The tsetse fly is an annoying and sometimes deadly insect. After homing in on a victim, it lands on the skin and proceeds to feed on human blood. But no one has been quite sure of exactly how the blood-sucking nuisance manages to break through our skin and gorge itself, until now.
By using a new high-powered electron microscope, researchers have been able to image the mouthparts of the tsetse fly in exquisite detail, revealing structures never seen before. They show how the insect is able to chew through the skin to reach the blood, and how it manages to slurp it all up as it feasts on the good stuff.
Publishing their results in the journal Parasites and Vectors, the researchers took high-resolution pictures. These showed rows of sharp teeth and rasps on the tip of the proboscis, which allow the flies to scrape and tear their way through the skin in order to break into the delicate blood capillaries that lie below the surface.
After piercing the skin, the insect floods the wound with its saliva, which acts as an anticoagulant and keeps the blood flowing. The fly then slurps it up through a narrow tube located within the proboscis. Yet the structure of this thin tube took the researchers by surprise, as the images revealed that it wasn't smooth and pointed, but rather decorated with intricate finger-like projections with suckers.
“This was an unexpected finding – the textbooks just show a plain pointed end to the saliva tube,” said Professor Wendy Gibson, who coauthored the paper, in a statement. “We've no idea yet what this ornate structure is for – we haven’t come across anything like it in other bloodsucking insects such as midges and mosquitoes.”
Almost exclusively found on the African continent, there are around 29 to 31 different species of tsetse fly. Generally around the size of a common house fly, the insects are of importance to researchers because they spread parasites that cause sleeping sickness, or trypanosomiasis. The illness is caused by parasites called trypanosomes and is invariably fatal if left untreated.
The parasite is spread to humans when the tsetse fly spews its saliva into the wound it creates, so understanding the mechanism the fly uses to break the skin and suck the blood could aid in our understanding of how the deadly disease of sleeping sickness is spread.