Analysis of cp23S domain V to assess zooxanthellar diversity among clionaid sponges from Caribbean and Pacific reefs

Among the Porifera, zooxanthellae (genus Symbiodinium) are primarily restricted to several species in the family Clionaidae. Using domain V of cp23S rDNA, we surveyed zooxanthellar diversity in several species from the Florida Keys, Caribbean, and greater Indo- Pacific regions. We examined eight species of sponge (including Cliona varians, C. caribbaea, C. pulvitumulus sp. nov., C. orientalis, C. julieni, C. caesia, Cervicornia cuspidifera, and an unidentified non-clionaid sponge). Key findings included that all Floridian sponges examined harbored G clade zooxanthellae. These zooxanthellae appear to be habitat generalists, with broad environmental tolerances. Belizean and Floridian C. caribbaea harbored A and G clades respectively. Our results indicate that each of the three Indo-Pacific sponges harbored distinct clades of zooxanthellae (A, C and G). This is the first report of C clade zooxanthellae from sponges. A monophyletic, sponge-specific G lineage was discovered in our analysis that is distinct from another G clade group made up of Symbiodinium that associate with foraminiferan hosts. Analysis of secondary structure provided insights into distinct molecular signatures for each clade. Truncated cp23S rDNA domain V molecules were uncovered in C. varians alone