Walk, Don’t Skate: Some Fishes “Walked” Way Before Land Animals Did

Little skates and winter skates are very similar in appearance, but the claspers along this one’s tail would suggest it’s a little skate. Photographed at Cape Ann, Mass.

SCIENTISTS STUDYING A SPECIES OF RAYS CALLED LITTLE SKATES have demonstrated that walking capabilities had developed in fishes dwelling on the seabottom millions of years before the first marine animals climbed out of the oceans to become air-breathing, leg-walking land dwellers.

Click on this screen shot of this little skate’s movements to see the video, created by Cell and posted by Science Magazine. 

And they show how they moved with a video of modern little skates – little skate is the fish’s common name, not just a description – do it, utilizing a set of fins to create movement that resembles walking.

The team of neuroscience specialists was studying the development of genes and nerve cells that made the walking movement possible, exploring the left-right alternation and extension-flexion in their pelvic fin muscles. Their findings are important in the understanding of an important event in evolution.

And their conclusion is that the neural architecture found in little skates and terrestrial vertebrates an even more ancient common ancestor. It’s believed that the first fishes moved onto land some 375 million years ago (mya). It’s believed that the nerves that control walking evolved in fishes some 420 mya.

The team, comprised of neuroscientists from New York University and institutes in Australia and Singapore, reported their findings in the February 8th, 2018 issue of the  journal Cell.

They also released a video explaining their results – Skating into the Evolution of Walking – to help explain the science. Click on the screen shot to connect.

And, here’s a discussion of it by science writer Steph Yin in the New York Times.

ABOUT LITTLE SKATES Little skates (Leucoraja erinacea) are members of the superorder Batoidea, which includes all rays, and the order Rajiformes. There are some 280 species of skates worldwide; L. erinacea is one of about a half-dozen species found along the U.S. mid-Atlantic coast. From the Gulf of Maine south to the Carolinas.

Like most of them, little skates have flattened bodies, eyes on the dorsal side, mouths on the underside, tails and broad pectoral fins formed into “wings,” with which they swim. And, like most of them, they largely live on the seafloor and scrounge for snails, crustaceans, clams and oysters and other small prey.

Although most sources don’t pay attention to it, they also have less visible pelvic fins with which they “walk” on the seabottom.

In appearance, little skates somewhat resemble stingrays (order Myliobatiformes), but without the barb, or stinger on their tails.

ADDITIONAL RESOURCES:  “Primitive fish’s sea-floor shuffle illuminates the origins of walking,  Giorgia Gugliemi, Nature.com, Feb. 8., 2018;  “What We’re Doing to Learn More About Skates,” “Northeast Skate ID Guide,” NOAA; Marine Life of the North Atlantic, Andrew Martinez.

 

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