Periophalmus barbarus

You know the old saying -- like a fish out of water. Well don't be to quick to judge, because some fish, such as the mud skippers, can be right at home in the terrrestial/atmospheric habitat. (At least on the edge of it). This unknown is the blue spotted mud skipper, Periophalmus barbarus, a common fish of the mangrove swamps of the Indo-Pacific region. These small fish (up to about 12 cm in length) are perhaps more at home out of the water than in it. They scurry around the semi-dry sections of the mangrove habitat, and can even climb trees. They search out insect and crustacean food.

Fish that live partially out of the water need to constantly wet their eyes. Our little animation of the eye-wetting action was taken from our video, Branches on the Tree of Life: Chordates, where we take a close look at the mudskipper as a model for how ancient fish ancestors invaded the land. They move about on land by walking, alternatey using their pelvic and pectoral fins. No doubt, there were ancient ancestral fish to all modern land-dwelling vertebrates that also evolved a way to use their fins for walking on land. Mud skippers must also keep their gills wet, and the film of water acts as an interface for the absorption of oxygen - allowing the mud skipper to effectively breathe air. By returning to the water at regular intervals, the mud skipper replenishes the vital fluids that allow it to be a successful fish out of water.