A plethora of human diseases and much of human physiology have been elucidated by studies using animal models. So too knowledge of scleractinian corals, in particular the role of Symbiodinium, has been advanced by studies with the coral model Exaiptasia. Other models could include the close scleractinian relative the Corallimorpharia and scleractinian coral cell cultures. All models are symbioses between an animal and a dinoflagellate (Symbiodinium), but there are numerous distinguishing attributes which allow the researcher to select one model over the others. For example, Exaiptasia can occur in the aposymbiotic state which is appealing when attempting to reveal the role of Symbiodinium in coral phenotypes.
Exaiptasia and Corallimorpharia have several traits in common like relative ease of lab culture, ability to obtain a large number of clonal polyps, demonstration of both sexual and asexual reproduction and formation of stable symbioses with a range of Symbiodinium species. However, there is much more information on the biology and ecology and prolific genomic and proteomic data on Exaiptasia compared to Corallimorpharia.
Apart from assessments of coral bacterial pathogens, coral models have seldom been used in coral fungal, prokaryote or viral studies. To address this paucity, we have grown Great Barrier Reef sourced sea anemomes for >12 months in the laboratory. We identified the animal as Exaiptasia pallida (by 18S rRNA gene analysis) and coming from 4 different genotypes (by SNP analysis). The commonest Symbiodinium (from ITS2 analyses) was clade B1 (99%) and the prokaryotic microbiome (from Illumina NGS of 16S rRNA genes) comprised the phyla Proteobacteria (57%), Bacteriodetes (16%), Planctomycetes (7.5%) and Cyanobacteria (5%). The abundant coral-associated bacterium, Endozoicomonas was absent in the E. pallida microbiome. Future work will explore the location of the prokaryotes in and on the anemones, determine the fungal components and use the anemones as coral models in temperature and pH challenges.