{"169591":{"#nid":"169591","#data":{"type":"news","title":"Corals Attacked by Toxic Seaweed Use Chemical 911 to Summon Help","body":[{"value":"\u003Cp\u003ECorals under attack by toxic seaweed do what anyone might do when threatened \u2013 they call for help. A study reported this week in the journal \u003Cem\u003EScience\u003C\/em\u003E shows that threatened corals send signals to fish \u201cbodyguards\u201d that quickly respond to trim back the noxious alga \u2013 which can kill the coral if not promptly removed.\u003C\/p\u003E\u003Cp\u003EScientists at the Georgia Institute of Technology have found evidence that these \u201cmutualistic\u201d fish respond to chemical signals from the coral like a 911 emergency call \u2013 in a matter of minutes. The inch-long fish \u2013 known as gobies \u2013 spend their entire lives in the crevices of specific corals, receiving protection from their own predators while removing threats to the corals.\u003C\/p\u003E\u003Cp\u003EThis symbiotic relationship between the fish and the coral on which they live is the first known example of one species chemically signaling a consumer species to remove competitors. It is similar to the symbiotic relationship between Acacia trees and mutualist ants in which the ants receive food and shelter while protecting the trees from both competitors and consumers.\u003C\/p\u003E\u003Cp\u003E\u201cThis species of coral is recruiting inch-long bodyguards,\u201d said Mark Hay, a professor in the School of Biology at Georgia Tech. \u201cThere is a careful and nuanced dance of the odors that makes all this happen. The fish have evolved to cue on the odor released into the water by the coral, and they very quickly take care of the problem.\u201d\u003C\/p\u003E\u003Cp\u003EThe research, supported the National Science Foundation, the National Institutes of Health and the Teasley Endowment at Georgia Tech, was reported November 8 in the journal \u003Cem\u003EScience\u003C\/em\u003E. The research was done as part of a long-term study of chemical signaling on Fiji Island coral reefs aimed at understanding these threatened ecosystems and discovering chemicals that may be useful as pharmaceuticals.\u003C\/p\u003E\u003Cp\u003EBecause they control the growth of seaweeds that damage coral, the importance of large herbivorous fish to maintaining the health of coral reefs has been known for some time. But Georgia Tech postdoctoral fellow Danielle Dixson suspected that the role of the gobies might be more complicated. To study that relationship, she and Hay set up a series of experiments to observe how the fish would respond when the coral that shelters them was threatened.\u003C\/p\u003E\u003Cp\u003EThey studied \u003Cem\u003EAcropora nasuta\u003C\/em\u003E, a species in a genus of coral important to reef ecosystems because it grows rapidly and provides much of the structure for reefs. To threaten the coral, the researchers moved filaments of \u003Cem\u003EChlorodesmis fastigiata\u003C\/em\u003E, a species of seaweed that is particularly chemically toxic to corals, into contact with the coral. Within a few minutes of the seaweed contacting the coral, two species of gobies \u2013 \u003Cem\u003EGobidon histrio\u003C\/em\u003E and \u003Cem\u003EParagobidon enchinocephalus\u003C\/em\u003E \u2013 moved toward the site of contact and began neatly trimming away the offending seaweed.\u003C\/p\u003E\u003Cp\u003E\u201cThese little fish would come out and mow the seaweed off so it didn\u2019t touch the coral,\u201d said Hay, who holds the Harry and Linda Teasley Chair in Environmental Biology at Georgia Tech. \u201cThis takes place very rapidly, which means it must be very important to both the coral and the fish. The coral releases a chemical and the fish respond right away.\u201d\u003C\/p\u003E\u003Cp\u003EIn corals occupied by the gobies, the amount of offending seaweed declined 30 percent over a three-day period, and the amount of damage to the coral declined by 70 to 80 percent. Control corals that had no gobies living with them had no change in the amount of toxic seaweed and were badly damaged by the seaweed.\u003C\/p\u003E\u003Cp\u003ETo determine what was attracting the fish, Dixson and Hay collected samples of water from locations (1) near the seaweed by itself, (2) where the seaweed was contacting the coral, and (3) from coral that had been in contact with the seaweed \u2013 20 minutes after the seaweed had been removed. They released the samples near other corals that hosted gobies, which were attracted to the samples taken from the seaweed-coral contact area and the damaged coral \u2013 but not the seaweed by itself.\u003C\/p\u003E\u003Cp\u003E\u201cWe demonstrated that the coral is emitting some signal or cue that attracts the fish to remove the encroaching seaweed,\u201d Hay said. \u201cThe fish are not responding to the seaweed itself.\u201d\u003C\/p\u003E\u003Cp\u003ESimilar waters collected from a different species of coral placed in contact with the seaweed did not attract the fish, suggesting they were only interested in removing seaweed from their host coral.\u003C\/p\u003E\u003Cp\u003EFinally, the researchers obtained the chemical extract of the toxic seaweed and placed it onto nylon filaments designed to stimulate the mechanical effects of seaweed. They also created simulated seaweed samples without the toxic extract. When placed in contact with the coral, the fish were attracted to areas in which the chemical-containing mimic contacted the coral, but not to the area contacting the mimic without the chemical. \u0026nbsp;\u003C\/p\u003E\u003Cp\u003EBy studying the contents of the fish digestive systems, the researchers learned that one species \u2013 \u003Cem\u003EGobidon histrio\u003C\/em\u003E \u2013 actually eats the noxious seaweed, while the other fish apparently bites it off without eating it. In the former, consuming the toxic seaweed makes the fish less attractive to predators.\u003C\/p\u003E\u003Cp\u003EThe two species of fish also eat mucus from the coral, as well as algae from the coral base and zooplankton from the water column. By defending the corals, the gobies are thus defending the home in which they shelter and feed.\u003C\/p\u003E\u003Cp\u003E\u201cThe fish are getting protection in a safe place to live and food from the coral,\u201d Hay noted. \u201cThe coral gets a bodyguard in exchange for a small amount of food. It\u2019s kind of like paying taxes in exchange for police protection.\u201d\u003C\/p\u003E\u003Cp\u003EAs a next step, Hay and Dixson would like to determine if other species of coral and fish have similar symbiotic relationships. And they\u2019d like to understand more about how the chemical signaling and symbiotic relationship came into being.\u003C\/p\u003E\u003Cp\u003E\u201cThese kinds of positive interactions needs to be better understood because they tell us something about the pressures that have gone on through time on these corals,\u201d said Hay. \u201cIf they have evolved to signal these gobies when a competitor shows up, then competition has been important throughout evolutionary time.\u201d\u003C\/p\u003E\u003Cp\u003ECITATION: Danielle L. Dixson and Mark E. Hay, Corals chemically signal mutualistic fishes to remove competing seaweeds, Science (2012).\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research has been supported by the National Science Foundation (NSF) under grant OCE-0929119 and by the National Institutes of Health under grant U01-TW007401. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the NSF or the NIH.\u003C\/em\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia\u0026nbsp; 30332-0181\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E)\u003Cbr \/\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Bodyguard Fish Respond to Signals from Seaweed"}],"field_summary":[{"value":"\u003Cp\u003ECorals under attack by toxic seaweed do what anyone might do when threatened \u2013 they call for help. A study reported this week in the journal \u003Cem\u003EScience\u003C\/em\u003E shows that threatened corals send signals to fish \u201cbodyguards\u201d that quickly respond to trim back the noxious alga.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"A new study shows that coral under attack by seaweed sends chemical signals that attract fish."}],"uid":"27303","created_gmt":"2012-11-08 12:21:18","changed_gmt":"2016-10-08 03:13:10","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2012-11-08T00:00:00-05:00","iso_date":"2012-11-08T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"169551":{"id":"169551","type":"image","title":"Mutualistic fish","body":null,"created":"1449178968","gmt_created":"2015-12-03 21:42:48","changed":"1475894806","gmt_changed":"2016-10-08 02:46:46","alt":"Mutualistic fish","file":{"fid":"195675","name":"mutualistic-fish-goby-coral-alga.jpg","image_path":"\/sites\/default\/files\/images\/mutualistic-fish-goby-coral-alga_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/mutualistic-fish-goby-coral-alga_0.jpg","mime":"image\/jpeg","size":1523275,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/mutualistic-fish-goby-coral-alga_0.jpg?itok=d3b6HGqT"}},"169561":{"id":"169561","type":"image","title":"Mutualstic fish2","body":null,"created":"1449178968","gmt_created":"2015-12-03 21:42:48","changed":"1475894806","gmt_changed":"2016-10-08 02:46:46","alt":"Mutualstic fish2","file":{"fid":"195676","name":"mutualistic-fish42.jpg","image_path":"\/sites\/default\/files\/images\/mutualistic-fish42_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/mutualistic-fish42_0.jpg","mime":"image\/jpeg","size":2492598,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/mutualistic-fish42_0.jpg?itok=5MLbdSQg"}},"169571":{"id":"169571","type":"image","title":"Mutualistic fish - panorama","body":null,"created":"1449178968","gmt_created":"2015-12-03 21:42:48","changed":"1475894809","gmt_changed":"2016-10-08 02:46:49","alt":"Mutualistic fish - panorama","file":{"fid":"195677","name":"mutualistic-fish-panorama30.jpg","image_path":"\/sites\/default\/files\/images\/mutualistic-fish-panorama30_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/mutualistic-fish-panorama30_0.jpg","mime":"image\/jpeg","size":1578677,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/mutualistic-fish-panorama30_0.jpg?itok=EssyTknq"}},"169581":{"id":"169581","type":"image","title":"Mutualstic fish3","body":null,"created":"1449178978","gmt_created":"2015-12-03 21:42:58","changed":"1475894809","gmt_changed":"2016-10-08 02:46:49","alt":"Mutualstic fish3","file":{"fid":"195678","name":"mutualistic-fish-gobidon.jpg","image_path":"\/sites\/default\/files\/images\/mutualistic-fish-gobidon_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/mutualistic-fish-gobidon_0.jpg","mime":"image\/jpeg","size":1044917,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/mutualistic-fish-gobidon_0.jpg?itok=xy65Lsod"}}},"media_ids":["169551","169561","169571","169581"],"groups":[{"id":"1183","name":"Home"}],"categories":[{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"}],"keywords":[{"id":"7166","name":"coral"},{"id":"11994","name":"Fiji Islands"},{"id":"13884","name":"Mark Hay"},{"id":"49611","name":"mutualistic fish"},{"id":"169448","name":"seaweed"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"id":"39541","name":"Systems"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News \u0026amp; Publications Office\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}