Diversity in symbiotic dinoflagellates (Pyrrhophyta) from seven scleractinian coral species: Restriction enzyme analysis of small subunit ribosomal RNA genes

The diversity of symbiotic dinoflagellates (SD) from seven coral species (Fungia scutaria, Fungia paumotensis, Leptastrea transversa, Pavona cactus, Pocillopora verrucosa, Montastrea curta, and Acropora formosa) was studied in a restricted geographical area, the Lagoon of Arue on the island of Tahiti. Their diversity was explored by small subunit ribosomal RNA gene (SSU rDNA) restriction fragment length polymorphism (RFLP). After a nested amplification with SD specific primers, RFLP analyses were performed directly and after a cloning step. The diversity of these different SSU rDNA was estimated in respect to possible technical artifacts. In an axenic culture of SD from the coral Galaxea fascicularis, both heterogeneous SSU rDNAs and artifact molecules were observed as in our SD samples. According to the number of patterns observed, corals Fungia paumotensis, Leptastrea transversa, Pavona cactus, Montastrea curta, and Acropora formosa contained one class of SD SSU rDNAs, whereas Fungia scutaria and Pocillopora verrucosa contained three and two classes of SD SSU rDNAs respectively. In the limited geographic area studied, SD from different coral species shared the same pattern, except SD from Montastrea curta, which showed a unique pattern. In addition to the possibility of SD flux among different coral species, specific mechanisms could also be involved in the establishment of a symbiosis.