How does your blood taste for a mosquito? Researchers recently discovered that the delicious taste of human blood sends sensory neurons that ignite like fireworks in a mosquito’s syringe-like “tongue”, a piercing mouthpiece known as a stiletto.
Only female mosquitoes feed on blood and only to feed their developing eggs – otherwise they drink flower nectar. To better understand the attraction of mosquitoes to human blood, scientists genetically modified Aedes aegypti mosquitoes so that the insect’s taste-related neurons emit fluorescent light during activation.
The researchers then used fluorescence microscopy to see neurons firing in the mosquito’s stilettos as the insects feed on real human blood and other liquid meals. This is according to a study published October 12 in the journal Neuron.
Connected: Why human blood drives mosquitoes wild
Biologists studying mosquitoes often do so at the expense of their own skin, allowing the insects to bite them to reveal blood-feeding behavior in action. For the new study, the scientist turned to a device called the BiteOscope. The BiteOscope was developed by another research team to “give scientists and their skin a respite”. It’s a small open platform with a membrane over pockets that hold liquid. It offers mosquitoes the opportunity to drink themselves in an environment that mimics a skin-covered host and enables scientists to observe mosquito feeding behavior and collect data without sacrificing their own skin, the developers of bitOscope wrote on Dec. September in eLife magazine.
The mosquito researchers observed the activity of neurons in mosquito stylets as their subjects approached nectar, blood and an artificial “blood” mixture of glucose, sodium chloride and sodium bicarbonate in concentrations “in the range of standard blood values for vertebrate species” for the study. The artificial blood also contained adenosine triphosphate (ATP), a compound in the blood that carries energy to cells and whose previous studies have shown them to be attractive to mosquitoes, the scientists reported.
“To understand the properties of blood-sensitive neurons, we needed a stable mixture with a known composition that could reliably activate blood-sensitive neurons in the stiletto,” said lead study author Veronica Jové, PhD student and Howard Hughes Gilliam Fellow of the Medical Institute (HHMI) at Rockefeller University in New York City.
(Photo credit: Prakash Lab)
“Special Mystery Stuff”
In the presence of real blood and the lab-made mixture, a subset of mosquito stiletto neurons – roughly half of the 40 found in a female mosquito’s stiletto – flared brightly, but those neurons were not activated at all on the taste of the sweet nectar, according to the study .
However, are you deciphering exactly how our blood might taste to a mosquito – are we sweet because blood contains glucose? Salty because of sodium chloride? Somewhere inbetween? – is difficult, said study co-author Leslie Vosshall, a professor and researcher at HHMI at Rockefeller University.
“There is nothing like it in human experience,” Vosshall said in a statement. That’s because one of the key components that mosquitoes draw in the blood is ATP, which has no “taste” on the human tongue, Jove told Live Science in an email.
Vosshall confirmed this firsthand by trying the laboratory-made ATP-infused mixture himself.
“It has no taste at all,” she said in the statement. “ATP is that special mysterious stuff that tastes like nothing to humans. But it has to be incredibly exciting and rewarding for the mosquito.”
(Image credit: Shutterstock)
People experience five basic tastes: sweet, sour, umami, bitter and salty, said Jové. While researchers couldn’t say exactly which aromas tickled mosquitos’ tastes individually, we can share the appreciation for saltyness – our perception of salty taste is triggered by sodium chloride, or NaCl, which was present in both the blood and the laboratory blood, as the The mosquito’s stiletto neurons fired, Jové said.
Determining what makes human blood so delicious for mosquitoes could be a first step towards creating deterrents that make us less tasty and thereby reduce our chances of being bitten, the researchers said in the statement. Identifying these factors could also shed light on diseases like dengue and zika that mosquitoes spread when they feed on infected people, Jové told Live Science.
“Understanding how mosquitoes taste blood to initiate blood-feeding behavior is fundamental to understanding how vector-borne diseases are transmitted around the world,” she said.
Originally published on Live Science.