Just mentioning the word cockroach gives many of us the creeps, right? And it is that its association with bacteria, dirt and garbage in general, makes us feel apprehensive and rejection towards these insects that, curiously, belong to the same order as termites (and that do not cause us such a sensation).
One of the qualities that we know most about termites is their ability to survive. They adapt easily to any environment and, of course, they reproduce quickly. How is it possible that these creepy critters are natural survivors? The sequencing of the genome of the American cockroach revealed very interesting data in this regard.
According to the study, published in the journal Nature Communications, the cockroach ( Periplaneta americana ) has greatly expanded the families of genes related to taste and smell, detoxification and immunity, compared to other insects, key factors of its survival.
Many of the gene families that expanded in the American cockroach also expanded in the German cockroach, which makes sense because both species are made up of omnivorous scavengers that can thrive on rotten food in severely unhealthy environments.
Home: sewers
The American cockroach is a common dweller of sewers. It originally comes from Africa, but was introduced to the Americas in the 17th century. Unlike the German cockroach, which is a major pest found almost exclusively in human dwellings, the American cockroach mainly ventures into basements or lower levels of buildings.
However, both cockroaches are very hardy, and their genes hold the clues as to why. In the study, researcher Sheng Li of South China Normal University and his team found that American cockroaches have the second largest genome of any sequenced insect, just behind the migratory locust ( Locusta migratoria ), albeit 60% of the cockroach genome is made up of repeating segments. The gene families related to taste and smell were much larger than those of other insects, and the researchers found 522 taste receptors in the cockroach . German cockroaches are equally well equipped with 545 taste receptors.
“They need very elaborate systems of smells and flavors to avoid eating toxic things,” explain the researchers.
There are 5,000 described species of cockroaches
American cockroaches also had a larger-than-average set of genes dedicated to metabolizing harmful substances, including some of the ingredients in insecticides. German cockroaches have similar adaptations; Both species developed these genetic changes long before humans entered the scene, the authors clarify.
Thanks to their tendency to live among toxin-producing bacteria and to eat plant matter that could contain toxic substances, cockroaches were “pre-adapted” to the insecticides that humans later throw at them.
The cockroach also possesses an extended family of immunity genes, probably another adaptation to survive unsanitary environments and fermented food sources, as well as a large number of genes dedicated to development, such as the genes responsible for synthesizing the juvenile hormone of the insect or the proteins in your exoskeleton.
A greater understanding of the cockroach genome may help researchers find new ways to control pest species, the researchers wrote.
Referencia: The genomic and functional landscapes of developmental plasticity in the American cockroach. Sheng Li, Shiming Zhu, Qiangqiang Jia, Dongwei Yuan, Chonghua Ren, Kang Li, Suning Liu, Yingying Cui, Haigang Zhao, Yanghui Cao, Gangqi Fang, Daqi Li , Xiaoming Zhao, Jianzhen Zhang, Qiaoyun Yue, Yongliang Fan, Xiaoqiang Yu, Qili Feng & Shuai Zhan. Nature Communications volume 9, Article number: 1008 (2018) DOI: https://doi.org/10.1038/s41467-018- 03281-1
