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• Comparative morphology of integumentary structures in tunicate

• Algal symbiosis in marine invertebrates

• Tunic morphology and functions

• Ascidian-cyanobacteria symbiosis system

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Published Papers 【 display / non-display 】

• The chromosomal genome sequence of the photosymbiotic ascidian, Trididemnum clinides Kott, 1977 and its associated microbial metagenome sequences [version 2; peer review: 2 approved]

  Hirose E., Lopez JV, Oatley G e

  Wellcome Open Research   10   357   2025.10 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

• Optical properties of the jellyfish surface above the waterline: microvillar array in pleustonic hydrozoans

  Euichi Hirose, Nicolò Brunelli, Daisuke Sakai, Hiroshi Kakiuchida, Jun Nishikawa

  Zoological Letters ( Springer Science and Business Media LLC )  11 ( 1 )   2025.09 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Abstract Background The transparent jellyfish body is often difficult to see underwater, as its refractive index is similar to that of seawater, resulting in a low light reflectance on the body surface. Nevertheless, the outlines of jellyfish can be recognized by the slight reflection of light from their body surfaces. In some jellyfish species, the epidermis covering the body surface has an array of microvilli, nanostructures that can potentially reduce light reflection. However, the anti-reflective effect is minimal in water, as the difference in the refractive indices of tissue and seawater is so small that reflectance is low, even on flat surfaces. In jellyfish that have pneumatophores, structures used in floating and drifting on the sea surface, light reflection on the surface is expected to be large and noticeable owing to the large differences in refractive indices between the pneumatophore exposed above the water surface and air. In the current study, we examined the epidermal ultrastructure and refractive index of the pneumatophores of a Portuguese man o' war (Physalia physalis) and a by-the-wind sailor (Velella velella). Results The refractive index of P. physalis pneumatophores measured with an Abbe refractometer was approximately 1.344. Microvillar arrays were found in epidermal cells of both P. physalis and V. velella. Based on the length, thickness, and pitch of the microvilli, we constructed simplified structural models for the simulation of light reflection using rigorous coupled wave analysis (RCWA). Our simulations showed that reflectance on the microvillar models could be greater or less than that on the flat surface, depending on light conditions (wavelength and angle of incidence), but with an overall effect of reduced reflection. Reflection reduction in microvillar models was particularly significant at large incident angles, where reflectance was extremely high on the flat surface. Conclusions Microvillar arrays found on the epidermis potentially reduce surface reflections of the pneumatophore and contribute to the reduction in visibility of the pleustonic hydrozoans above the sea surface. Moreover, less reflection at the pneumatophore surface indicates greater transmission of light through transparent bodies, potentially providing a counter-illumination effect that obscures the shadow of the hydrozoan bodies, depending on the intensity of ambient light.

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• Ascidian Larvae Prefer Hydrophobic Substrates for Settlement

  Noburu Sensui, Euichi Hirose

  Zoological Science ( Zoological Society of Japan )  42 ( 5 ) 478 - 483   2025.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  The selection of settlement sites by larvae is a crucial event in the life cycle of sessile animals, as they are usually unable to migrate after settlement and metamorphosis into sessile forms. For example, some species prefer hydrophilic substrates, whereas others prefer hydrophobic sub- strates. Understanding larval preferences for substrates will provide an essential basis for control- ling biofouling. In this study, we focused on the water wettability of substrates for settlement and investigated larval substrate preference in three ascidian species, Phallusia philipinennsis, Ascidia sydneiensis, and Ciona robusta (= C. intestinalis type A), using a four-choice assay with substrates of different water wettability (contact angle of a water droplet): silicone rubber (115°), polyvinyl chloride (80°), glass (31°), and hydrophilic film SH2CLHF (14°). In some regions of the world, A. sydneiensis and C. robusta are often noted as invasive species and are serious biofoulants. In all three species, larvae showed a significant preference for more hydrophobic substrates, and none settled on the most hydrophilic substrate, that is, SH2CLHF. It is difficult to explain why ascid- ian larvae prefer a more hydrophobic substrate, since hydrophobic materials, such as silicon, are often used as antifouling measures. This inconsistent substrate preference can be applied to miti- gate biofouling.

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• Butterfly pupal wing tissue with an eyespot organizer

  Joji M. Otaki, Atsuko Tanaka, Euichi Hirose

  Cells & Development ( Elsevier BV )    203992 - 203992   2025.01 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Ascidian larvae discriminate nano-scale difference in surface structures during substrate selection for settlement

  Daisuke Sakai, Noburu Sensui, Euichi Hirose

  Zoological Science ( Zoological Society of Japan )  41 ( 6 ) 564 - 569   2024.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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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

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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)

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

  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)

• 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)

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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