Bed bugs swept the Earth alongside dinosaurs 100 million years ago | Science



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Although today's humans run little risk of being crushed by a T. rex, they are still vulnerable to the bites of a different prehistoric pest: bed bugs.

A new study by an international team of researchers reveals that bed bugs evolved about 100 million years ago, when dinosaurs still dominated the Earth, making them twice as old as entomologists thought before. Early hypotheses suggested that bats were the first hosts of the parasitic insect, but fossil records and DNA evidence show that creatures actually appeared tens of millions of years ago previously, according to the study published this week in Current biology.

"The first hosts we can follow are bats," says Klaus Reinhardt, lead author and bedbug researcher at the Dresden University of Technology in Germany. "But the oldest [bat] fossil is [from] about 50 or 60 million years ago. … It is impossible for bats to be the first group of bed bugs, because they existed before proto-bats flew through the air.

Researchers used genetic material from 34 bed bug species collected over the past 15 years to trace the evolutionary tree of the insect. Some of the samples were provided by natural history museums or other scientists in the field, but others required a little more work. Reinhardt says the authors are flying around the world, from Africa, South America and Southeast Asia, in hopes of finding as many genres as possible . After spending a lot of time in bat guano, wading to the knees, team members collected specimens from five bedbug sub-families in order to develop a evolutionary history updated parasitic parasites.

Pushpin and bat

Bed bugs are older than bats, a mammal that previously thought to be their first host 50 to 60 million years ago. Bed bugs had actually evolved about 50 million years ago.

(Mark Chappell / University of California, Riverside)

From these collected specimens, the researchers extracted DNA samples and, focusing on five particular points of the genome, compared their results across genera in order to understand the link that united the genealogical tree of the genome. Bedbugs. Assuming the genes change at a constant rate, they could then work backwards to establish a chronology of bed bug evolution.

This earlier date is also corroborated by two ancient fossils – one of the precursors of bed bugs and related species, and the other of an old bug – both of which would have the appearance of bed bugs about 100 years ago. millions of years, says Reinhardt. If so, bed bugs first appeared in the Cretaceous, meaning that the critters rushed next to pterodactyls and triceratops with large horns.

Although people can imagine the big T. Rex groaning about its itching, Reinhardt says the unlikely dinosaurs would serve as bedbugs. Pests prefer to feed on animals that settle in comfortable groups and dinosaurs tend to move more freely. Some small mammals of the time are more likely to be candidates, but Reinhardt says it takes even more work to find out which creatures were the first to suffer the small anger of the bedbug.

According to Tom Henry, Curator of Entomology at the Smithsonian National Museum of Natural History, the authors' work raises many questions that future researchers will have to answer. Although bats may have evolved earlier and we simply do not have fossil evidence, the study encourages entomologists to rethink their understanding of the original host of bed bugs.

"Their phylogenetic reconstruction, using the known fossil record, provides compelling evidence that bed bugs have evolved before bats," Henry states in an e-mail. "In this case, they necessarily fed on other ancestral mammals, perhaps a forerunner of bats, who also lived in caves or other protected areas."

The study also challenges previously accepted ideas about how parasite eating habits have evolved. According to previous hypotheses, bed bugs became increasingly selective over time, moving from generalists who fed on everything that happened to them to specialists who turned to specific hosts as sources of food. This trend has been observed in other species; those who focus their efforts on a specialized diet can become very effective at acquiring nutrients from selected sources and sometimes outperform their less difficult counterparts.

However, researchers' findings do not support a global shift in eating habits from generalists to specialists, says Reinhardt. In fact, in a number of cases, parasites seem to have expanded their diet.

The three documented times that have evolved to feed on human beings, for example, seem to support the idea that bed bugs can become generalists. Instead of switching from their previous specialty diets, bed bugs simply added humans to the menu when the opportunity arose, Reinhardt said. The authors do not know what might prompt a change in this direction, other than the vague notion that bedbugs could take advantage of ecological opportunities.

"Let's say you're a bat specialist and you live in a cave. Suddenly, this human really nice, smelly and juicy comes all the time. It would be an ecological opportunity for a new source of food, "says Reinhardt. "If, as a species, you still have the ability to suck those bats, but you also have the ability to suck humans now, then by definition you would be a kind of generalist."

Nevertheless, understanding the proposed evolution of the specialist to the generalist is far from complete, says Reinhardt. And the ecological opportunity does not materialize in every case, because the authors found that when they tried to offer their own bodies as sustenance for some of their living specimens, the insects turned their noses, refusing to feed themselves .

The staggered timeline of bedbugs also conflicts with the theories of the evolution of two varieties of pests that commonly affect humans today: the tropical bedbug and the bedbug. While other researchers believed that the evolutionary gap was due to the fact that insects grew by feeding on distinct species of ancient and modern humans …Homo erectus and Homo sapiensThe authors of the study estimate that bedbugs have separated more than 30 million years before their human hosts roam the Earth.

The results of the authors could influence our understanding of the evolution, not only of bed bugs, but also of other species of parasites, explains Henry.

Reinhardt admits that he was a little "unsatisfactory" that the results of the study question many previous hypotheses without finding any positive answers to replace them, but he hopes the unresolved issues will lead to further research.

"You have to rewrite some of the ideas in the manual about why there are pairs of human-parasite species," says Reinhardt. "You have to rewrite a bit of what the original host is."

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