Reindeer have adapted to the dim, blue light of the Arctic winter. Alice/Wikimedia Commons , CC BY-SA
Reindeer's noses may not glow red, but these creatures of cold climes have evolved the ability to change the color of their eyes to help them thrive in dark, northern winters. In this Discovery episode, we speak with Glen Jeffery , a professor of neuroscience at the Institute of Opthamology at UCL (University College London) in the U.K., about what makes reindeer eyes truly unique in the animal kingdom.
Most people have seen the gold, glowing eyes of a cat, a raccoon or some other nocturnal animal staring back at them during a nighttime drive. The part of the eye that produces that golden reflection, as Jeffery explains, โis a mirror that lots of animals have called the tapetum lucidum.โ A taptetum helps animals see better in the dark by bouncing light from the back of the eye through the retina a second time. In most mammals, the tapetum is a โstandard golden,โ as Jeffery describes the color, and that color doesnโt change.
Many animalsโ eyes shine in the darkness because of a reflective layer called the tapetum lucidum that is usually gold. Bowlhover/Wikimedia Commons
One day, Jeffery received a box in the mail out of the blue. It contained two jars filled with reindeer eyes from a slaughterhouse in Norway. One jar was labeled summer and one was labeled winter.
โI opened up the summer ones first and I thought, โIโm wasting my time here,โโ says Jeffery. He saw golden eyes, just what he expected.
โBut then we opened up the other eyes, and that was when there was a shock, because the winter eyes were blue,โ he said. โIโd never seen anything like that in my life.โ
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Jeffery and his colleagues spent years studying the biology of reindeer eyes and the environment they are made for โ the dim, blue-hued months of the Arctic winter. What they discovered is a marvelous bit of evolution that has given reindeer some of the most interesting eyes on Earth. Listen to this Discovery episode of the Conversation to hear about how Jeffery and his colleagues study reindeer eyes, why winter eyes are such a unique color and how light pollution can alter this finely tuned adaptation.
This episode was produced by Katie Flood and hosted by Dan Merino. The interim executive producer is Mend Mariwany. Eloise Stevens does our sound design, and our theme music is by Neeta Sarl.
You can find us on Twitter @TC_Audio , on Instagram at theconversationdotcom or via email . You can also sign up to The Conversationโs free daily email here . A transcript of this episode will be available soon.
Listen to โThe Conversation Weeklyโ via any of the apps listed above, download it directly via our RSS feed or find out how else to listen here .
Glen Jeffery receives funding from the Biotechnology and Biological Sciences Research Council of the UK.
This article is republished fromย The Conversation ย under a Creative Commons license.
Beautiful photos of Christmas markets around the world
Tour Christmas markets from around the world
Updated
Dec 4, 2023
Christmas markets are a quintessential holiday tradition in Europe. Countless cities, regardless of size, likely have at least one open-air bazaar that pops up sometime between mid-November and early December to sell holiday tchotchkes and treats.
These advent markets aren't a modern-day invention, either. They've been around for centuries. The first recorded instance dates back to 1298, when vendors in Vienna, Austria, obtained permission to run a December market. Over the next century, these cold-weather fairs increased in popularity, and by 1384 the first Christkindlmarkt opened in Germany.
Originally, the markets sold all of the practical things folks would need to make it through the long cold wintersโmeat, root vegetables, warm textiles, etc.โbut eventually, they began focusing more on special, seasonal items, though the exact timeline of that shift is hard to pin down.
There are now 2,500 to 3,000 Christmas markets ย annually in Germany alone. In anticipation of these and the thousands of other Christmas markets around the world opening up, Stacker compiled a collection of 25 images showcasing some of the most beautiful Christmas markets out there. From historic bazaars to more modern markets, these festivals and their offerings are sure to put you in the holiday spirit.
Rolf Vennenbernd/picture alliance via Getty Images
Budapest, Hungary
Updated
Dec 1, 2023
A newer addition to the Christmas market scene, the Advent Fair at St. Stephen's Basilica in Budapest opened in 2011. Visitors can peruse hundreds of stalls selling handmade wares while admiring the architecture of one of the city's biggest houses of worship.
ATTILA KISBENEDEK/AFP via Getty Images
Berlin, Germany
Updated
Dec 1, 2023
The Gendarmenmarkt Christmas market in Berlin attracts around 800,000 visitors each year. Because of construction, the market has moved to nearby Bebelplatz until 2024.
Meiรner/ullstein bild via Getty Images
Munich, Germany
Updated
Dec 1, 2023
The Christmas market located in front of Munich's town hall is the largest in the German city. In this photo, a traditional Bavarian brass band dressed in lederhosen and dirndl plays during the festival's opening ceremony.
Alexander Hassenstein // Getty Images
Vienna, Austria
Updated
Dec 1, 2023
The Wiener Christkindlmarkt, arguably the most famous Christmas market in Vienna, has roots that date back to the 18th century. The 100-stall festival has only been in its current location in front of Town Hall since 1975 and reportedly sees more than 4 million visitors some years.
JOE KLAMAR/AFP via Getty Images
Strasbourg, France
Updated
Dec 1, 2023
One of the oldest Christmas markets in all of France, Strasbourg's fete dates back to 1570. It's not just the Christkindelsmรคrik that's worth visiting eitherโthe city has dubbed itself the Capital of Christmas and is considered one of the most decorated cities in Europe throughout December.
SEBASTIEN BOZON/AFP via Getty Images
Paris, France
Updated
Dec 1, 2023
The Village de Noรซl at Champs-de-Mars has perhaps some of the best views of any European Christmas market. Stationed at the foot of the Eiffel Tower, the landmark's twinkling lights and holiday displays delight visitors while they enjoy locally sourced food and wine.
Chesnot // Getty Images
Nuremberg, Germany
Updated
Dec 1, 2023
More than 150 stalls at the Nuremberg Christmas market sell goods like mulled wine and handmade holiday decorations.ย It dates back to the 16th centuryย and isย one of the world's oldest and most famous markets.
Johannes Simon // Getty Images
London, England
Updated
Dec 1, 2023
The Winter Wonderland market runs in Hyde Park for six weeks each year, from mid-November to early January.ย Revelers can enjoy amusement park-style rides, food stalls, and boutique shopping.
Tim Graham // Getty Images
Trier, Germany
Updated
Dec 1, 2023
Arranged in front of the Trier Cathedral, Trier's Christmas market has an old-school feel to it. Visitors describe the festival, which has world-renowned mulled wine and historic puppet theater, as "romantic."
Harald Tittel/picture alliance via Getty Images
Rostock, Germany
Updated
Dec 1, 2023
Arguably one of the biggest Christmas markets in Northern Germany, Rostock's festival has run every year since the Middle Ages. Today, the festival has over 3 kilometers of stands with vendors from at least five countries. Over a million guests shop at the market each year.
Bernd Wรผstneck/picture alliance via Getty Images
Cologne, Germany
Updated
Dec 1, 2023
The Christmas Market at Cologne's Alter Markt is geared towards families. Complete with a carousel, Santa's grotto, a puppet theater, and toy stalls, the festival is rumored to be set up by Heinzelmรคnnchen gnomes each year.
Rolf Vennenbernd/picture alliance via Getty Images
Krakow, Poland
Updated
Dec 1, 2023
Traditional wooden stalls line the streets of Old Town during Krakow's annual Christmas market. The bazaar runs from the end of November through Epiphany on Jan. 6 each year.
Beata Zawrzel/NurPhoto via Getty Images
Salzburg, Austria
Updated
Dec 1, 2023
Salzburg's Christmas bazaar, another one of the oldest advent markets in the world, dates back to the 15th century. The festival has been run in its modern form (from the first week of Advent through New Year's Day) since 1974 but still retains plenty of its older traditions.
mikecphoto // Shutterstock
Helsinki, Finland
Updated
Dec 1, 2023
Tuomaan Markkinat is Helsinki's oldest and largest Christmas market. This bazaar closes before the big day (unlike many others on this list). Attendees can peruse nearly 90 vendor stalls under the shadow of the city's most historic buildings.
Finn stock // Shutterstock
Brussels, Belgium
Updated
Dec 1, 2023
While many Christmas markets are content with shopping and food stalls, the Brussels holiday fair offers considerably more. Some of the festival's most prominent attractions are a sound and light show surrounding the centerpiece Christmas tree, an ice skating rink, a Ferris wheel, merry-go-rounds, and a curling rink.
Romy Arroyo Fernandez/NurPhoto via Getty Images
New York, New York
Updated
Dec 1, 2023
Union Square's holiday market opened in 1993 and is modeled loosely on Germany's Christkindlmarkts. Each year millions of visitors stop by to peruse more than 150 stands, whose vendors are all interviewed by organizers before being awarded a highly sought-after slot.
Alexi Rosenfeld // Getty Images
Zagreb, Croatia
Updated
Dec 1, 2023
Zagreb, Croatia, is home to more than 25 Christmas markets, making it feel like the whole city has gotten in the holiday spirit. Start with the one with an ice skating rink in King Tomislav Square and work your way through.
Marco Secchi/Getty Images
Frankfurt, Germany
Updated
Dec 1, 2023
The Frankfurt Christmas market attracts up to 3 million visitors a year and takes place at the Rรถmerberg and the Paulsplatz. More than 100 booths offer mulled wine, winter clothing, and children's rides.
Thomas Lohnes // Getty Images