American cockroaches thrive in cities, thanks to their incredibly long genomes

Few insects have a reputation for grossing people out as thoroughly as the American cockroach. The so-called water bugs, which thrive indoors on fermenting and rotting foods, are rich sources of disease-causing bacteria. Now, researchers have sequenced their genome for the first time—and have uncovered some of the secrets to their uncanny ability to survive in our urban jungles.

Compared with other insects, the genome of the American cockroach (Periplaneta americana) is the second largest sequenced to date after the locust. Like the locust, much of the cockroach genome, some 60%, is made of repetitive elements—sequences of DNA that occur over and over. And compared with three other species in its family—the German cockroach and two termite species—it is actually more closely related to the termites.

But the secret to its urban success may lie in another part of the genome. The American cockroach has genes that code for more than 150 scent receptors and 500 taste receptors, the most found in any insect so far. These, coupled with hundreds of other chemical receptors, are likely the reason cockroaches are such effective scavengers, the researchers report today in Nature Communications.

The researchers also found that cockroaches have genes that allow them to regrow broken limbs—the same genes present in other insects, including the fruit fly. The team proposes that future research will better clarify the evolutionary relationship between cockroaches and termites, and may provide helpful information for controlling both pests.