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Here's why cockroaches are indestructible

Genome sequencing reveals the secrets of this nasty insect
by Maggie Fox /  / Updated 
Image: A close-up image of the American cockroach
A close-up image of the American cockroachSheng Li / Nature Communications

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They can regrow lost legs. They make their own antibiotics. And they have an almost supernatural sense of smell.

Now Chinese researchers have sequenced the genome of the American cockroach and discovered why they are so hard to kill.

It’s all in the DNA, they report in the journal Nature Communications.

The American cockroach, known scientifically as Periplanta Americana, has an enormous genome, Shuai Zhan and colleagues at the Chinese Academy of Sciences in Shanghai, found.

And it’s more closely related to termites than it is to German cockroaches, despite their shared unsanitary habits and ability to horrify homeowners and terrorize tenants.

Cockroaches spread germs and can aggravate asthma and allergies.

"The harm of American cockroaches is becoming more serious with the threat of global warming," Zhan's team wrote. “Our study may shed light on both controlling and making use of this insect.”

And the DNA explains why they are so prolific.

When under stress, females can lay unfertilized eggs that will hatch in a process called parthenogenesis or “virgin” reproduction. The team found genes that explain how this can happen.

Cockroaches can regenerate limbs

They can also survive terrible injuries.

“The American cockroach has a strong capability of limb regeneration during the nymph stages, which is the main reason to call it ‘Xiao Qiang’ in China,” the researchers wrote. The name translates as “little mighty one," and the team found genetic pathways that underlie the process.

Image: A close-up image of the American cockroach
A close-up image of the American cockroachSheng Li / Nature Communications

DNA can also explain their noxious habits.

“Cockroaches generally live in moist and unsanitary areas and are particularly fond of fermenting foods; thus, they have numerous opportunities to be exposed to microbes and pathogens,” the team wrote. The insects have extra genes related to chemoreception, or smell.

And the insects have evolved sophisticated ways to deal with their dirty environments. Their cells respond to infection with bacteria and fungi by secreting antimicrobial peptides that go into the hemolymph — the juice that squirts out when you stomp on a roach.

Plus they have natural detoxification mechanisms. Targeting these genetic pathways might be a better way to kill the pests, the Shanghai researchers suggested.

It also might be possible to exploit these properties, they said.

“Beyond serving as a pest, this cockroach is also important in traditional Chinese medicine, well documented in Chinese medical encyclopedias,” they wrote. “Moreover, its ethanol extract has been developed as a prescribed drug (Kang Fu Xin Ye) for wound healing and tissue repair.”

Understanding the genetic secrets could help scientists replicate the cockroach’s superpowers, they said.

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