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Published Papers 【 display / non-display 】

• Environmental pH signals the release of monosaccharides from cell wall in coral symbiotic alga

  Yuu Ishii, Hironori Ishii, Takeshi Kuroha, Ryusuke Yokoyama, Ryusaku Deguchi, Kazuhiko Nishitani, Jun Minagawa,Masakado Kawata, Shunichi Takahashi, Shinichiro Maruyama

  eLife   12   e80628   2023.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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    DOI

• Moonrise timing is key for synchronized spawning in coral Dipsastraea speciosa

  Che-Hung Lin, Shunichi Takahashi, Aziz J. Mulla, Yoko Nozawa

  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA ( NATL ACAD SCIENCES )  118 ( 34 )   2021.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Synchronized mass coral spawning typically occurs several days after a full moon once a year. It is expected that spawning day is determined by corals sensing environmental change regulated by the lunar cycle (i.e., tide or moonlight); however, the exact regulatory mechanism remains unknown. Here, we demonstrate how moonlight influences the spawning process of coral, Dipsastraea speciosa. When corals in the field were shaded 1 and 3 d before the full moon or 1 d after the full moon, spawning always occurred 5 d after shading commenced. These results suggest moonlight suppresses spawning: a hypothesis supported by laboratory experiments in which we monitored the effects of experimental moonlight (night-light) on spawning day. Different night-light treatments in the laboratory showed that the presence of a dark period between day-light and night-light conditions eliminates the suppressive effect of night-light on spawning. In nature, moonrise gets progressively later during the course of the lunar cycle, shifting to after sunset following the day of the full moon. Our results indicate that this period of darkness between sunset and moonrise triggers synchronized mass spawning of D. speciosa in nature.

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• Photo-movement of coral larvae influences vertical positioning in the ocean

  Aziz J. Mulla, Che-Hung Lin, Shunichi Takahashi, Yoko Nozawa

  CORAL REEFS ( SPRINGER )  40 ( 4 ) 1297 - 1306   2021.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Behaviour can have profound consequences for the dispersal potential of an organism. In the marine environment, larvae rely heavily on oceanic currents to migrate from one area to another. As oceanic currents are faster in the shallows, the vertical positioning of larvae during dispersal is a key factor regulating the distance individuals can travel. Up until now, the vertical positioning of coral larvae has been largely explained by buoyancy, as well as changes in physical and chemical cues. However, here we show that in larvae of coral Pocillopora verrucosa, vertical positioning is influenced by photo-movement. We examined the reaction to light of five coral species in the laboratory and found that only larvae of P. verrucosa, but not other species, displayed a positive photo-response (i.e. an accumulation of larvae close to the light source). This reaction was observed irrespective to the orientation of light from the top, bottom or side. In the field, P. verrucosa larvae accumulated in the top halves of transparent chambers at all depths (1, 7, 15 m), whereas such behaviour failed to occur in dark chambers. Our results demonstrate that light can play an important role for coral larvae to regulate vertical positioning during dispersal and provides a hypothesis that positive photo-movement might allow larvae to disperse further and contribute to the wide geographical distribution of P. verrucosa in the Indo-Pacific.

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• Chloroplast acquisition without the gene transfer in kleptoplastic sea slugs, Plakobranchus ocellatus

  Maeda T, Takahashi S, Yoshida T, Shimamura S, Takaki Y, Nagai Y, Toyoda A, Suzuki Y, Arimoto A, Ishii H, Satoh N, Nishiyama T, Hasebe M, Maruyama T, Minagawa J, Obokata J, Shigenobu S

  eLife ( ELIFE SCIENCES PUBLICATIONS LTD )  10   10:e60176   2021.04 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Some sea slugs sequester chloroplasts from algal food in their intestinal cells and photosynthesize for months. This phenomenon, kleptoplasty, poses a question of how the chloroplast retains its activity without the algal nucleus. There have been debates on the horizontal transfer of algal genes to the animal nucleus. To settle the arguments, this study reported the genome of a kleptoplastic sea slug, Plakobranchus ocellatus, and found no evidence of photosynthetic genes encoded on the nucleus. Nevertheless, it was confirmed that light illumination prolongs the life of mollusk under starvation. These data presented a paradigm that a complex adaptive trait, as typified by photosynthesis, can be transferred between eukaryotic kingdoms by a unique organelle transmission without nuclear gene transfer. Our phylogenomic analysis showed that genes for proteolysis and immunity undergo gene expansion and are up-regulated in chloroplast-enriched tissue, suggesting that these molluskan genes are involved in the phenotype acquisition without horizontal gene transfer.

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• Loss of symbiont infectivity following thermal stress can be a factor limiting recovery from bleaching in cnidarians

  Kishimoto Mariko, Baird Andrew H., Maruyama Shinichiro, Minagawa Jun, Takahashi Shunichi

  ISME JOURNAL ( SPRINGERNATURE )  14 ( 12 ) 3149 - 3152   2020.12 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Increases in seawater temperature can cause coral bleaching through loss of symbiotic algae (dinoflagellates of the family Symbiodiniaceae). Corals can recover from bleaching by recruiting algae into host cells from the residual symbiont population or from the external environment. However, the high coral mortality that often follows mass-bleaching events suggests that recovery is often limited in the wild. Here, we examine the effect of pre-exposure to heat stress on the capacity of symbiotic algae to infect cnidarian hosts using the Aiptasia (sea-anemone)-Symbiodiniaceae model system. We found that the symbiont strainBreviolumsp. CS-164 (ITS2 type B1), both free-living and in symbiosis, loses the capacity to infect the host following exposure to heat stress. This loss of infectivity is reversible, however, a longer exposure to heat stress increases the time taken for reversal. Under the same experimental conditions, the loss of infectivity was not observed in another strainBreviolum psygmophilumCCMP2459 (ITS2 type B2). Our results suggest that recovery from bleaching can be limited by the loss of symbiont infectivity following exposure to heat stress.

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Other Papers 【 display / non-display 】

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• Symbiotic relationship between corals and algae : from association to disassociation

    68 ( 1 ) 24 - 29   2016  [Refereed]

   

• Photoinhibition and Photoprotection Mechanisms under Excessive Light Conditions

    23 ( 2 ) 57 - 63   2013  [Refereed]

   

Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Adaptation of corals to future warm environments

  高橋 俊一

  Seminar (Academia Sinica)  2018  -  2018 

• Mechanisms for initiating coral-Symbiodinium symbiosis

  高橋 俊一

  An Australian Academy of Science Boden Research Conference  2018  -  2018 

• Size-dependent symbiont specificity in cnidarian-dinoflagellate symbiosis

  高橋 俊一

  The 13th International Colloquium on Endocytobiology and Symbiosis  2016  -  2016 

• Saving coral reefs: an arranged marriage in alga-coral symbiosis

  高橋 俊一

  第33回つくば藻類・プロティストフォーラム  2014  -  2014 

• Photoinhibition and photoprotection under excessive light conditions

  高橋 俊一

  Symposium “New paradigm in photoinhibition research”, the 54th Annual Meeting of the Japanese Society of Plant Physiologists  2013  -  2013 

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

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

• Challenging research (development)

  Project Year: 2024.06  -  2029.03 

  Direct: 19,900,000 (YEN)  Overheads: 5,970,000 (YEN)  Total: 25,870,000 (YEN)

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2024.04  -  2028.03 

  Direct: 16,770,000 (YEN)  Overheads: 12,900,000 (YEN)  Total: 3,870,000 (YEN)

• Grant-in-Aid for Scientific Research(A)

  Project Year: 2024.04  -  2028.03 

  Direct: 36,800,000 (YEN)  Overheads: 11,040,000 (YEN)  Total: 47,840,000 (YEN)

• Grant-in-Aid for Scientific Research(A)

  Project Year: 2023.04  -  2027.03 

  Direct: 36,200,000 (YEN)  Overheads: 10,860,000 (YEN)  Total: 47,060,000 (YEN)

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2023.04  -  2027.03 

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Other External funds 【 display / non-display 】

• Project Year: 2012  -  2014 

  Member: TAKAHASHI Shunichi  Offer Organization: Australian Research Council

  Total: 30,000,000 (YEN)

• Project Year: 2011.01  -  2015.12 

  Member: TAKAHASHI Shunichi  Offer Organization: Australian Research Council

  Total: 60,000,000 (YEN)

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• 2024.03

  　

  　

  

• 2024.01

  　

  　

  

• 2023.10

  　

  　

  

• 2023.09

  　

  　

  

• 2023.07

  　

  　

  

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