Amber fossils suggest that male mosquitoes were once leeches
Every mosquito that has ever bitten you has been female. For them, a blood meal is the ultimate girls’ dinner. Only females have mouthparts that can pierce the skin. But insects trapped in amber, described in a study published Monday in the journal Current Biologysuggest that male mosquitoes once drank blood too.
When small animals or plants become stuck in sticky tree resin, they can be preserved if the resin hardens into amber. “In Lebanon I found about 450 different pieces of amber, which is a lot for a small country,” said Dany Azar, a paleontologist at the Nanjing Institute of Geology and Paleontology and the Lebanese University, and author of the paper.
Lebanese amber is rich in preserved fossils called inclusions and dates back about 125 million years to the Early Cretaceous. Besides being the age of the dinosaurs, it was also a time when flowering plants became increasingly widespread. Dr. Azar says he studies inclusions with the goal of understanding how flowering plants and pollinating insects evolved together.
He collected the amber specimens in this study about 15 years ago in central Lebanon, but he thought they belonged to a group of insects he wasn’t focusing on, so Dr. Azar they are not a priority for research. But as he polished one of the specimens into a thin slice that could be examined under a microscope, he was surprised.
“Much to my surprise, I said, ‘Oh God, this is a mosquito,'” said Dr. Azar.
His co-author and former doctoral advisor, André Nel, of the National Museum of Natural History in Paris, confirmed that two of Dr. Azar appeared to be the oldest known fossils of the mosquito family, with sharp, elongated mouthparts covered. in small tooth-like bristles. Further examination of the insects yielded another surprise.
“I said, ‘André, I haven’t had anything to drink, but I see something bizarre here: these are men,'” said Dr. Azar.
The insects had pincer-like organs on their abdomens, which are used to hold females during mating. The presence of these grabbers meant that Dr. Azar and Dr. Nel had encountered an apparent impossibility: male mosquitoes with mouthparts designed to suck blood.
Modern male mosquitoes feed on nectar and plant juices. (Usually, females do that too: they drink blood only when they need extra protein to produce their eggs.) Scientists have long thought that mosquitoes and their biting fly cousins evolved from herbivorous ancestors, and that females evolved later. have the ability to drink blood.
“We now think the mosquito might have originally been blood-sucking,” said Dr. Azar. “With the appearance of the flowering plant, this function could simply be forgotten later in the evolution of these insects.”
The idea that these ancient male mosquitoes fed on blood was “interesting, fascinating and controversial,” says Dale Greenwalt, a paleobiologist at the Smithsonian National Museum of Natural History.
After all, feeding on blood is a riskier strategy than sipping nectar because it carries the threat of being bludgeoned to death – a reason why modern female mosquitoes only feed on blood when they need it for reproduction. It’s also possible that the insects in this study turned out to be something different from mosquitoes, or that their bristly mouthparts, while different from those of modern males, might not have been used for drinking blood.
Dr. Greenwalt said that Dr. Azar and Dr. Nel have “stepped on very thin ice” with their hypothesis, but that their bold claim could ultimately advance scientific research.
“Some scientists are very conservative. Some scientists are not,” said Dr. Greenwalt. “The good thing about that is that if those who aren’t turn out to be wrong, those who are will eventually correct the mistake. And we’ll just have to wait and see.”