Scientists have unearthed the oldest-known mosquito fossils, revealing a bloodsucking surprise. The fossils dating back 130 million years to the Cretaceous Period reveal that both male and female mosquitoes were once blood-feeders. The findings challenge the current understanding that only female mosquitoes suck blood and could help to explain how male mosquitoes find human bodies to swarm over for a chance to bite.
The researchers stumbled upon the fossils of two male mosquitoes near Hammana in Lebanon, which were preserved in resin that trapped them. At the same time, they drank the blood of dinosaurs and other prehistoric creatures. The fossils contain mouthparts that resemble modern-day female mosquitoes, indicating that the insects were indeed blood-feeders.
But the scientists were also surprised that the insects’ abdomens were bulging with a reddish liquid. Tests revealed that the liquid was a chemical compound called hemoglobin, which contains iron, an essential nutrient. Hemoglobin is known to be preserved in amber, a hardened resin, but it has never been detected in mosquitoes before.
The scientists used a high-tech microscope to scan each fossil and examine its composition to confirm the findings. They found that the fossils were utterly devoid of hemoglobin and other proteins. They also tested the specimens’ body fluids for phosphate and nitrogen. Both chemicals are commonly found in vertebrate blood and are expected to be present when a creature has consumed blood. The team believes that the mosquitoes ingested the blood of dinosaurs and other prehistoric animals for their nutrients.
The fossils also contained traces of other chemicals, such as amino acids and glucose, which are typical in the digestive tracts of hematophagous insects. But most important of all was the discovery that the abdomens of both fossils were filled with a reddish liquid that matched the composition of hemoglobin.
Until now, the fossil record of blood-feeding insects is sparse. Although some insect fossils have been classified as hematophagous based on their taxonomic affinities with extant hematophagy species, direct evidence of hematophagy has only been observed in four insect fossils in which malarial parasites (such as the protozoan Plasmodium) and trypanosomes have been identified.
The discovery of the blood-engorged mosquito in the Kishenehn shale in Montana is essential to mosquito evolution and ecology research. For example, it sheds light on why male mosquitoes don’t automatically swarm toward humans, which requires specialized neurons and brain structures to be turned on by genetic switches. Further, the study suggests that understanding how these male mosquitoes can find people might help scientists develop new tricks for fighting malaria and other diseases spread by mosquitoes.