‘But it’s male’: scientists report earliest known mosquito fossil from a time when both sexes fed on blood
- Scientist with amber fossils from Lebanese forest uses hi-tech equipment in China to identify preserved mosquitoes
- Paper says male of the species may once have fed on blood, as female mosquitoes still do, before evolving to live off plants
While only female mosquitoes feed on blood today, researchers have discovered a new mosquito species – the earliest yet discovered – in which the males may have also fed on blood.
The discovery, made possible with the help of advanced microscope equipment in China, challenges the scientific record for how early mosquito evolution occurred.
The two male fossilised mosquitoes found in Lebanese amber dated to the Early Cretaceous period were reported in a paper published by the international research team on Monday in the Cell Press journal Current Biology.
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Dany Azar, lead author of the paper and a researcher at the Nanjing Institute of Geology and Palaeontology under the Chinese Academy of Sciences and at Lebanese University, discovered samples of amber that formed under a tropical forest in central Lebanon.
After not studying these samples for more than a decade, Azar began looking at the fossils last year, but a lack of reliable equipment meant he could not clearly identify them, said Huang Diying, a researcher at the Nanjing institute and an author of the paper
On Tuesday, Huang said that after Azar joined the Nanjing Institute in February, he was able to use the institute’s advanced equipment to identify the fossils.
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The Chinese-language news site the Science Times said while at the institute Azar used laser confocal and fluorescence microscopes to observe the fossils. With this equipment scientists could “see the fossils very clearly” and identify their features, Huang said.
The male mosquitoes discovered had parts that greatly resemble those of modern females – “piercing mouthparts” with sharp mandibles that allow the insect to pierce the skin and suck up blood.
Mosquitoes feed on fruit juice and nectar, and in the modern day only female mosquitoes are hematophagous – or blood feeding – supplementing their diet with blood to help grow eggs.
Male mosquito mouthparts are much smaller in comparison, and do not allow them to penetrate skin. But the discovery of these fossils suggest this was not always the case.
Previously, the oldest known mosquito was dated to the Late Cretaceous period, which began about 100 million years ago. But this discovery has set the fossil record for the insect back further.
“Here we have one from the Early Cretaceous, about 30 million years before,” André Nel, a professor from the National Museum of Natural History of Paris and an author of the paper, told Cell Press.
It was the “earliest-diverging lineage and oldest occurrence of mosquitoes”, the paper said. Molecular dating suggests the insect originated even earlier, during the Jurassic period, but presently this fossil is the oldest identified member of the mosquito family.
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The discovery “suggests that not only were the earliest female mosquitoes hematophagous but males were also, in some cases”.
“Such behaviour would be surprising for a male mosquito” given that the males now feed on plant sap, nectar or honeydew, according to the paper.
Drinking blood might have been beneficial in reproduction for the males, and to increase their capacity to fly, but “why this behaviour was subsequently lost in males remains unknown”, the paper said.
One line of inquiry relates to plant evolution at the time. Around 5 million years after these mosquitoes lived, a “very important” diversification and spread of flowering plants began, eventually becoming the dominant variety of vegetation in the world, Huang said.
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Before then there were very few flowering plants, so it was possible that all mosquitoes relied on blood. Sucking blood “presents a very large danger,” with the potential for animals chasing or killing mosquitoes if they are noticed, Huang said.
Once flowering plants began spreading the males might have switched to drinking plant fluids to avoid this, he said.
The mosquitoes could be identified because they were discovered in amber, a medium that can, unlike other fossil types, preserve specimens true to their original form.
The team’s next step “is to examine amber that is even older” to see if they could discover even more about the earliest mosquitoes, Huang said.
