Cockroach DNA Shows Why They're Basically Indestructible

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Most people are all too aware that cockroaches are horrifyingly resilient beings. Yes, they can and have survived nuclear blasts, and surely stand to inherit the Earth after we all succumb to the apocalypse. Why is this creature able to thrive in the face of pesticides, the loss of limbs, disgusting conditions, a range of climates, and even nuclear fallout, in urban kitchens across the world? As Inside Science reports, a new study on the genome of the American cockroach shows that certain genes are key to its wild evolutionary success.

In an article published in Nature Communications, researchers from South China Normal University in Guangzhou, China report that they sequenced and analyzed the genome of Periplaneta americana, and in the process they discovered just how indestructible this scourge is. They found that the cockroach (native to Africa, despite its American moniker) has more DNA than any other insect whose DNA has been sequenced except the migratory locust. The size of its genome—3.3 billion base pairs—is comparable to that of humans.

They have a huge number of gene families (several times the number other insects have) related to sensory reception, with 154 smell receptors and 522 taste receptors, including 329 taste receptors specifically related to bitter tastes. These extra smell and taste receptors may help cockroaches avoid toxic food (say, your household pesticide) and give them the ability to adapt to a multitude of different diets in different environments.

They also have killer immune systems able to withstand pathogens they might pick up from the rotting food they eat and the filth they like to live in. They have many more genes related to immunity compared to other insects.

The genome analysis might give us more than just a newfound respect for this revolting pest. The researchers hope to find a way to harness this new knowledge of cockroach immunity to control vermin populations—and create an eradication method slightly more effective than just stomping on them.

[h/t Inside Science]

This 'Time-Traveling Illusion' Is Designed to Trick Your Brain

A team of researchers from the California Institute of Technology (Caltech) have designed an illusion that might trick your brain into seeing things that aren’t there, the New Atlas reports.

Dubbed the Illusory Rabbit, it provides instructions that are simple enough to follow. Start playing the YouTube video below and look at the cross in the middle of the screen while also watching for flashes that appear at the bottom of the screen. Most importantly, you’ll want to add up the number of flashes you see throughout the video. (And make sure your volume is up.)

We don’t want to spoil the fun, so before we explain the science of how it works, check out the video and try it for yourself.

Did you see three flashes paired with three beeps? You’re not alone. This is due to a phenomenon called postdiction, which is a little like the opposite of prediction. According to a paper outlining these findings in the journal PLOS ONE, postdiction occurs when the brain processes information retroactively [PDF]. This occurs in such a way that our perception of earlier events is altered by stimuli that come later. In this case, you might think you missed the flash paired with the second of the three beeps, so your mind goes back and tries to make sense of the missing information. That's why you may see an “illusory flash” in the middle of the screen, sandwiched between the two real flashes.

For this reason, the researchers call the mind trick a “time-traveling illusion across multiple senses” (in this case, vision and hearing). It’s successful because the beeps and flashes occur so rapidly—in less than one-fifth of a second. The senses essentially get confused, and the brain tries to fill in the gaps retroactively.

"Illusions are a really interesting window into the brain," the paper’s first author, Noelle Stiles, said in a statement. "By investigating illusions, we can study the brain's decision-making process.” Researchers wanted to find out how the brain “determines reality” when a couple of your senses (in this case, sight and hearing) are bombarded with noisy and conflicting information. When the brain isn’t sure of what’s going on, it essentially makes up information.

“The brain uses assumptions about the environment to solve this problem,” Stiles said. “When these assumptions happen to be wrong, illusions can occur as the brain tries to make the best sense of a confusing situation. We can use these illusions to unveil the underlying inferences that the brain makes."

[h/t New Atlas]

How Did 6 Feet Become the Standard Grave Depth?

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It all started with the plague: The origins of “six feet under” come from a 1665 outbreak in England. As the disease swept the country, the mayor of London literally laid down the law about how to deal with the bodies to avoid further infections. Among his specifications—made in “Orders Conceived and Published by the Lord Mayor and Aldermen of the City of London, Concerning the Infection of the Plague”—was that “all the graves shall be at least six feet deep.”

The law eventually fell out of favor both in England and its colonies. Modern American burial laws vary from state to state, though many states simply require a minimum of 18 inches of soil on top of the casket or burial vault (or two feet of soil if the body is not enclosed in anything). Given an 18-inch dirt buffer and the height of the average casket (which appears to be approximately 30 inches), a grave as shallow as four feet would be fine.

A typical modern burial involves a body pumped full of chemical preservatives sealed inside a sturdy metal casket, which is itself sealed inside a steel or cement burial vault. It’s less of a hospitable environment for microbes than the grave used to be. For untypical burials, though—where the body isn’t embalmed, a vault isn’t used, or the casket is wood instead of metal or is foregone entirely—even these less strict burial standards provide a measure of safety and comfort. Without any protection, and subjected to a few years of soil erosion, the bones of the dearly departed could inconveniently and unexpectedly surface or get too close to the living, scaring people and acting as disease vectors. The minimum depth helps keep the dead down where they belong.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This article originally appeared in 2012.

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