There was a time, at least 90 million years ago, when mammals were free of lice. But it did not last long. The ancient ancestor of modern mammals and elephant dogs picked up bird skin parasites and developed a remarkable relationship and perhaps an intimate relationship between mammals and lice that continues even today. That is the conclusion reached by biologist Kevin Johnson at the University of Illinois at Champaign and his fellow authors, following a genomic study of the mammal ‘lice tree’. Studies suggest that most of the lice that make up modern mammals can trace their roots to a single aphid on a single mammal that survived before the extinction of non-bird dinosaurs.
The story of mammals is rarely told, but in some ways it is as fascinating as the story of mammals. For example, when seals became accustomed to living in the oceans tens of millions of years ago, their lice became accustomed to being the only species of sea urchin2. “Lice can change very complexly with a human being,” says Bret Boyd, a biologist at Virginia Commonwealth University in Richmond. But lice also have a remarkable ability to change what they do not know when the opportunity arises. It is this ability that helps explain why lice found in seals, skunks, elephants and humans all seem to come from a single ancestor. After examining the genetic data from 33 species of lice from all major mammal groups, Johnson and his colleagues concluded that lice have evolved into mammals at least 15 times since they began to destroy mammals.
Crawling on diversity
In part, it is because of these changes in the home environment that the lice-infested mammal tree seems to be extremely difficult to integrate – but that is not the only reason. Finding lice from a variety of mammals to extract their DNA is a daunting task, says Vincent Smith, a biodiversity informatics researcher at the Natural History Museum in London.”The tree has been the subject of debate for years,” Boyd said. “Looks like Kevin got that.”However, Jessica Light, an evolutionary specialist at Texas A&M University College College, warns that it may soon be too late. “Future studies with additional samples may or may not support these findings,” he said. Pinching a aphid tree has far-reaching effects. Biologists in the early twentieth century used lice to test their theories for a cohesive, evolutionary evolution of two or more species, says Smith. Do you think that this new study might entice biologists interested in the broader evolutionary process of looking at lice.
The aphid tree may also provide important information on the transformation of the host – a hot topic, given that the origin of some diseases including COVID-19 can be explained by changing the host from other animals to humans. Anything that gives us a deeper understanding of process technology “may shed light on how to reduce the risk of contracting new diseases in humans”, says Johnson.
But the process is complicated. Boyd states that one of the reasons that blood-sucking lice are able to survive on mammals is that germ-carrying insects carry symbiotic bacteria that provide B vitamins that are not readily available in the blood of mammals. However, as lice can change between mammals, it seems that bacteria can switch between lice. While researching sea lice a few years ago, Boyd and his colleagues discovered that its symbolic viruses were recently discovered.”It is possible that the lice lost their ancestor symbiont and replaced it with a new one, so it is like changing the host to a deeper level,” he said. “It’s levels of difficulty.”
Source Journal Reference: Nature News, https://www.nature.com/articles/d41586-022-01833-6
