eye evolution
edyong | March 9, 2010Not Exactly Pocket Science is a set of shorter write-ups on new stories with links to more detailed takes by the world's best journalists and bloggers. It is meant to complement the usual fare of detailed pieces that are typical for this blog.
Cold-proof tongue allows early chameleon to catch early insect
Chameleons are some of the most versatile of lizards. They live in baking deserts and freezing mountaintops and part of their success hinges on a weapon that works just as well in the warmth as in the cold - its tongue. Relying on stored elastic power for its ballistic strike, the…
edyong | October 25, 2009The most incredible eyes in the animal world can be found under the sea, on the head of the mantis shrimps. Each eye can move independently and can focus on object with three different areas, giving the mantis shrimp "trinocular vision". While we see in three colours, they see in twelve, and they can tune individual light-sensitive cells depending on local light levels. They can even see a special type of light - 'circularly polarised light' - that no other animal can.
But Nicholas Roberts from the University of Bristol has found a new twist to the mantis shrimp's eye. It contains a…
edyong | September 16, 2009People with red-green colour blindness find it difficult to tell red hues from green ones because of a fault in a single gene. Their inheritance robs them of one of the three types of colour-sensitive cone cells that give us colour vision. With modern technology, scientists might be able to insert a working copy of the gene into the eye of a colour-blind person, restoring full colour vision.
You might think that the brain and eye would need substantial rewiring to make use of the new hardware, but Katherine Mancuso from the University of Washington thinks otherwise. She has used gene…
edyong | June 2, 2009In the darkness of the deep ocean, some animals create their own light. Among these is the Hawaiian bobtail squid Euprymna scolopes, which forms a partnership with the luminous bacterium Vibrio fischeri. The squid houses colonies of these bacteria in special light organs, and it can control the brightness and direction of their illuminations. But these organs do much more than produce light - they detect it too.
Deyan Tong from the University of Wisconsin has discovered that the organs generate nervous signals when they sense light and they're loaded with proteins responsible for detecting…
edyong | May 21, 2009In the forests of South America lives the unusual but aptly named owl monkey, or douroucouli. You could probably guess by looking at its large round eyes that it's nocturnal, and indeed, it is the only monkey to be mostly active at night. But its eyes have many adaptations for such a lifestyle, beyond a large size.
The owl monkey's retinas are 50% larger than those of a day-living monkey of similar size, like the brown capuchin. The proportions of different cells in their retina are also different. Owl monkeys have relatively few cone cells, which are responsible for colour vision and fewer…
edyong | April 21, 2009Nocturnal animals face an obvious challenge: collecting enough light to see clearly in the dark. We know about many of their tricks. They have bigger eyes and wider pupils. They have a reflective layer behind their retina called the tapetum, which reflects any light that passes through back onto it. Their retinas are loaded with rod cells, which are more light-sensitive than the cone cells that allow for colour vision.
But they also have another, far less obvious adaptation - their rod cells pack their DNA in a special way that turns the nucleus of each cell into a light-collecting lens.…
edyong | February 8, 2009This is the first of eight posts on evolutionary research to celebrate Darwin's bicentennial.
If you were a designer tasked with creating a machine for collecting and processing light, the last thing you would come up with is the human eye. Darwin marvelled at the eye as an "organ of extreme perfection", but in this, he was wrong. Aside from the many illusions that can fool them, our eyes have a major structural flaw. In humans and other back-boned animals, the light-sensing cells of the eye - the "photoreceptors" lie at the back of the retina.
In front of these sensors lie several…
edyong | December 30, 2008In the twilit waters of the deep ocean, beneath about 1000m of water, swims the brownsnout spookfish (Dolichopteryx longipes). Like many other deep-sea fish, the spookfish is adapted to make the most of what little light penetrates to these depths, but it does so with some of the strangest eyes in the animal kingdom.
For a start, each eye is split into two connected parts, so the animal looks like it actually has four. One half points upwards and gives the spookfish a view of the ocean above. The other points downwards into the abyss below and it's this half that makes the spookfish unique.…
edyong | October 24, 2008
Evolution mostly involves small, gradual changes, and for good reason - we might expect that large changes to an animal's genetic code, and therefore to its body plan, simply wouldn't work. It would be like shoving an extra cog into a finely-tuned machine and expecting it to fit in - the more likely outcome is a malfunctioning mess.
But that's not always the case, at least not for the evolution of the human eye. New research shows that the eye and its connections to the brain are surprisingly flexible, and can incorporate major evolutionary changes with ease.
In our retinas, cone cells…
edyong | July 9, 2008Imagine watching a movie where every now and then, key frames have been cut out. The film seems stilted and disjointed and you have to rely on logic to fill in the gaps in the plots. Evolutionary biologists face a similar obstacle when trying to piece together how living species arose from their common ancestors. It's like watching a film with a minimum of footage; the species alive today are just a few frames at the very end, and the fossil record represents a smattering of moments throughout the film's length.
But the gaps, while plentiful, are being slowly filled in. With amazing…
edyong | June 16, 2008Jellyfish may seem like simple blobs of goo, but some are surprisingly sophisticated. The box jellyfish (Tripedelia cystophora), for example, is a fast and active hunter and stalks its prey with the aid of 24 fully functioning eyes. These are grouped into four clusters called rhopalia, which lie on each side of its cube-like body. Together, they give the box jellyfish a complete 360 degree view of its world and make it highly manoeuvrable.
Each eye cluster, four eyes are merely pits containing light-sensitive pigments, but two are remarkably advanced and carry their own lenses, retinas and…
edyong | May 1, 2008
Ultraviolet (UV) radiation lies beyond the violet end of the rainbow. Our eyes aren't equipped to see it and its presence only becomes visually apparent when enough of it hits our skin and causes a painful, red patch - a sunburn. But not all animals have eyes that are so ill-equipped. The females of the jumping spider Phintella vittata not only see UV light, they also find it sexy.
UV light may be invisible to us but many animals can see it and use it to communicate. Sometimes, this is deliberate, as in the case of blue tits using UV patches to seduce females. It can also be…
edyong | March 21, 2008Eagles may be famous for their vision, but the most incredible eyes of any animal belong to the mantis shrimp. Neither mantises nor shrimps, these small, pugilistic invertebrates are already renowned for their amazingly complex vision.
Now, a group of scientists have found that they use a visual system that's never been seen before in another animal, and it allows them to exchange secret messages.
Mantis shrimps are no stranger to world records. They are famous for their powerful forearms, which can throw the fastest punch on the planet. The arm can accelerate through water at up to 10,000…