Ultrastructural studies on the establishment, maintenance and breakdown of a coral-zooxanthella symbiotic system

• Project/Area Number: 24570071
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Morphology/Structure
• Research Institution: Kochi University
• Principal Investigator: OKUDA Kazuo 高知大学, 教育研究部総合科学系, 教授 (40152417)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Project Status: Completed (Fiscal Year 2014)
• Budget Amount: ¥5,590,000 (Direct Cost: ¥4,300,000、Indirect Cost: ¥1,290,000); Fiscal Year 2014: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2013: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000); Fiscal Year 2012: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
• Keywords: サンゴ / 褐虫藻 / 細胞共生 / 微細構造 / 微細形態

Outline of Final Research Achievements

Fine structure during the establishment, maintenance and breakdown of a coral-zooxanthella symbiotic system was examined. Suitable chemical and freeze fixation methods were applied for observing various cellular membranes clearly. When corals were treated with high temperatures, gastroderm cells without zooxanthellae autolyzed first, followed by the disconnection of cells with zooxanthellae away from gastroderm, so that the symbiotic system was broken down. Zooxanthellae in coral cells were found to have several distinct layers on the cortex. After cell divisions of zooxanthellae, symbiosome membranes and these layers were cleaved by constriction into two parts and enveloped the daughter cells. This process may ensure to distribute zooxanthellae into coral cells for the maintenance of the symbiotic system. Free-living zooxanthellae were attracted inward the gastric cavities of polyps in early developing corals and incorporated into gastroderm cells to establish the symbiotic systems.

Research Products

• [Journal Article] Detection of characteristic heterochromatin distribution, highly amplified rRNA genes and presence of the human satellite III DNA motif in the scleractinian coral Echinophyllia aspera Ellis and Solander 1788 (2014)
  • Author(s): Taguchi T, Kubota S, Mezaki T, Sekida S, Okuda K, Nakachi S, Shinbo T, Iiguni Y and Tominaga A
  • Journal Title: Chromosome Science Volume: 16 Pages: 33-38
  • NAID: 130004707283
  • Peer Reviewed
• [Journal Article] Molecular cytogenetic analysis of the scleractinian coral Acropora solitaryensis Veron & Wallace 1984 (2014)
  • Author(s): Taguchi T, Mezaki T, Iwase F, Sekida S, Kubota S, Fukami H, Okuda K, Shinbo T, Oshima S, Iiguni Y, Testa JR and Tominaga A
  • Journal Title: Zoological Science Volume: 31 Pages: 89-94
  • NAID: 40019989087
  • Peer Reviewed
• [Journal Article] サンゴに共生する褐虫藻の微細構造と生理学的挙動 (2012)
  • Author(s): 関田諭子・奥田一雄
  • Journal Title: 海洋と生物 Volume: 34 Pages: 338-342
• [Presentation] サンゴ細胞内における褐虫藻の細胞分裂の電子顕微鏡観察 (2014)
  • Author(s): 関田諭子、奥田一雄
  • Organizer: 日本サンゴ礁学会
  • Place of Presentation: 高知市高知城ホール
  • Year and Date: 2014-11-26 – 2014-12-01
• [Presentation] Ribosomal RNA gene mapping and manifestation of sex chromosomes on the scleractinian coral Acropora Solitaryensis Veron & Wallace (2014)
  • Author(s): Taguchi T, Kubota S, Mezaki T, Sekida S, Okuda K, Tominaga A
  • Organizer: 10th Asia-Pacific Marine Biotechnology Conference
  • Place of Presentation: Taipei, Taiwan
• [Presentation] Ultrastructure of cortical and extracellular structures of zooxanthellae during cell division in a coral cell (2013)
  • Author(s): Sekida S, Okuda K
  • Organizer: 10th international phycological congress
  • Place of Presentation: Orlando, Florida, USA