July 18, 2008

Evolution Sings the Song of Deep Time Courtesy of Toadfish

Research from Cornell University has revealed the origins of song, and it turns out that life has been singing for a very long time.

The study, carried out by Cornell’s Dr. Andrew Bass (fittingly enough), looked at the development of neural circuitry in toadfish, a taxon that diverged from other vertebrates more than 400 million years ago. The study found that the basic nervous controls that allow the toadfish to vibrate its swim bladder in order to produce humming and grunting sounds that the animal uses as mating and aggression calls respectively, is found in all vertebrates from frogs to birds to humans. This evidence points to the rise of this aspect of vertebrate physiology in the last common ancestor shared by all of these taxa.

Song, after a fashion, has been heard on the earth for a very long time, indeed. The study did not find, however, at what point in deep evolutionary time music appreciation arose.

We all sing like fish

By Susan Milius

...Studies of the nervous systems of larval toadfish have revealed brain circuitry similar to that controlling the vocal muscles in frogs, birds and mammals, says Andrew H. Bass of Cornell University.

Vertebrates croak, sing, ribbit and roar using very different muscles. But Bass and his colleagues propose that a basic network of the nerves setting the rhythms and orchestrating those muscles originates in the same area of the brain and spinal column.

With appearances in such a broad sweep of vertebrates, that neural design probably arose in some long-ago ancestor of all these creatures, he and his colleagues report in the July 18 Science...

Analyzing the larvae helps clarify evolutionary relationships, he says. By adulthood, animal neurons have moved around from their embryonic positions.

"This is a beautiful example of sorting out what happened through evolution by looking at the developing brain," says neuroethologist Fabiana Kubke of the University of Auckland in New Zealand.

In the toadfish larvae, Bass and his colleagues found that the vocal neural circuitry originates in a region encompassing parts of both the hindbrain and the spinal column. That's the same basic region that gives rise to vocal circuitry in other vertebrates, the researchers conclude.

To the trained eye of a neuroscientist, similarity of the basic neural circuitries is "quite striking," Kubke says. "They have beautiful data, absolutely beautiful..."
When I was a teenager, I used to go fishing in the Great South Bay frequently off New York's Long Island. Every so often, I’d catch a rather ugly fish that was known locally as a sea robin. When pulled from the water, these homely critters would croak like frogs. I never thought much of it, and generally would just cut the tails off to use for bait. It never occurred to me that I might be doing in the relatives of the planet’s first musicians.

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