title: Coral-the world's most diverse symbiotic ecosystem.
abstract: Zooxanthellate corals (i.e. those harbouring Symbiodinium) are the main builders of the world's shallow-water marine coral reefs. They represent intimate diverse symbioses between coral animals, single-celled photosynthetic dinoflagellates (Symbiodinium spp.), other microscopic eukaryotes, prokaryotes and viruses. Crabs and other crustaceans, worms, sponges, bivalves and hydrozoans, fishes, sea urchins, octopuses and sea stars are itinerant members of these 'rainforests of the sea'. This review focuses on the biodiversity of scleractinian coral animals and their best studied microscopic epi- and endosymbionts. In relation to coral-associated species diversity, Symbiodinium internal transcribed spacer region sequence types tally 10(2) -10(3) or up to ~15 different operational taxonomic units (OTUs, or putative species at the 97% sequence identity level; this cut-off was chosen based on intragenomic sequence diversity observed in monoclonal cultures) and prokaryotes (mostly bacterial) total 10(2) -10(4) OTUs. We analysed all publically accessible 16S rRNA gene sequence data and found Gammaproteobacteria were extremely abundant, followed by Alphaproteobacteria. Notably, Archaea were poorly represented and 'unassigned OTUs' were abundant in data generated by high-throughput DNA sequencing studies of corals. We outline and compare model systems that could be used in future studies of the coral holobiont. In our future directions, we recommend a global coral sampling effort including substantial attention being paid to method of coral tissue acquisition, which compartments (mucus, tissue, skeleton) to explore, broadening the holobiont members considered and linking biodiversity with functional investigations.
authors.affiliation: Department of Chemistry and Biotechnology, Faculty of Science, Engineering & Technology, Swinburne University of Technology, Melbourne, Vic., 3122, Australia.
authors.forename: Linda L
authors.initials: LL
authors.lastname: Blackall
authors.affiliation: Marine Microbiology Research Group, Department of Biology, University of Bergen, Thormøhlensgate 53B, 5020, Bergen, Norway.
authors.forename: Bryan
authors.initials: B
authors.lastname: Wilson
authors.affiliation: Australian Institute of Marine Science, PMB No. 3, Townsville MC, Qld., 4810, Australia.|School of BioSciences, The University of Melbourne, Parkville, Vic., 3010, Australia.
authors.forename: Madeleine J H
authors.initials: MJ
authors.lastname: van Oppen
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000235:genetics / Q000382:microbiology*; D001105:Archaea / Q000145:classification; D001419:Bacteria / Q000145:classification*; D044822:Biodiversity; D057894:Coral Reefs; D004269:DNA, Bacterial / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D004141:Dinoflagellida / Q000145:classification*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S
keywords: Symbiodinium; bioinformatics; coral; coral model; holobiont; microbiome