"It was ridiculously high how attracted they were to the beach water," said Dixson. The fish spent more than 99 percent of their time on the side of the chamber with beach water flowing by. "The next step was to figure out what is in the beach water that is making them able to discriminate beach water from the other," she said. Researchers have previously shown that clownfish are attracted to a chemical cue from anemones, and the team found that the fish strongly preferred water that had been exposed to anemones versus water that had not. But the signal from anemones is unlikely to travel very far, so the team wondered whether there were other cues that could draw the fish back to the islands. "The islands are loaded with trees," Dixson explained, and the water nearby has large numbers of leaves floating on the surface. So, the team exposed ocean water to five different kinds of leaves from the islands, and to a mixture of the leaves, and compared those to ocean water with no leaf exposure. "They were attracted to all of them." But they were not attracted to the tea tree plant, which grows in swamps nowhere near the islands, so the fish have specific preferences for the "right" kind of trees. Finally, the team showed that even fish bred in aquariums in synthetic seawater were attracted to beach water and to anemone and leaf cues, suggesting that this attraction is innate. "The results are just spectacular," said Jelle Atema of Boston University who developed the testing chamber for his own research and shared one with the Jones group. "As humans we don't take very seriously the notion of odor in water. It's very foreign to people: How can you smell in water?" Jelle agrees with the researchers that the abundance of leaves in the water near these islands serves to bring the fish into the right vicinity, after which they can search out the anemones. Beyond providing an example of animal abilities, the research also has a broader message. "It shows that there is a connection between the marine and the terrestrial environment," Dixson said. "It shows that the two can't be treated separately, especially in terms of management." "If you're trying to protect the reef, but you're not protecting the shoreline that calls these 'Nemos' home, it's not going to work," she said. Related Links: Jessica Marshall's blog: EnvironMental Case |
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