Walking fish a model of evolution in action

Sometimes, a fish out of water doesn't feel like a fish out of water—at least if it's a Pacific leaping blenny. For the first time, scientists have closely studied the land-dwelling fish, which hops about the rocky coastlines of Micronesia The new study revealed that the "walking" fish are amazingly agile on land, where they engage in complex social and courtship behaviors, study leader Terry Ord, an evolutionary ecologist at the University of New South Wales in Australia, said by email. But Ord and colleagues also found that the landlubbers can forage, court, and mate—basically take care of all their blenny business—only during the few short hours of midtide. That's when the water level is high enough to keep the fish's skin wet but the waves aren't strong enough to carry the animals out to sea. The blennies, which breathe through their gills and partly through their skin, will suffocate if they completely dry out. So "while these fish are very good at living on land ... they are nevertheless very constrained by their evolutionary history," noted Ord, whose study appeared in July in the journal Ethology. "That is, at the end of the day, they are still fish, and fish are more suited to life in water, not on land."