I remember moving to Austin in the early 1980s. A position at the University of Texas at Austin beckoned, and the first task was to find an apartment within biking distance of the university. We settled on a garage apartment and unknowingly moved in with Periplaneta americana — hundreds of American cockroaches! And these are the big ones (up to 2 inches long) that can fly. We eventually gained the upper hand, but it was a challenge to get rid of our roommates.
Cockroaches have existed on Earth for 300 million years, which means they lived with the dinosaurs. A study of the insect’s genome has given us clues as to how this creature has been so successful for millennia. A genome is the complete set of all the DNA in an animal’s cells, made up of bases written as A, C, G and T. Chinese researchers have sequenced the genome of the American cockroach and compared it to the Australian and German cockroach genomes.
There are a few surprises revealed in the analysis. The American cockroach has a huge genome: 3.38 billion bases. At this size, it makes it the second largest among insects, with only locusts being larger. This also makes it slightly larger than the human genome, which can be estimated at a little over 3.2 billion bases. While its genome is closely related to the German and Australian cockroaches, it has been found to be more similar to two species of termites. Hmmm ... these are both species you do not want to see in your house! While the American cockroach prefers living in and around human homes, it is also found in dark, moist environments like these termite species.
Included in the super-sized genomes of cockroaches are a large grouping of genes that help explain their evolutionary staying power. After the atomic bombs fell on Hiroshima and Nagasaki, Japan, observations indicated that the only living organisms at Ground Zero were cockroaches. These insects have great adaptive ability.
The genome contains many genes involved in chemoreception, which allows them to smell and taste many potential food sources in the environment. These creatures are omnivores, meaning that they eat both plant and animal materials, and they seem to survive on anything. In our Austin apartment, I am sure they could live on just the grease marks in old pizza boxes.
American cockroaches have also accumulated a variety of genes that allow them to detoxify substances. This helps with chemicals they encounter, including the ones we use to keep them out of our kitchens.
Cockroach genomes also contain genes that help them regulate their growth. They can grow fast when food is plentiful and grow more slowly when food is scarce. Also revealed are genes that allow them to re-grow limbs. Imagine when the day comes that we can understand these genes and can begin to apply this to help humans who have lost limbs — this would be a breakthrough brought to us by the creepy crawlies under our sinks!