The oldest-known fossils of mosquitoes have revealed a ‘bloodsucking surprise.’
Remains of two males frozen in amber 130 million years ago featured elongated piercing-sucking mouthparts seen now only in females – the only ones that bite.
The discovery is ‘a major one in the evolutionary history of mosquitoes,’ according to the team’s lead paleontologist.
The male specimens, these scientists argued, suggested an unlikely origin story for the blood-sucking mosquito: The insect may have evolved from a plant-sucking vegetarian ancestor.
Remains of two males frozen in amber 130 million years ago featured elongated piercing-sucking mouthparts seen now only in females – the only ones that bite
The specimens were unearthed in Lebanon, near the town of Hammana, researchers reported this week
The specimens were unearthed in Lebanon, near the town of Hammana, researchers reported this week.
‘Clearly, they were hematophagous [blood-eaters],’ said paleontologist Dany Azar of the Chinese Academy of Sciences Nanjing Institute of Geology and Paleontology and Lebanese University.
‘In all hematophagous insects,’ Azar said, ‘we believe that hematophagy was a shift from plant-liquid sucking to bloodsucking.’
Plant evolution may have played a role in the feeding divergence between male and female mosquitoes too, according to Azar, who served as lead author on the new study, published this week in the journal Current Biology.
When these two male mosquitoes became stuck in tree sap that eventually became amber, according to Azar and his colleagues’ analysis, flowering plants were beginning to flourish for the first time along the landscape of the Cretaceous world.
The fact that these earliest-known mosquitoes are bloodsucking males, Azar added, ‘means that originally the first mosquitoes were all hematophagous – no matter whether they were males or females.’
Azar and his team said they suspect the ancient mosquito mouthparts adapted for obtaining blood meals were once originally used to pierce plants to access nutritious fluids — and in some, they evolved back to plants.
‘Hematophagy was later lost in males,’ Azar speculated in a statement to Reuters, ‘maybe due to the appearance of flowering plants, which are contemporaneous with the formation of Lebanese amber.’
Researchers said that they suspect the ancient mosquito mouthparts that became adapted for obtaining blood meals were once originally used to pierce plants to get access to nutritious fluids — and in some, evolved back. ‘maybe due to the appearance of flowering plants’
Today, hundreds of thousands of people worldwide are killed annually by malaria and other diseases spread through the bite of mosquitoes, all bites inflicted by females.
‘Mosquitoes are the most notorious blood-feeders on humans and most terrestrial vertebrates, and they transmit a certain number of parasites and diseases to their hosts,’ Azar said.
‘Only fertilized female mosquitoes will suck blood because they need proteins to make their eggs develop,’ the scientist noted.
‘Males and unfertilized females will eat some nectar from plants. And some males do not feed at all,’ he added.
While some flying insects — tsetse flies, for instance — have hematophagous males, modern mosquitoes of roughly 3,500 species worldwide do not.
‘Finding this behavior in the Cretaceous is quite surprising,’ paleontologist and study co-author André Nel of the National Museum of Natural History of Paris told Reuters.
Researchers noted that the delicate anatomy of the two Cretaceous mosquitoes was beautifully preserved in the fossils.
Both displayed exceptionally sharp, triangle-shaped jaw anatomy and an elongated structure with tooth-like projections.
Plenty of animals would have existed to provide blood meals for these specimens: everything from dinosaurs to flying reptiles called pterosaurs to other reptiles, birds and mammals.
The researchers said these are currently the oldest mosquito fossils, but this kind of insect probably originated millions of years earlier.
They noted that molecular evidence suggests mosquitoes arose from about 200 million to 145 million years ago during the Jurassic Period.
Today, modern mosquitoes are found everywhere except Antarctica.
Some become disease vectors transmitting malaria, yellow fever, Zika fever, dengue and other diseases. According to the United Nations World Health Organization, more than 400,000 people die annually from malaria, a parasitic infection, primarily children under age five.
But: ‘On the other side, mosquitoes help to purify the water in ponds, lakes and rivers,’ Nel noted. ‘In general, an animal can be a problem but also can be helpful.’