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."

11 Cute Facts About Crickets

iStock.com/sirichai_raksue
iStock.com/sirichai_raksue

They’re insects that invade our homes, but they’re beloved around the world. They’re living thermometers with ears on their knees, and they just might save the world. Here are 11 surprising (and often adorable) facts about crickets.

1. Crickets were named for the sounds they make.

The word cricket comes from the Old French word criquet, and refers to the cricket’s song—people once thought that those repeated chirps sounded like “criquet … criquet … criquet.”

Interestingly, the name for the sport of cricket has a totally different origin: it comes from an Old French word for goal post.

2. They don't make sound the way you think they do.

How do crickets chirp? Old-timey illustrators sidestepped this question by drawing them playing tiny violins. There’s a persistent myth that crickets rub their legs together to make sound. In fact, they sing with their wings.

Run your finger down the teeth of a comb and you’ll hear an almost musical rattle. Crickets make sound in a similar way. They rub a scraping organ on one wing against a comb-like organ on the other.

Each cricket species has distinctive noise-making structures that produce unique sounds. Scientists have even managed to recreate the sound of an extinct cricket relative, a fossilized Jurassic bush cricket (katydid), by examining the shape of its wings.

3. Most female crickets don't sing.

That cricket in your house that’s endlessly chirping away? It’s probably a male. Most female crickets lack those sound-making wing structures. There are exceptions: Some female mole crickets (relatives of “true” crickets) sing. And males of some cricket species never make a peep.

So why do male crickets (usually) chirp?

4. Crickets sing out of love—and anger.

It’s all about securing a mate. But crickets don’t just sing a pretty song and wait for the admirers to trickle in. Many of them have a whole repertoire of calls: There’s one for attracting females from afar, another for close-up courtship, and even a triumphal after-mating song. Crickets also sing to intimidate rival males, and some of a male’s more romantic tunes may trigger nearby females to fight each other.

5. You can use cricket songs as a thermometer.

Crickets call more frequently when the weather gets hotter. It’s such a proven phenomenon that you can use it to calculate the temperature. The snowy tree cricket’s gentle calls seem to match the heat especially accurately. The Old Farmer’s Almanac recommends that you count the number of chirps in 14 seconds and add 40 to get the temperature in Fahrenheit.

6. Some crickets have evolved to stay silent.

A particular fly species has invaded the island of Kauai in Hawaii, and it’s the stuff of cricket nightmares: It uses its incredibly sophisticated hearing system to find a singing cricket and drop maggots on it. Those maggots burrow into their victim and devour it from the inside.

Male crickets on Kauai have responded in a remarkable way. They’ve evolved wings more like a female cricket’s, which means they’ve lost the ability to chirp. Those silent, safe crickets compensate for their lack of courtship songs by spending more time on the move [PDF], which improves their chances of running into potential mates.

7. Crickets listen with their legs.

Insects have ears in weird places. Those cricket-eating parasitic flies, for example, have ears just below their head and neck. When a butterfly lands and folds up its wings, it’s exposing its ears. And cricket ears are tiny spots, just a fraction of a millimeter long, on their front legs just below the knees. They’re some of the smallest ears of any animal, but they’re highly sensitive.

8. There's a whole rainbow of crickets.

If you’ve found a cricket in your house or yard, chances are that it’s black or brownish. But that somber insect has some pretty colorful relatives. There’s the red-headed bush cricket, also known as the handsome trig—and it’s, well, pretty handsome for a cricket. The snowy tree cricket is pastel green with wings shaped like tennis rackets. And if you visit the tropics, where there are more cricket species than anywhere else, you might spot this intricately patterned Nisitrus species.

That’s just the so-called “true” crickets, members of the family Gryllidae. People also use the word cricket for many close Gryllidae relatives, and they’re an amazing bunch of insects ...

9. Crickets have rock star relatives.

One group of cricket relatives is the mole crickets. These insects have big claws and live underground. To attract mates, they throw little rock concerts: They dig horn-shaped burrows, turning their homes into amplifiers that make their calls extra loud.

Then there are the bush crickets, or katydids, which come in hot pink and other startling hues. And some katydids look so much like leaves, complete with dried patches, chew marks, and holes, that you’ve probably walked right past them without realizing you’re being watched.

Another group of cricket relatives, New Zealand’s wetas, includes enormous insects that can outweigh a mouse. The name weta comes from a Maori word for “god of ugly things.” Weta Workshop, the company that created props, costumes, and creatures for the Lord of the Rings films, took its name from these otherworldly insects.

9. People love crickets.

Insects often get a bad rap, but people of many cultures adore crickets. Chinese people have long kept these insects as good luck charms—and for cricket-on-cricket battles. Crickets are beloved in Japan, especially for their musical songs. In Brazil, some species are considered to be signs of hope or incoming wealth (though others are thought to be omens of illness and death). Charles Dickens wrote a tale called The Cricket on the Hearth that featured a cricket acting as a household’s guardian angel. And who could forget Disney’s Jiminy Cricket, and Cri-Kee from Mulan? Few other insects have received the cute Disney treatment.

10. Crickets live in our homes.

Many types of crickets will happily live in and around houses. House crickets, which are brownish and probably native to Asia, breed inside homes in many cities around the world. Black-colored field crickets will accidentally wander into buildings. And one cricket relative, the greenhouse camel cricket, has been quietly invading residences in the eastern U.S.

Fortunately, these household crickets are mostly harmless. Their poop may stain the curtains, and in rare cases they’ll nibble clothing—but usually the worst they’ll do is annoy you with their incessant calls.

11. Crickets just might save the world.

Imagine a high-protein food that’s packed with vitamins. It’s more efficient to produce than conventional meats, and it generates way less greenhouse gas. This superfood? Yup, it’s crickets. You can now purchase these insects in a variety of forms that are mercifully free of twitching legs—including flour. If westerners can overcome their squeamishness about eating insects, then crickets just may be the future of food.

This story originally ran in 2016.

Elephants Are Evolving Without Tusks Thanks to Poaching

iStock.com/LeighGregg
iStock.com/LeighGregg

Natural selection can take millions of years to shape a gene pool, but in parts of Africa, the extreme pressures of poaching may have changed elephants in just a few decades. As National Geographic reports, more tuskless elephants have emerged in regions where their ivory has made them a target.

Elephant poaching has long been in a problem Africa, but the crisis reached a fever pitch during Mozambique's 15-year civil war. Between 1977 and 1992, 90 percent of the elephants living in the country's Gorongosa National Park were slaughtered for ivory used to fund the conflict.

The diminished numbers aren't the only thing that looks different about Gorongosa's elephants today. Poachers often kill male elephants first because they have bigger tusks, and once they're eliminated, the hunters will go after females. Typically, about 2 to 4 percent of all female African elephants never develop tusks—but among female elephants that survived Mozambique's civil war, that number is 51 percent. The effects of poaching can also be observed in the next generation. Roughly 32 percent of female elephants born after 1992 are tuskless.

The trend can be seen in other parts of Africa where poaching has ravaged elephant populations. In Ruaha National Park in Tanzania, elephant behavior researcher Josephine Smit has observed that over one fifth of female elephants older than 5 years lack tusks. Tusklessness rates reach about 35 percent in females over 25.

The statistics are even harder to ignore in South Africa's Addo Elephant National Park, where tuskless animals made up 98 percent of all female elephants in the early 2000s. South Luangwa National Park in Zambia, Lupande Game Management Area in Zambia, and Queen Elizabeth National Park in Uganda each reported higher-than-average rates of tusklessness immediately following the ivory wars of the 1970s and '80s.

Though poaching is on the decline thanks to bans on the ivory trade and other conservation efforts in Africa, its impact can still be felt. In East Africa, the elephant population was nearly halved between 2008 and 2018. The establishment of wildlife preserves, DNA tracing, and GPS tracking are just a few of the ways conservationists are working to crack down on poachers and restore the species.

[h/t National Geographic]

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