Here is the reason why cockroaches can survive just about anything

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The genome of the American cockroach has been sequenced for the first time, revealing why these creepy-crawlies are so tenacious survivors.

The roach (Periplaneta americana) is a widespread gene families related to the taste and the smell, for detoxification and immunity compared to other insects, according to a new study published March 20 in the journal Nature Communications.

“It makes total sense in the context of lifestyle,” says Coby Schal, an entomologist at North Carolina State University, who was part of a team that last month reported an analysis of the genome of the German cockroach (Blattella germanica). Many of the gene families that expanded in the American cockroach have also been extended in the German cockroach, Schal said. This is logical, because both species are omnivorous scavengers that can thrive on rotting food in a seriously unhealthy environments.

Discriminating tasters

The American cockroach is a denizen of the sewer. It is originally from Africa, but was introduced in America in the early 1500’s. Unlike the German cockroach, which is a major pest found almost exclusively in human dwellings, the American cockroach usually ventures only in the basements or lower levels of the buildings, Schal said. [Photos: Insects and Spiders That Can be Your Home]

Both the cockroaches, though, are hardy survivors and their genes are the keys why. In the new study, researcher Sheng Li of South China Normal University and his colleagues that the American cockroaches have the second-largest genome of any insect ever sequenced, right behind the migratory locust (Locusta migratoria), even though a good 60 percent of the roach genome is composed of repeated segments. Gene families related to the taste and smell were much larger than those of other insects, and the researchers found 522 flavor, or taste receptors in the roach. German cockroaches are also well-equipped, Schal said, with 545 taste receptors.

“They have a very extensive taste and smell systems to prevent the eating of poisonous stuff,” Schal said.

Hardy survivors

American cockroaches also had a larger-than-average suite of genes devoted to the metabolize of nasty substances, including some of the ingredients in insecticides. German cockroaches have similar adaptations, Schal said. Both species developed genetic changes long before man came on the scene, he said. Thanks to their tendency to live in the toxin-producing bacteria to eat plant material that might hold toxic substances, roaches were “pre-adapted” to the insecticides that people can throw, Schal said.

The American cockroach also had an extended family of immunity genes, probably another adaptation for the survival of unhealthy environments and the fermentation of food, Li and colleagues wrote. Finally, the roach had a large number of genes devoted to development, such as the genes responsible for the synthesis of the insects, the juvenile hormone or the proteins in the skeleton. This made sense, the researchers wrote, since American cockroaches can grow up to 2 cm (53 inches) long and molt many times to reach that size.

For a better understanding of the cockroach genome can help researchers come up with new ways to control pest species, the researchers wrote. An example, Schal said, the Asian cockroach (Blattella asahinai), a close relative of the nasty German cockroach that lives outdoors and don’t bother humans much. It would be interesting to see if there are differences between the Asian and German cockroach that could explain why the one is dependent on the man-made environments and the other not, Schal said.

“There are 5,000 described species of cockroaches, and now we have two [full] taken,” Schal said. “So we need more.”

Original article on Live Science.

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