Male mosquitoes were once bloodsuckers – 12/07/2023 – Science

Every mosquito that has ever bitten you was a female — for them, blood is the perfect dinner. Only females have mouthparts capable of piercing the skin. But insects found trapped in amber, described in a study published last Monday (4) in the journal Current Biology, suggest that one day males may also have fed on blood.

When small animals or plants become trapped in sticky tree resin, they can be preserved if the resin solidifies and forms amber. “In Lebanon, I found about 450 different outcrops of amber, which is a lot for a small country,” said Dany Azar, a paleontologist at the Nanjing Institute of Geology and Paleontology (China) and the Lebanese University and one of the authors of the paper. .

Lebanese amber is rich in preserved fossils, called inclusions, and dates back to about 125 million years ago, in the early Cretaceous. In addition to being the Age of Dinosaurs, it was also a time when flowering plants were becoming more common.

Azar says he studies the inclusions to understand how flowering plants and pollinating insects evolved together.

The paleontologist collected the amber samples used in the study about 15 years ago in central Lebanon, but thought they belonged to a group of insects he wasn’t focused on, so Azar didn’t prioritize them for study. But as he polished one of the samples to obtain a thin slice that could be examined under a microscope, he was surprised.

“To my great surprise, I said, ‘Oh, my God, that’s a mosquito,'” Azar said.

His co-author and former doctoral advisor, André Nel, of the National Museum of Natural History in Paris, confirmed that two specimens appeared to be the oldest known fossils of the mosquito family, with sharp, elongated mouth parts covered in small bristles similar to teeth. A closer look at the insects revealed another surprise.

“I said, ‘André, I didn’t drink anything, but I’m seeing something bizarre here, these are males,'” Azar recalls.

The insects had pincer-shaped organs called claspers on their abdomens, which are used to hold females during mating. The presence of these claspers meant that Azar and Nel had encountered something that seemed impossible: male mosquitoes with mouth parts designed to suck blood.

Modern male mosquitoes feed on nectar and plant juices — most of the time, females do too, they only drink blood when they need extra protein to produce their eggs. Scientists have long believed that mosquitoes and their biting fly relatives evolved from plant-eating ancestors and that females later evolved to have the ability to drink blood.

“Now we think that, originally, the mosquito could have been hematophagous,” said Azar. “With the emergence of flowering plants, this function could have been forgotten later during the evolution of these insects.”

The idea that these ancient male mosquitoes fed on blood was “interesting, fascinating and controversial,” said Dale Greenwalt, a paleobiologist at the National Museum of Natural History in Washington.

After all, feeding on blood is a riskier strategy than sipping nectar, as it carries the threat of being crushed — one of the reasons why modern female mosquitoes only feed on blood when they need it for reproduction. It is also possible that the insects in the study were not exactly mosquitoes, or that perhaps their bristle mouthparts, although different from those of modern males, were not used for drinking blood.

Greenwalt said that with their hypothesis, Azar and Nel “have ventured into very delicate terrain” but that their bold thesis could boost scientific research.

“Some scientists are very conservative, others are not,” Greenwalt said. “The good thing about this is that if those who are not conservative turn out to be wrong, those who are conservative will correct the mistake later. And we will have to wait and see.”