How Just One Nasty Winter Forced This Lizard to Evolve

PiccoloNamek, Wikimedia Commons // CC BY-SA 3.0
PiccoloNamek, Wikimedia Commons // CC BY-SA 3.0

Scientists say a single unusually cold season altered the course of history for one American reptile. The green anoles who survived the winter of 2014 were those who could stand the cold—a trait they passed on to their offspring. The researchers published their findings in the journal Science.

The green anole, Anolis carolensis, also known erroneously as the American chameleon, is a vibrant little lizard that makes its home in the southeastern U.S. and Caribbean. Its range extends from Texas as far north as Oklahoma. This is unusual for reptiles, whose cold-blooded bodies typically restrict them to balmier climates.

Map of the geographic range of the green anole.
Graphic by Julie McMahon

To find out how the anoles were managing it, Shane Campbell-Staton, now of the University of Illinois, paid visits to five scattered populations in 2013. He collected samples and a few live lizards from each group to test their DNA, gene expression, and tolerance for low temperatures.

He found a fair amount of variation between lizard communities. Those in Oklahoma had clearly evolved to handle the weather there, while specimens from further south couldn't take the cold.

Satisfied with his data and findings, Campbell-Staton prepared to wrap up the project.

Then winter came. You may remember the winter of 2014, when a polar vortex created record-breaking low temperatures and wrought terrible storms across the U.S., including in anole territory. Campbell-Staton couldn't help but wonder how—or if—the cold-intolerant lizards had survived.

The next spring and summer, he and his colleagues made another circuit through anole country and collected more samples. The Oklahoma families hadn't fared too poorly. But down south, things had clearly changed. The genetic code of Texan lizards looked more like their northern cousins, and individuals were far better at handling a chill. 

The research team realized that the brutal winter had killed off most of the cold-intolerant lizards, leaving behind only those who happened to have genes more like their northern cousins'. Those lizards reproduced, creating new generations of cold-ready individuals.

But that's not necessarily a good thing.

"One might think, 'Oh, they responded! They're better now,'" Campbell-Staton said in a statement. "But selection always comes at a cost, which is death, basically. It may be that the animals that did not survive this storm had the genetic variants to survive a heat wave, or a drought, or some other extreme event. And now those lineages are essentially gone." 

Middle School Student Discovers Megalodon Tooth Fossil on Spring Break

iStock.com/Mark Kostich
iStock.com/Mark Kostich

A few million years ago, the megalodon was the most formidable shark in the sea, with jaws spanning up to 11 feet wide and a stronger bite than a T. Rex. Today the only things left of the supersized sharks are fossils, and a middle school student recently discovered one on a trip to the beach, WECT reports.

Avery Fauth was spending spring break with her family at North Topsail Beach in North Carolina when she noticed something buried in the sand. She dug it up and uncovered a shark tooth the length of her palm. She immediately knew she had found something special, and screamed to get her family's attention.

Her father recognized the megalodon tooth: He had been searching for one for 25 years and had even taught his three daughters to scour the sand for shark teeth whenever they went to the beach. Avery and her sisters found a few more shark teeth that day from great whites, but her megalodon fossil was by far the most impressive treasure from the outing.

Megalodons dominated seas for 20 million years before suddenly dying out 3 million years ago. They grew between 43 and 82 feet long and had teeth that were up to 7.5 inches long—over twice the size of a great white's teeth. They're thought to be the largest sharks that ever lived.

Megalodon teeth have been discovered on every continent except Antarctica, but they're still a rare find. Avery Fauth plans to keep her fossil in a special box at home.

[h/t WECT]

Watch the Denver Zoo’s New Baby Sloth Cuddle Up With Its Mom

Denver Zoo
Denver Zoo

If you’re a sucker for itty, bitty, furry animals, then you’ll want to drop whatever it is you’re doing and check out this video of the Denver Zoo’s newest resident. Uploaded by The Denver Post, the video shows a week-old sloth clinging to its mother, and it’s almost too cute to handle.

The healthy baby, whose name and sex have not yet been determined, was born on April 11 to its proud sloth parents: 23-year-old Charlotte Greenie and 28-year-old Elliot. It also has an older sister, named Baby Ruth, who was born in January of last year. Dad and Baby Ruth are “temporarily off-exhibit” to give mom and her newborn baby the chance to rest and bond in their habitat—an indoor aviary that's part of the zoo's Bird World exhibit.

The baby belongs to one of six species of sloth called the Linne's two-toed sloth, which is native to the rainforests of South America and are not currently considered threatened. Unlike their distant relatives the three-toed sloths, two-toed sloths are mostly nocturnal creatures. They also tend to move faster than their three-clawed counterparts, although fast is putting it generously.

Like many things sloths do, the baby was slow to arrive. Zoo officials predicted that Charlotte would give birth as early as January, but the expected due date may have been a miscalculation.

“Sloth due dates are notoriously challenging to predict because sloths are primarily active at night and we rarely observe their breeding,” the zoo said in a statement. “Our animal care team closely monitored Charlotte for months to ensure that she and the baby were healthy and gaining the appropriate amount of weight.”

The baby is expected to cling to its mother for at least six months. Zoo officials say the best time to visit mom and baby is in the late afternoon, when Charlotte is more likely to be active.

[h/t The Denver Post]

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