Staghorn Corals' Immune System Fights Back

Sherman's Lagoon / KING

Acropora species corals – elkhorn and staghorn – within the Caribbean basin are not in great shape.  I’ve written before of some intriguing research regarding raw sewage and potential links to an increase in white pox disease of these corals.  Yet white pox isn’t the only disease plaguing Caribbean stony corals – white band disease also claims a number of colonies.

PLOS One published a paper today that uncovered white band disease (WBD) resistant genotypes in populations of staghorn growing in reefs near Bocas del Toro, Panama.  Three genotypes from two of four surveyed populations on separate reefs were found to be entirely resistant to WBD while several other genotypes yielded a range of susceptibility to WBD infection. 

That’s pretty amazing.  The authors said it best, I feel:

Evidence for natural disease resistance in a reef-building corals supports growing interest in the role that host resistance might play in buffering the impacts of the global rise in marine diseases on tropical coral reefs and elsewhere.  […]  While it remains to be seen how important and pervasive disease resistance in reef corals might be, its existence demonstrates that some corals have the innate ability and adaptive genetic variation to respond to diseases and possibly other stressors, including coral bleaching. With coral bleaching, strong emphasis has been placed on the role of algal symbiont diversity as a means to respond to bleaching, i.e. the adaptive bleaching hypothesis [62][66]. Like host resistance to disease, we suggest that there is potential for adaptive genetic variation for bleaching resistance within the genomes of corals as well.

Does this mean we can count on the genetic toolbox of Acropora corals to combat the multiple factors involved in their conservation – from increasing water temperatures to coral bleaching to disease?   Probably not.  But given the fact that researchers believe Acropora relies on fragmentation to reproduce relative clones of itself locally, and is a poor sexual recruiter and disperser, the existence of resistant genotypes at all is very encouraging. 

Of course the most interesting result from this would be to survey Acropora colonies from larger areas of the Caribbean against these known resistant microsatellite markers to see if they exist in other populations.  The obvious conservation project seems clear: breed WBD-resistant Acropora larvae and release them to recruitment sites throughout reefs which are practically Acropora-less.  Right? 

Well.. if this study teaches us anything, its that genetic diversity in our threatened species is a seriously good thing and can harbor, of all things, the very solution that can help a species survive one of its current impacts.  If we build projects that generate larvae for release and restoration lets make sure that they aren’t all entirely bred out of the Panama group or we may miss out on other genetic keys to survival. 

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