New host records of scleractinian-Zanclea symbiosis from Fiji

Scleractinian corals are the host group with the greatest number of species associated with hydroids in the genus Zanclea. There are 34 nominal species and 31 genera of scleractinians reported as Zanclea hosts from a few localities across the Red Sea, Indo-Pacific, and Caribbean. However, little is known about how consistent and cosmopolitan scleractinian- Zanclea relationships are. To test their geographical consistency, we surveyed Fijian corals for Zanclea presence using both field-based surveys and analysis of in situ coral photographs. Surveys targeted 16 species and seven genera of reported Zanclea hosts and five other corals commonly found at the sites. We observed Zanclea hydroids associated with 22 species in seven genera of scleractinian corals with 17 (77%) of the species being newly reported hosts. Our findings suggest that a broad diversity of scleractinian corals hosting Zanclea remains to be documented, and although Zanclea -scleractinian associations are likely cosmopolitan in their distribution across localities, associations with specific coral species may not be.