18 Jul 2008

‘This means something… this is important…’

Grunting fish have helped scientists to date the origins of vocal sounds to about 400million years ago. US researchers have found that the area of a fish's brain that drives vocalisation is extremely primitive. Writing in the journal Science, they say it suggests that the ability to communicate through sound emerged very early in the evolution of vertebrates.

The closely related toadfish and midshipman fish are nocturnal, living along the north-west coast of the US and Canada. Professor Bass said: "They make different kinds of sounds in different social contexts. Just as birds will use one call to attract a mate and another call to scare a rival off, the fish do exactly the same thing." A deep hum lures females to a male's nest; a sharp grunt is used to defend territory.

To investigate the origins of vocalisation, the team looked at the area of the fish's brain that was responsible for controlling the pitch and duration of the calls, which is known as vocal patterning.
Professor Bass told BBC News: "We identified where this pattern generator developed in the brains of these fishes, and then we looked at where it was in frogs, birds and primates."
The team discovered that the neural networks for vocalization were all situated in the same region.

"We stood back and said: 'Oh my god, this is all in the same place'. "It was astonishing how similar it was."

The team compared this information with the evolutionary "family tree" for vertebrates. Because the evolution of the fish can be traced back further than that of amphibians, birds and primates, the team was able to deduce when the ability to vocalise came about: "You could see that was a very ancient part of the nervous system shared by all vertebrates.
"We came to the conclusion that it must have evolved early in time before these different groups emerged from the evolutionary family tree - around the time when bony fishes evolved about 400 million years ago." Click title for link to BBC article.