The Tardigrade’s Extraordinary Weirdness Continues

Image credit: Aziz Aboobaker, Edinburgh
Image credit: Aziz Aboobaker, Edinburgh

The mystery of the tardigrade—a.k.a. moss piglet, a.k.a. water bear—is one step closer to a solution. Scientists studying the microscopic animals' DNA say the tough, many-legged creatures may be distantly related to nematodes and other "wormy things." The researchers published their findings in the journal PLOS Biology.

Tardigrades are some of the strangest, most badass organisms on Earth. Don't be fooled by their tiny size—these animals are anything but delicate. They can survive in the most brutal conditions, from dehydration and starvation to burning heat, blistering cold, intense radiation, and even the vacuum of space.

How they pull off this near-invincibility is, naturally, a question of some interest among biologists (and to Mental Floss—links to our many articles about these amazing creatures are found throughout this story).

The authors of one 2015 study made headlines when they announced that one-sixth of the tardigrade's genetic blueprint had been swiped from bacteria and other organisms. This horizontal gene transfer (HGT) is not unheard of in nature, but other tardigrade experts, including a team at the University of Edinburgh, felt that 17.5 percent seemed suspiciously high, even for a maverick like the tardigrade.

The skeptics were right. Additional investigation into the tardigrade genome confirmed the presence of a few horizontally transferred genes. Just a few.

HGT aside, there's still plenty to discover in the tardigrade's genes. Tardigrades have been tardigrades for hundreds of millions of years. No fossils remain from their early days to tell us what they might have been before. We don't really know where they came from, evolutionarily speaking, or who their relatives are.

To find out, Edinburgh researcher Mark Blaxter and his colleagues picked apart the genomes of two tardigrade species, Ramazzottius varieornatus and Hypsibius dujardini. They found something unexpected: The armored, many-legged tardigrades seemed more closely related to worms than to insects.

If these findings are accurate, Blaxter told Mental Floss in an email, they challenge the very structure of the Panarthropoda family tree, which assumes "the leggy moulting animals are more closely related to each other than they are to wormy things like nematodes."

But he notes that there's lots more research to be done before issuing that challenge: "We have only looked at a tiny fraction of the 10 or more million species on Earth. Every new group, and possibly every species, will have something exciting in it we haven't seen before, and didn't imagine."

9 Tiny Facts About the Chevrotain

Dave Curtis, Flickr // CC BY-NC-ND 2.0
Dave Curtis, Flickr // CC BY-NC-ND 2.0

With a round body, spindly legs, and long fangs, this odd creature gives the platypus a run for its money. Also known as the mouse deer, chevrotains are shy and mysterious, and not much is known about them. But here's what we do know.

1. Chevrotains are not mice, nor are they deer.

Lesser mouse deer or chevrotain
BirdHunter591/iStock via Getty Images

At first glance, these animals look like a weird mash-up of a deer, a mouse, and a pig. Mouse deer share a suborder with deer (Ruminantia) but are not considered “true deer.” They have their own family, Tragulidae.

2. Chevrotain species vary by weight.

Mouse deer in Thailand
MonthiraYodtiwong/iStock via Getty Images

These creatures are way smaller than any deer. Depending on the species, a chevrotain can weigh anywhere from 4 to 33 pounds. The smallest species is the lesser Malay, while the largest is the water chevrotain. No species gets any larger than a small dog.

3. There are a lot of different kinds of chevrotains.

Mouse deer
aee_werawan/iStock via Getty Images

This tiny animal comes in many variations. The family has been classified into two genera: true chevrotains (Hyemoschus) and the mouse deer (Tragulus). The spotted mouse deer are still very mysterious, so scientists have placed them in their own genus called Moschiola. Despite being categorized in different genera, they all share a similar look.

4. Chevrotain fangs are fiercer than Dracula's.

Chevrotain in a woodland
BirdHunter591/iStock via Getty Images

Open up a chevrotain’s mouth and you’ll find two long fangs. They're especially elongated in males, which use the needle-like canines to stab each other. Thanks to an extra thick coat and robust muscles around the neck and rump, these adorable fighters are protected from bites during combat.

5. Some consider the chevrotain a living fossil.

Chevrotain sticking its tongue out
Josh More, Flickr // CC BY-NC-ND 2.0

Chevrotains are the most primitive of ruminants. Like deer and similar hoofed animals, they have even-toed hooves and a multi-chambered stomach. But unlike deer, chevrotains have a three-chambered stomach instead of four, and they lack horns or antlers. They haven't changed or evolved much during their time on Earth. Scientists see them as an evolutionary link between ruminants and non-ruminants.

6. Taking a dip is the water chevrotain's best defense.

The water chevrotain is known for its ability to dive underwater when it senses a predator nearby. The miniature swimmers scrunch up and walk on the bottom of rivers and streams to prevent being picked up by the current. If there are any reeds or plants around, the animals will grab them to stay tethered. Chevrotains are able to hold their breath for about four minutes.

While hiding from hungry predators, the water chevrotain can reemerge to get some air before diving back down. Still, the animal tires easily, and can only swim for short periods of time.

7. Childbirth is an expedited experience for chevrotains.

Chevrotain in a woodland
aee_werawan/iStock via Getty Images

After getting pregnant, a female chevrotain will carry the offspring for five to nine months, depending on the species. The baby can usually stand on its own within one hour of being born. Mothers will visit their young periodically for feedings and stand on three legs while nursing.

Chevrotains are known for their ability to be almost continuously pregnant—greater and lesser Malay mouse deer can mate again only a few hours after giving birth.

8. Chevrotains are shy wallflowers.

Chevrotain in a woodland
cowboy5437/iStock via Getty Images

Due to their small size, chevrotains are preyed upon by many different animals. Lacking antlers or horns for protection, the tiny animals are forced to lead secluded lives. Some species are nocturnal and very rarely seen. Chevrotains are very shy and often graze alone, only coming together to mate. They communicate with a series of smells and noises; this timid behavior makes it difficult for scientists to study them.

9. Chevrotain hooves make a lot of noise.

Chevrotain in a woodland
asxsoonxas/iStock via Getty Images

Although normally peaceful, a male will angrily beat his hooves when agitated—they can stomp around four to seven times a second. This “drum roll” technique wards off predators and warns other chevrotains in the area that there’s danger.

Additional sources: "Water Chevrotain," Amazing Animals of the World; "Chevrotains (Tragulidae)," Grzimek's Animal Life Encyclopedia; Mammals IV, Gale Virtual Reference Library

'Lost Species' of Tiny, Rabbit-Sized Deer Photographed in Vietnam for the First Time in 30 Years

Global Wildlife Conservation
Global Wildlife Conservation

The silver-backed chevrotain, also called the Vietnamese mouse-deer, is elusive. It's so elusive that scientists had feared it was extinct after none had been photographed for decades. But as The Washington Post reports, the first images taken of the mammal in nearly 30 years prove that the species is still alive in the woods of Vietnam.

No larger than small dogs, chevrotains are the tiniest ungulates, or hoofed animals, on Earth. They have vampire-like fangs and skinny legs that support their bodies. Silver-backed chevrotains are characterized by the silver sheen of their tawny coat.

The tiny population native to Vietnam has been devastated by poachers in recent decades. That, and the animal's natural shyness, make it incredibly difficult to study. Before this most recent sighting, the last time scientists had recorded one was in 1990.

Global Wildlife Conservation, the Southern Institute of Ecology, and the Leibniz Institute for Zoo and Wildlife Research teamed up in hopes of documenting the lost species. Researchers interviewed residents and government forest rangers in the Vietnamese city of Nha Trang about the silver-backed chevrotain, looking for tips on where to find one. Residents said that while populations had been hit hard by hunting, the animals were still around.

Based on this local ecological knowledge, scientists set up three camera traps in the Vietnamese woods. In just five months, they captured 275 photographs of the little mouse-deer. They then installed 29 additional cameras and snapped 1881 new images in that same length of time.

“For so long this species has seemingly only existed as part of our imagination," Global Wildlife Conservation associate conservation scientist An Nguyen said in a statement. "Discovering that it is, indeed, still out there, is the first step in ensuring we don’t lose it again, and we’re moving quickly now to figure out how best to protect it.”

Now that a silver-backed chevrotain population has been located, researchers plan to conduct the first-ever comprehensive survey of the species. Once the data is collected, it will be used to build a plan for the species' survival.

[h/t The Washington Post]

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