Scientists trace development of vocalization using toadfish

WASHINGTON -- It's not exactly Tony serenading Maria in "West Side Story," but for all their homeliness toadfish also sing to attract mates.

OK, singing may be a stretch; it's more of a hum. But it turns out to be useful, for science as well as the fish. Exploring how their nervous system produces sounds is allowing scientists to trace the earliest developments of vocalization in other animals, including people.

Many animals communicate vocally -- birds chirp, frogs thrum, whales whistle -- and comparing the nerve networks in a variety of vertebrates suggests that making sounds originated in ancient fishes, researchers report in today's edition of the journal Science.

The sounds of whales and dolphins are well known, but most people don't realize fish also make sounds, lead researcher Andrew H. Bass of Cornell University said in a telephone interview. He's a professor of neurobiology and behavior.

"I'm not saying fish have a language or are using higher powers of the brain," he added quickly. "But some of the networks of neurons, nerve cells in the brain, are very ancient."

The whole nervous system basis that led to speech originated in fish hundreds of millions of years ago, he said.

He studied the hindbrain in the larvae of midshipmanfish and toadfish, which grow up to produce more than one type of sound.

"It's not as complex as what you hear mammals and birds doing; it's the simplest type of communication ... but the parts of the nervous system that generate sounds are easiest to study in these fish," Bass said.

His team found two major uses of sound.

One is the hum in which the male sings to attract the female to his nest. Bass characterized it as like the drone of bees or a motor running.

The second type is a threat sound, more of a grunt or growl, to protect nesting territory.

The locations of the vocal nerves described in the study are consistent with the organization of the vocal systems in frogs, birds and mammals, supporting the idea of a common early development, Daniel Margoliash and Melina E. Hale of the University of Chicago comment in a perspective on Bass's study.

However, they add: "The story of the evolution of vocalizations is still being written, both for its deep ancestral roots and for its most modern development."

The research was funded by the National Science Foundation and the National Institutes of Health.