July 18, 2008

Scientists Study The Evolution Of Social Communication In Fish

Scientists reported in Friday's edition of the journal Science, that toadfish use special songs to attract their mates.

Now, researchers are using the discovery to delve into the study of how animals use vocalized hums, chirps and whistles to communicate with one another.

It is well documented that animals like birds, frogs and even whales use sounds to convey different messages, but by comparing the nerve networks in a variety of vertebrates researchers suggest that making sounds originated in ancient fishes.

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

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

He said that the nervous system which allows for the creation of speech actually originated in fish hundreds of millions of years ago.

Professor Bass 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," he said.

Bass and his colleagues noted two major functions for the use of sound in animals.

One is the hum in which the male sings to attract the female to his nest, which Bass likened to 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."


Image Caption: Midshipman fish shown inside their nest in the rocky intertidal zone of northern California. There are newly fertilized eggs and larvae on the "roof" of the nest. Photo credit: Margaret Marchaterre, Department of Neurobiology and Behavior, Cornell University.


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