BBC Homepage World Service Education
BBC Homepagelow graphics version | feedback | help
BBC News Online
 You are in: Sci/Tech
Front Page 
UK Politics 
Talking Point 
In Depth 

Dr Carol Diebel
The crystals point the trout in the right direction
 real 28k

Wednesday, 19 July, 2000, 18:10 GMT 19:10 UK
Trout follow their noses
Trout BBC
By BBC News Online's Matt McGrath

Researchers in New Zealand say they have discovered crystals in the noses of rainbow trout that act as direction finders for the fish.

The tiny crystals are made of magnetite, an oxide of iron that has magnetic properties.

The crystals are linked to individual receptor cells in the brain, allowing the trout to sense changes in magnetic fields.

If I was a fisherman I probably wouldn't invest a large amount of money in a big magnet

Dr Carol Diebel
The work has been carried out by Dr Carol Diebel, curator of marine biology collections at the Auckland Museum, and colleagues. The research is published in the journal Nature.

Dr Diebel says the fish definitely respond to changing magnetic field lines but they are not overpowered by it.

"It is not a huge sense, the magnetic sense," she told BBC News Online. "We think of it more as being supportive. It helps the other senses, and it helps the animal go in the right direction.

"But it doesn't hit them over the head, it just gives them a little nudge."

Flipping Poles

In previous research, she traced a nerve from the brain to a cell in the trout's nose. She was convinced that magnetite crystals existed within the cell. Now, using a powerful laser-scanning microscope, she has found the crystals arranged in a one-micron (millionth of a metre) chain formation.

"What we did was use the laser to focus into the cell, and the beam flares off the crystal surface - it appears larger than it really is and we can see it," Dr Diebel said.

Using a different type of microscope, she then proved that the crystals had magnetic properties.

Trout BBC
"We could get them to flip their poles from north to south when we changed the field around them - you can actually get the crystals to almost twinkle under the scope for you."

So could this knowledge about the trout's magnetic nose be of use to a wily angler? Dr Diebel doubts it.

"We're not saying that rainbow trout are necessarily attracted to magnetic fields, we're just saying that they can use it. So if I was a fisherman, I probably wouldn't invest a large amount of money in a big magnet."

She believes that scientists are on the verge of discovering a general magnetic receptor system in several different animal species.

Work is going on with pigeons and turtles. Magnetic direction finding is also being studied in relation to whale strandings.

Search BBC News Online

Advanced search options
Launch console
See also:

30 Sep 99 | Sci/Tech
Spiders light the way
16 Mar 00 | Sci/Tech
Concorde sends pigeons off course
12 Nov 98 | Sci/Tech
The wheel truth about hamsters
Internet links:

The BBC is not responsible for the content of external internet sites

Links to more Sci/Tech stories are at the foot of the page.

E-mail this story to a friend

Links to more Sci/Tech stories