Archer fish can see like mammals (w/ Video)

Sep 15, 2010 by Lin Edwards report
Banded archerfish, Toxotes jaculatrix. Image: by R.Wampers, via Wikipedia

(PhysOrg.com) -- The ability to see objects oriented differently to the background, which is known as orientation-based saliency, has long been thought to be confined to mammals, but a new study has found that archer fish have this ability, despite having no visual cortex in their brains.

Orientation saliency means objects aligned differently to the background appear to “pop out” from it. In humans this ability is controlled by neural pathways in the , and helps in identifying important objects in the visual field.

Archer fish (Toxotes jaculatrix) catch insects moving on tree branches or flying above by accurately spitting a jet of water at them to knock them into the water. They also accurately determine the falling insect’s trajectory to determine exactly where it will hit the water. Their abilities are so impressive that researchers from the Ben Gurion University of the Negev in Israel wondered if they exhibited orientation saliency as well.

The researchers, led by computer scientist Ohad Ben-Shahar, trained five archer fish to shoot at images of insects on an LCD screen above their tanks. They then replaced the images of insects with a series of images of two bars representing prey objects set against a patterned background representing the habitat. The bars were shown either both oriented in the same direction as the background pattern, both perpendicular to the pattern, or with one bar in each direction.

This video is not supported by your browser at this time.
A sample experimental trial from the experiment. Video credit: Alik Mokeichev.

The researchers observed which bar the fish detected and shot at each time and found they shot most often at bars oriented perpendicular to the background pattern, suggesting these objects were most obviously visible to them. They then tested humans with the same stimuli, and found that they too were most likely to pick out the bars aligned perpendicular to the background. These results suggest the archer fish have orientation-based saliency as humans do.

The fact that archer fish have no visual cortex means the neural mechanism may be similar to that in mammals, but located elsewhere in the , or there may be a completely different mechanism. So far, the neural pathways are unknown in the archer fish.

The study also raises the question of whether orientation salience evolved differently in fish and , or evolved only once in an ancient common ancestor, and has been conserved for millions of years because of its usefulness. The ability may also be much more widespread than previously thought.

The paper was published in the Proceedings of the National Academy of Sciences (PNAS).

Explore further: Researchers discover the most effective animal signal strategies

More information: Orientation saliency without visual cortex and target selection in archer fish, Alik Mokeichev et al., PNAS, Published online before print September 13, 2010, doi:10.1073/pnas.1005446107

Related Stories

Fish can recognize a face based on UV pattern alone

Feb 25, 2010

Two species of damselfish may look identical -- not to mention drab -- to the human eye. But that's because, in comparison to the fish, all of us are essentially colorblind. A new study published online on ...

Recommended for you

New critter discovered on whale carcass

18 hours ago

A new species of bug, similar in appearance to the common woodlouse, has been found plastered all over a whale carcass on the floor of the deep Southern Ocean.

Some cows' infertility linked to Y chromosome

20 hours ago

In the beef industry, if a cow does not get pregnant after breeding, she becomes an economic liability in the herd. Lack of calf production can significantly reduce annual revenue for producers.

User comments : 0

More news stories

Rainbow trout genome sequenced

Using fish bred at Washington State University, an international team of researchers has mapped the genetic profile of the rainbow trout, a versatile salmonid whose relatively recent genetic history opens ...

New critter discovered on whale carcass

A new species of bug, similar in appearance to the common woodlouse, has been found plastered all over a whale carcass on the floor of the deep Southern Ocean.

Mantis shrimp stronger than airplanes

(Phys.org) —Inspired by the fist-like club of a mantis shrimp, a team of researchers led by University of California, Riverside, in collaboration with University of Southern California and Purdue University, ...

Volitional control from optical signals

(Medical Xpress)—In their quest to build better BMIs, or brain-machine-interfaces, researchers have recently begun to look closer at the sub-threshold activity of neurons. The reason for this trend is that ...