These fins were made for walking, and that’s just what these fish do — thanks to wiring that evolved long before vertebrates set foot on land.
Little skates use two footlike fins on their undersides to move along the ocean floor. With an alternating left-right stride powered by muscles flexing and extending, the movement of these fish looks a lot like that of many land-based animals.
Now, genetic tests show why: Little skates and land vertebrates share the same genetic blueprint for development of the nerve cells needed for limb movement, researchers report online February 8 in Cell. This work is the first to look at the origins of the neural circuitry needed for walking, the authors say.
“This is fantastically interesting natural history,” says Ted Daeschler, a vertebrate paleontologist at the Academy of Natural Sciences in Philadelphia.
“Neurons essential for us to walk originated in ancient fish species,” says Jeremy Dasen, a neuroscientist at New York University. Based on fossil records, Dasen’s team estimates that the common ancestor of all land vertebrates and skates lived around 420 million years ago — perhaps tens of millions of years before vertebrates moved onto land (SN: 1/14/12, p. 12).
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