Coral symbiotic algae calcify ex hospite in partnership with bacteria.
Dinoflagellates of the genus Symbiodinium are commonly recognized as invertebrate endosymbionts that are of central importance for the functioning of coral reef ecosystems. However, the endosymbiotic phase within Symbiodinium life history is inherently tied to a more cryptic free-living (ex hospite) phase that remains largely unexplored. Here we show that free-living Symbiodinium spp. in culture commonly form calcifying bacterial-algal communities that produce aragonitic spherulites and encase the dinoflagellates as endolithic cells. This process is driven by Symbiodinium photosynthesis but occurs only in partnership with bacteria. Our findings not only place dinoflagellates on the map of microbial-algal organomineralization processes but also point toward an endolithic phase in the Symbiodinium life history, a phenomenon that may provide new perspectives on the biology and ecology of Symbiodinium spp. and the evolutionary history of the coral-dinoflagellate symbiosis.
Department of Biology, Center for Environmental and Marine Studies (CESAM), jfrommlet@ua.pt.
Jörg C
http://orcid.org/0000-0001-7399-3021
JC
Frommlet
Department of Biology, Center for Environmental and Marine Studies (CESAM).
Maria L
ML
Sousa
Department of Biology, Center for Environmental and Marine Studies (CESAM).
Artur
A
Alves
Autonomous Section of Health Sciences, Center for Cell Biology, and Institute for Biomedicine, Santiago Campus, University of Aveiro, 3810-193 Aveiro, Portugal; and.
Sandra I
SI
Vieira
Functional Plant Biology & Climate Change Cluster, University of Technology Sydney, Broadway, NSW 2007, Australia.
David J
DJ
Suggett
Department of Biology, Center for Environmental and Marine Studies (CESAM).
João
J
Serôdio
D000143:Acids / Q000737:chemistry; D000423:Alcian Blue / Q000737:chemistry; D000818:Animals; D037421:Anthozoa / Q000382:microbiology*; D000900:Anti-Bacterial Agents / Q000737:chemistry; D001419:Bacteria; D018441:Biofilms; D002118:Calcium / Q000737:chemistry*; D002138:Calibration; D004141:Dinoflagellida / Q000502:physiology*; D017753:Ecosystem; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000502:physiology; D013559:Symbiosis; D014867:Water / Q000737:chemistry
D000143:Acids; D000900:Anti-Bacterial Agents; D045332:Photosystem II Protein Complex; D014867:Water; D000423:Alcian Blue; D002118:Calcium
Symbiodinium; coral symbiont; endolithic algae; life history; microbial–algal calcification