Oldest mosquito fossil comes with a bloodsucking surprise
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[December 06, 2023]
By Will Dunham
WASHINGTON (Reuters) - Hundreds of thousands of people worldwide are
killed annually by malaria and other diseases spread through the bite of
mosquitoes, insects that date back to the age of dinosaurs. All of these
bites are inflicted by females, which possess specialized mouth anatomy
that their male counterparts lack.
But it has not always been that way. Researchers said they have
discovered the oldest-known fossils of mosquitoes - two males entombed
in pieces of amber dating to 130 million years ago during the Cretaceous
Period and found near the town of Hammana in Lebanon. To their surprise,
the male mosquitoes possessed elongated piercing-sucking mouthparts seen
now only in females.
"Clearly they were hematophagous," meaning blood-eaters, said
paleontologist Dany Azar of the Chinese Academy of Sciences' Nanjing
Institute of Geology and Paleontology and Lebanese University, lead
author of the study published this week in the journal Current Biology.
"So this discovery is a major one in the evolutionary history of
mosquitoes."
The two fossilized mosquitoes, both representing the same extinct
species, are similar in size and appearance to modern mosquitoes, though
the mouthparts used for obtaining blood are shorter than in today's
female mosquitoes.
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"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. Males and unfertilized females will
eat some nectar from plants. And some males do not feed at all," Azar
added.
Some flying insects - tsetse flies, for instance - have hematophagous
males. But not modern mosquitoes.
"Finding this behavior in the Cretaceous is quite surprising," said
paleontologist and study co-author André Nel of the National Museum of
Natural History of Paris.
The delicate anatomy of the two mosquitoes was beautifully preserved in
the fossils. Both displayed exceptionally sharp and triangle-shaped jaw
anatomy and an elongated structure with tooth-like projections.
The researchers said they suspect that mosquitoes evolved from insects
that did not consume blood. They hypothesize that the mouthparts that
became adapted for obtaining blood meals originally were used to pierce
plants to get access to nutritious fluids.
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![](../images/120623PIX/news_f10.jpg)
An undated handout image of a view from below of the head of a
fossilized male mosquito, including elongated sucking-piercing
mouthparts, trapped in amber found in central Lebanon dating to
about 130 million years ago. Dany Azar/Handout via REUTERS
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Plant evolution may have played a role in the feeding divergence
between male and female mosquitoes. At the time when these two
mosquitoes became stuck in tree sap that eventually became amber,
flowering plants were beginning to flourish for the first time on
the Cretaceous landscape.
"In all hematophagous insects, we believe that hematophagy was a
shift from plant liquid sucking to bloodsucking," Azar said.
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 -
and hematophagy was later lost in males, maybe due to the appearance
of flowering plants, which are contemporaneous with the formation of
Lebanese amber."
Plenty of animals were present to provide blood meals: dinosaurs,
flying reptiles called pterosaurs, other reptiles, birds and
mammals.
The researchers said while these are the oldest fossils, mosquitoes
probably originated millions of years earlier. They noted that
molecular evidence suggests mosquitoes arose during the Jurassic
Period, which ran from about 200 million to 145 million years ago.
There are more than 3,500 species of mosquitoes worldwide, found
everywhere except Antarctica. Some become disease vectors
transmitting malaria, yellow fever, Zika fever, dengue and other
diseases. According to the World Health Organization, more than
400,000 people die annually from malaria - a parasitic infection -
mostly children under age 5.
"On the other side, mosquitoes help to purify the water in ponds,
lakes and rivers," Nel said. "In general, an animal can be a problem
but also can be helpful."
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
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