If you think the dating world is tough for a human, consider for a moment the Nopoli rock-climbing goby of Hawaii, which scales waterfalls up to 100 feet high in order to breed. To put this feat in perspective, it’s the equivalent of a man of average height scaling the 29,029 feet of Mount Everest!
The process leading to this incredible feat is, quite literally, jaw-dropping: the tiny one-inch goby propels itself up the waterfall rocks with two suckers – one, common to all gobies, on the belly, and a second, particular to one goby genus, that develops when the mouth migrates from the tip of its head to its chin over the course of 36 to 48 hours, before it embarks on its journey. The fish uses these dual suckers alternately to inch up the rocky substrate of waterfalls to the waters above where the goby mates and deposits eggs in streams. Upon hatching, these juvenile gobies are swept into the ocean where they develop for several months before they return to freshwater streams and pools upstream where they may live for several years. To mate, the gobies of this new generation must repeat the waterfall-climbing process themselves.
When there’s invading seaweed in your neighborhood, who you gonna call? Well, a new study by scientists at Georgia Tech shows that when corals are threatened by toxic algae they use chemical signals to call for help from their “bodyguards”, the unassuming goby fish.
The study, carried out on coral reefs in Fiji and published in the November 8 issue of the journal Science, shows that within moments of the coral’s “911 call” the gobies respond to these chemical distress signals and pick off the offending seaweed. What’s in it for the fish? Gobies spend their entire lives with the same patch of coral, using it for protection from predators and even feeding on mucus produced by the coral. It comes as little surprise then that the goby takes any threat to its shelter very seriously.
"The fish are getting protection in a safe place to live and food from the coral," said Mark Hay, a biology professor at Georgia Tech and the study’s co-author. "The coral gets a bodyguard in exchange for a small amount of food. It's kind of like paying taxes in exchange for police protection."
For one species of goby, feeding on the toxic algae has the secondary effect of making the fish itself more toxic to predators.
Coral is under threat worldwide from pollution and ocean acidification from human activity. When corals are stressed, aggressive algae competing for sunlit patches of ocean floor can represent a death blow to coral reefs and the magnificent ecosystems they support. At least one fish, though, isn’t letting the reef go down without a fight.