Eye-catching Crustaceans

By Anna Tiley

At first glance the mantis shrimp may seem to be just another brightly coloured marine crustacean but in fact it has an incredible way of visualising the world.

The eyes of a mantis shrimp can see far more than our own and are regarded by some to be the most complex eyes in the entire animal kingdom. Whereas we only see three different colours, a mantis shrimp is able to detect up to twelve, including UV. In addition to this, a mantis shrimp can distinguish between circular, linear and elliptical polarised light, something that we are unable to do.

The eyes themselves are attached to stalks which move independently of each other and scan the horizon for objects. Additionally each eye rotates on its stalk, thereby increasing the field of view. The anatomy of the eye itself is such that the animal can gain all the visual information it needs with only one eye and this could be the reason why both eyes rarely work together.

Although we don’t know why these animals require such a good visual system, some theories suggest that it could help efficient detection of predators, prey and potential mates in the underwater environment.

Image

Current research into how this visual system works has also identified an additional interesting characteristic; on occasion, both eyes do in fact work together.

It was observed that sometimes the eyes rotate with a 90° difference to each other in an anticlockwise direction, almost as if they were both adjusting to the same point.

So what are they doing? The theory is that they may be rotating to get a better view of polarisation. This is quite similar to holding up a polariser for a camera and twisting it in different directions to allow more or less of the light through. It could be possible that the mantis shrimp is rotating both of its eyes to get the best focus on an object by adjusting the amount of polarised light it sees.

This research is particularly exciting as it could have a potential application for developing “intelligent” machines. The mantis shrimp is able to process a huge amount of visual information with only a small brain. It could therefore be possible to apply this visual system to an unmanned vehicle, such as the Curiosity Rover on Mars, enabling it to preprocess visual information and independently identify interesting items for study.

Advertisements