title: Trehalose is a chemical attractant in the establishment of coral symbiosis.
abstract: Coral reefs have evolved with a crucial symbiosis between photosynthetic dinoflagellates (genus Symbiodinium) and their cnidarian hosts (Scleractinians). Most coral larvae take up Symbiodinium from their environment; however, the earliest steps in this process have been elusive. Here we demonstrate that the disaccharide trehalose may be an important signal from the symbiont to potential larval hosts. Symbiodinium freshly isolated from Fungia scutaria corals constantly released trehalose (but not sucrose, maltose or glucose) into seawater, and released glycerol only in the presence of coral tissue. Spawning Fungia adults increased symbiont number in their immediate area by excreting pellets of Symbiodinium, and when these naturally discharged Symbiodinium were cultured, they also released trehalose. In Y-maze experiments, coral larvae demonstrated chemoattractant and feeding behaviors only towards a chamber with trehalose or glycerol. Concomitantly, coral larvae and adult tissue, but not symbionts, had significant trehalase enzymatic activities, suggesting the capacity to utilize trehalose. Trehalase activity was developmentally regulated in F. scutaria larvae, rising as the time for symbiont uptake occurs. Consistent with the enzymatic assays, gene finding demonstrated the presence of a trehalase enzyme in the genome of a related coral, Acropora digitifera, and a likely trehalase in the transcriptome of F. scutaria. Taken together, these data suggest that adult F. scutaria seed the reef with Symbiodinium during spawning and the exuded Symbiodinium release trehalose into the environment, which acts as a chemoattractant for F. scutaria larvae and as an initiator of feeding behavior- the first stages toward establishing the coral-Symbiodinium relationship. Because trehalose is a fixed carbon compound, this cue would accurately demonstrate to the cnidarian larvae the photosynthetic ability of the potential symbiont in the ambient environment. To our knowledge, this is the first report of a chemical cue attracting the motile coral larvae to the symbiont.
authors: Department of Reproductive Sciences, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, United States of America.
authors: Mary
authors: M
authors: Hagedorn
authors: Department of Reproductive Sciences, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, United States of America.
authors: Virginia
authors: V
authors: Carter
authors: Department of Reproductive Sciences, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, United States of America.
authors: Nikolas
authors: N
authors: Zuchowicz
authors: Department of Reproductive Sciences, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, United States of America.
authors: Micaiah
authors: M
authors: Phillips
authors: Department of Reproductive Sciences, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, United States of America.
authors: Chelsea
authors: C
authors: Penfield
authors: Department of Reproductive Sciences, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, United States of America.
authors: Brittany
authors: B
authors: Shamenek
authors: Department of Biology, Swarthmore College, Swarthmore, Pennsylvania, United States of America.
authors: Elizabeth A
authors: EA
authors: Vallen
authors: Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, United States of America.
authors: Frederick W
authors: FW
authors: Kleinhans
authors: Biology Department, Whitman College, Walla Walla, Washington, United States of America.
authors: Kelly
authors: K
authors: Peterson
authors: Biology Department, Whitman College, Walla Walla, Washington, United States of America.
authors: Meghan
authors: M
authors: White
authors: Biology Department, Whitman College, Walla Walla, Washington, United States of America.
authors: Paul H
authors: PH
authors: Yancey
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000378:metabolism*; D002630:Chemotactic Factors / Q000378:metabolism*; D057894:Coral Reefs; D004141:Dinoflagellida / Q000378:metabolism*; D013559:Symbiosis / Q000502:physiology*; D014199:Trehalose / Q000378:metabolism*
chemical_list: D002630:Chemotactic Factors; D014199:Trehalose
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