hirose

  Zoological Science ( 日本動物学会 )    2003.03

   

• Recent advances in molecular biology on pigmentation of the medaka, Oryzias latipes.

  J. Matsumoto, H. Ono, and E. Hirose

  The Fish Biology Journal MEDAKA ( The Fish Biology Journal MEDAKA )    1996.11

   

• Allorecognition in compound ascidians.

  Y. Saito, E. Hirose, H. Watanabe

  International Journal of Developmental Biology ( International Journal of Developmental Biology )    1994.05

   

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Academic Awards 【 display / non-display 】

Academic Awards 【 display / non-display 】

• Zoological Science Award

  2016.11.17   Zoological Society of Japan   Fine structure of the integumentary cuticles and alimentary tissue of pycnophyid kinorhynchs Pycnophyes oshoroensis and Kinorhynchus yushini (Kinorhyncha, Homalorhagida)

  Winner: Euichi Hirose, Hiroshi Yamasaki

Grant-in-Aid for Scientific Research 【 display / non-display 】

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• Comprehensive analysis of optical properties and evolutionary and diversification processes in the body surface of gelatinous zooplankton

  Grant-in-Aid for Scientific Research(B)

  Project Year: 2023.04  -  2028.03 

  Direct: 11,300,000 (YEN)  Overheads: 14,690,000 (YEN)  Total: 3,390,000 (YEN)

• The pathogenic flagellate Azumiobodo hoyamushi versus host ascidian immune system

  Grant-in-Aid for Scientific Research(B)

  Project Year: 2023.04  -  2026.03 

  Direct: 14,000,000 (YEN)  Overheads: 18,200,000 (YEN)  Total: 4,200,000 (YEN)

• Does nano-structures on the body surface decrease adhesive/friction forces?

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2021.04  -  2024.03 

  Direct: 3,200,000 (YEN)  Overheads: 4,160,000 (YEN)  Total: 960,000 (YEN)

• Does nano-structures on the body surface decrease adhesive/friction forces?

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2021.04  -  2024.03 

  Direct: 3,200,000 (YEN)  Overheads: 4,160,000 (YEN)  Total: 960,000 (YEN)

• Adaptive strategy of soft bodies in gelatinous zooplankton: ultrastructural and optical approaches

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2020.04  -  2023.03 

  Direct: 3,300,000 (YEN)  Overheads: 4,290,000 (YEN)  Total: 990,000 (YEN)

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• Project Year: 2010  -  2010 

  Direct: 0 (YEN)  Overheads: 0 (YEN)  Total: 0 (YEN)

• Project Year: 2007  -  2007 

  Direct: 0 (YEN)  Overheads: 0 (YEN)  Total: 0 (YEN)

• Project Year: 1992  -  1992 

  Direct: 0 (YEN)  Overheads: 0 (YEN)  Total: 0 (YEN)

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• 2023.09