According to a study in the Proceedings of the National Academy of Sciences (PNAS), a
fossilised mosquito has been discovered with its last blood meal
still preserved inside its abdomen, a revelation that effectively
extends the existence of blood-feeding in this group of insects by
approximately 46 million years.
Ralph Harbach, researcher at the Natural History Museum, London, was one of the members of an
international team of scientists that studied the ancient
blood-quaffing insect, which was preserved in a type of sedimentary
rock called oil shale from northwest Montana in the US.
Using a mass spectrometer and a scanning electron microscope,
Harbach and his team identified an iron-containing compound known
as haem, which is found in haemoglobin, in the stomach of the mosquito. This marks one of the first instances of finding
these particular molecules whilst also being able to identify their
location inside the stomach of a fossilised animal.
Commenting on this research coauthor Dr Harbach says: "This
fossilised female mosquito is an incredibly rare find. For it to
have died immediately after feeding and be preserved without
disruption to its fragile distended blood-filled belly means that
we have a unique opportunity to study whether complex molecules,
such as haemoglobin, can survive tens of millions of years.
"Our findings are a tantalising glimpse into the past. These
discoveries not only help us to better understand the evolution of
blood-feeding in insects, but also open up the possibility that
other complex biological molecules, under the right conditions,
might also be preserved through time."
The practice of animals feeding on blood is known as
haematophagy and occurs in around 14,000 insect species, such as
fleas and mosquitos. Haematophagy is also found in a variety of
other animals including birds, bats, fish and worms, indicating
that this feeding technique appears to have evolved independently
across different species, although fossil
evidence of this behaviour is extremely rare.
Dale Greenwalt, researcher at the Smithsonian's National Museum
of Natural History and lead author of the paper, adds: "This is the
only known fossil of a blood-engorged mosquito ever found and
represents the first clear evidence that some organic molecules can
be preserved in a fossil of this age. We made the assumption that
genetic material like DNA was not preserved. We didn't even attempt
to look at it because DNA degrades very quickly. Without question
there are probably other things contained in this fossil. We just
don't know what they might be."