Green fluorescence from cnidarian hosts attracts symbiotic algae

Yusuke Aihara, Shinichiro Maruyama, Andrew H. Baird, Akira Iguchi, Shunichi Takahashi, Jun Minagawa

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


Reef-building corals thrive in nutrient-poor marine environments because of an obligate symbiosis with photosynthetic dinoflagellates of the genus Symbiodinium. Symbiosis is established in most corals through the uptake of Symbiodinium from the environment. Corals are sessile for most of their life history, whereas free-living Symbiodinium are motile; hence, a mechanism to attract Symbiodinium would greatly increase the probability of encounter between host and symbiont. Here, we examined whether corals can attract free-living motile Symbiodinium by their green fluorescence, emitted by the excitation of endogenous GFP by purple-blue light. We found that Symbiodinium have positive and negative phototaxis toward weak green and strong purple-blue light, respectively. Under light conditions that cause corals to emit green fluorescence, (e.g., strong blue light), Symbiodinium were attracted toward live coral fragments. Symbiodinium were also attracted toward an artificial green fluorescence dye with similar excitation and emission spectra to coral-GFP. In the field, more Symbiodinium were found in traps painted with a green fluorescence dye than in controls. Our results revealed a biological signaling mechanism between the coral host and its potential symbionts.

Original languageEnglish
Pages (from-to)2118-2123
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number6
Publication statusPublished - 2019 Feb 5
Externally publishedYes


  • Coral
  • Fluorescence
  • GFP
  • Phototaxis
  • Symbiosis

ASJC Scopus subject areas

  • General


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