KĀNEʻOHE, HI [Jan 30]— In the realm of marine biogeography, there is a widely held scientific principle: the Atlantic and Indo-Pacific oceans are worlds apart. If you dive in Brazil and then in Okinawa, you expect to see entirely different groups of fish and coral. But according to a new global study published today in Frontiers of Biogeography , one group of colorful hexacorals, anemone-like creatures—known as zoantharians—is breaking all the rules.
The study, led by Dr. Maria "Duda" Santos of the UH Mānoa Hawaiʻi Institute of Marine Biology (HIMB) ToBo Lab and the University of the Ryukyus , began with a moment of "déjà vu" underwater.
"During my first dive in Okinawa, I was surrounded by a multitude of species I had never seen in my homeland of Brazil. But then I saw the zoantharians. They looked exactly like the ones back home—the same colors, shapes, and sizes. It was striking."
- shares Dr. Santos.
While the Indo-Pacific typically hosts ten times the species diversity of the Atlantic for most reef animals, this research found that the genetic and morphological divergence between oceans for these creatures is surprisingly narrow.
The Secrets of the Ultimate Travelers
The researchers suggest that zoantharians may be the ultimate oceanic travelers. Their secret likely lies in high dispersal via an "epic" larval phase, where young zoantharians can survive in open water for over 100 days, paired with an ability to "raft" across ocean basins by hitchhiking on floating objects. Furthermore, an unusually slow evolutionary rate appears to keep distant populations looking and acting like siblings, even after millions of years of separation by continental barriers.
This discovery has major implications for the future of our oceans. As climate change stresses traditional stony corals, zoantharians are increasingly moving in to fill the void.
"In habitats impacted by stress, some zoantharian species can outcompete stony corals. We are seeing 'phase shifts' where reefs once dominated by corals are being taken over by zoantharians. Understanding how they spread helps us forecast what the reefs of the future will look like."
- explains Dr. Santos.
A Global Atlas for a Changing Ocean
This landmark study represents a massive international effort, uniting a team from Hawai'i, Okinawa, Russia, Brazil, Hong Kong, Taiwan, and Indonesia. By combining DNA data and records from Mexico to the Philippines, the team has provided the first-ever global "atlas" for a group of animals that has remained in the shadows of their more famous coral cousins for decades. This map of the past and present provides a vital baseline for monitoring how marine life will navigate a warming world.
Original source:
Santos, M.E.A., Kise, H., Fourreau, C.J.L., Kiriukhin, B., Kitahara, M.V., Baker, D.M., Toonen, R.J., Liu, P.J., Chang, A., Tu, T.-H., Widiastuti, Agustini, K.M.P., Bowen, B.W. and Reimer, J.D. (2026). Global biogeography of zoantharians indicates a weak genetic differentiation between the Atlantic and Indo-Pacific oceans, and distinct communities in tropical and temperate provinces. Frontiers of Biogeography, 19. doi:https://doi.org/10.21425/fob.19.174247.
