Reindeers’ eye colour season-dependent / News / The Foreigner

Reindeers’ eye colour season-dependent. ‘Rudolph’s’ eyes are deep blue in winter and green-gold in summer, biologists at three academic and medical institutions find thanks to Norway’s Sami. As previously reported, the reindeer is a very environment-adaptive animal, with its nose turning red to help regulate brain temperature. Now, it has been discovered that the animal is well-suited to coping with light conditions farther north. “Unique” Their eyes are like those of a cat when reflecting light. It is not believed any other animal possesses this quality.

saminorway, reindeer, arcticcircle



The Foreigner Logo

The Foreigner is an online publication for English speakers living or who have an interest in Norway. Whether it’s a glimpse of news or entertainment you’re after, there’s no need to leave your linguistic armchair. You don’t need to cry over the demise of the English pages of Aftenposten.no, The Foreigner is here!

Norske nyheter på engelsk fra Norge. The Foreigner er en engelskspråklig internett avis for de som bor eller som er interessert i Norge.

Google+ Google+ Twitter Facebook RSS RSS



News Article

LATEST:

}

Reindeers’ eye colour season-dependent

Published on Monday, 23rd December, 2013 at 10:49 under the news category, by Michael Sandelson   .
Last Updated on 23rd December 2013 at 11:00.

‘Rudolph’s’ eyes are deep blue in winter and green-gold in summer, biologists at three academic and medical institutions find thanks to Norway’s Sami.

Reindeer herding
The Sami have herded reindeer for centuries. This picture is taken in Sweden.Reindeer herding
Photo: Mats Andersson/Wikimedia Commons


As previously reported, the reindeer is a very environment-adaptive animal, with its nose turning red to help regulate brain temperature. Now, it has been discovered that the animal is well-suited to coping with light conditions farther north.

“Unique”

Their eyes are like those of a cat when reflecting light. It is not believed any other animal possesses this quality.

“Our study shows that the reindeer’s eyes are specially adapted to the lighting conditions that characterize high latitudes. This has never been reported before, because no one has looked at animals that experience extreme light conditions throughout the year,” said Professor Karl-Arne Stokkan at the University of Tromsø’s (UiT)  Department of Arctic and Marine Biology.

According to him, the mechanism is designed to cope with the winter twilight, very prevalent north of the Arctic Circle for several months of the year.

Reindeer, like many animals, have a tapetum lucidum (TL) – which translates from Latin to “bright carpet”. It is a light-reflecting surface behind the retina.

Pressure build-up

The TL, which is what alters the colour of reindeers’ eyes, helps nocturnal animals see in the dark as it bounces light back inside the eye. In this way, the eye gets more time to stimulate the retina’s light-sensitive receptors.

In the eye is a cellular pump, pushing fluid into the eye. Fluid can only escape thanks to a drainage system located behind the eye. However, the TL seems to cover the drainage system when the animal’s pupils are considerably expanded in the dark. In this way, pressure in the eye increases.

Although pressures increase in humans’ eyes at night to a certain extent, “the pressures we have measured in the reindeer eye in winter are so high that they would be harmful in the human eye,” stated Professor Stokkan.

Pros and cons           

“The fibres in the reindeer’s tapetum are brought closer together because of this pressure, which changes the colour of the reflected light. This means that the eye’s light sensitivity is increased, because blue light is scattered more than yellow light,” he further explained.

Reflecting the blue light has a disadvantage, though, as the image becomes blurred and visual sharpness reduced. At the same time, though, the upside is that reindeer can detect predators more easily as it makes the animal considerably more sensitive to movement in the winter shadows.

The animals can take advantage of their sharper vision in the bright summer months, whilst in winter they become glaucomic from a medical point of view, according to the researchers.

“I was considerably shocked”

“Reindeer herders are very familiar with this phenomenon. They say that if you stand still just a short distance from a herd of reindeer in the winter, they won’t see you, but as soon as you move the animals startle and run away,” said Professor Stokkan.

In order to conduct the research, biologists collected eyes during the summer and winter from reindeer felled by the Sami.

Glen Jeffery, Juliet Dukes, and Stephen C. Dakin at University College London’s Institute of Ophthalmology also contributed.

“That first time, they [the indigenous herders] sent me 10 eyes from summer and 10 eyes from winter. When I opened them, I had the biggest shock I've ever had in science. The winter ones were clearly blue and the summer ones clearly gold. I wished I had someone sitting next to me to exclaim to,” remarked Professor Jeffery.

Up until then, scientists had always assumed the eye colour was fixed.

Limited market

The study, published in The Proceedings of the Royal Society B, is funded by a grant of two million kroner (some 198,200 pounds sterling) from the British Research Council.

Moorefields Eye Hospital’s Magella Neveu and Chris Hogg co-contributed, as did Professor Karl-Arne Stokkan’s fellow University of Tromsø, Department of Arctic and Marine Biology colleagues Lars Folkow and Sandra Siefken.

Professor Stokkan describes what was carried out as “curiosity-driven research”, but with no immediate practical application.

“Our finding that a reindeer’s eye colour can change may also hold true for other animals. But we were the first to discover this, as well as the first to discover that large mammals have ultraviolet vision,” he said.

“An extensive amount of research has now been conducted in this field, and initial results suggest that only humans and some species of monkeys cannot see UV light. All other animals can see it,” concluded the Professor.




Published on Monday, 23rd December, 2013 at 10:49 under the news category, by Michael Sandelson   .
Last updated on 23rd December 2013 at 11:00.

This post has the following tags: saminorway, reindeer, arcticcircle.





  
Do NOT follow this link or you will be banned from the site!