Zebrafish aren't picky when it comes to making friends. A new study reveals that the 3-centimeter-long swimmers—the "lab rats" of aquatic science—will hang around a robotic fish, even a crudely designed one. The robot has features previously shown to attract both male and female zebrafish: the plump round shape of an egg-laden female zebrafish, bright blue stripes in the pattern sported by the species, and a flexible tail that can be moved back and forth. Even though the makeshift model is a whopping five times the size of an adult zebrafish (several shown in background at right), both single zebrafish and groups preferred mingling with the robot to spending time elsewhere in the tank, the researchers report online today in Bioinspiration & Biomimetics. In the dark, however, the zebrafish avoided the robot—a sign, the researchers say, that the fish don't like the noise it makes, but that they're willing to ignore this when they can see the robot's visual cues. The team is now studying how zebrafish and other species respond to free-swimming robots in tanks that include fish of several species, which represents a more realistic environment, and future tests will include vegetation and other hiding spots. Besides helping study fish behavior in the lab, the researchers contend that such robots may offer a way to protect endangered species by luring them away from hazards or by repelling their predators.
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