Saturday, 4 February 2012

The Oldest Vampire On Earth

The 20 million year old bat fly preserved in Dominican amber
Flies are considered by most people to be foul pests. They do everything from ruin picnics to giving rather painful, swollen bites, particularly in the case of the horsefly. Most species of fly are detrivores, who eat scraps, carrion and even faeces; some are parasitic, feeding off other organisms. One of the nastiest is the bat fly. While small, coming in at just 3 millimetres in length, it goes wherever it pleases, feeding off whatever it can.

The bat fly is also unusual as it is one of the few species of insect which co-evolved with another group of creatures, the bat. It mainly lives in caves inhabited by the New Zealand lesser short-tailed bat, feeding off their blood in a rather vampiric lifestyle. Now a team of palaeontologists have found evidence to suggest that these tiny flies have been carrying out their parasitic existence for at least 20 to 30 million years. The Dominican Republic is famous for its Miocene amber, many pieces of which contain preserved insects.

Everything from beetles to scorpions have been found within the fossilised tree resin. Now the palaeontologists, led by Professor George Poinar from Oregon State University, have found the first ever record of the bat fly in the Earth's evolutionary history. 'Bats are mammals that go back about 50 million years, the only true flying mammal, and the earliest species had claws and climbed trees. We now know that bat flies have been parasitizing them for at least half that time, and they are found exclusively in their fur.'

What is more, the team found that the bat fly was also carrying the malaria bacterium Plasmodium. A recent study has shown that the modern strain of malaria evolved around 20,000 years ago. This fossil has set the new baseline for its evolutionary heritage as well as that of the bat fly, but it is possible that both species have been around for much longer. Bats evolved around 50 million years ago, creating the opportunity for its various parasites.

While this specific genus of fly is now extinct, the malaria bacterium is carried by many different species of insect. This new fossil is just one carrier. What is most unusual is the fact that the fly has been found in amber in the first place. 'Bat flies only leave their bat in order to mate,' states Poinar, 'and that's probably what this specimen was doing when it got stuck in some sticky, oozing sap.' New fossil discoveries will increase our knowledge of their early lifestyle and their evolutionary history.