This week’s post is not a direct user submission, but it’s a picture that’s so neat that I wanted to highlight it with it’s own blog post.
The picture is pretty self-explanatory. It’s a picture of a mosquito attempting to feed on cheese, which is definitely not a natural food. Mosquitoes are pretty well adapted to a liquid diet, specifically blood. We’ve talked about how they keep their host’s blood from clotting, but less about how they find their hosts.
Mosquitoes can’t obtain any nutrition from cheese because their saliva is highly adapted to keep blood from solidifying, and can’t really break clots up once they form. So this mosquito is just probing the cheese, looking for a vein.
So what’s going on here, and why do I think this picture is really neat?
I guess the first thing we need to talk about is cheese, and how it’s made.
What is cheese?
Cheese is essentially curdled protein. The simplest cheese to make is called Paneer, which is made by precipitating proteins out of milk using an acid like vinegar or lemon juice. The cheese is strained, and the solids coagulate into an edible solid. All cheese is made more or less the same way, making a dairy product acidic so the proteins precipitate into something edible.
Not all cheese is made the same way, and different cheeses are made with different acids. Paneer is made without bacteria, but most cheese gets it’s acid using bacteria. Compounds produced by the bacteria are what give cheese it’s specific flavor. Different bacteria communities give different cheeses their flavor, and some are even flavored by mould. Or flies. Or mites.
Really, the biology of cheesemaking is fascinating.
How do mosquitoes find their hosts?
Mosquitoes find their hosts using chemicals produced by the hosts. Everybody has their own particular funk, no matter how well you bathe. It’s mostly a mixture of waste products, like carbon dioxide, lactic acid and ammonia…but there are other compounds in there as well.
Humans, like virtually everything else on the planet, are not a single organism. Instead we’re a holorganism, which means that we exist as a part of a community of symbionts. These symbionts do a lot of things, from producing vitamins to outcompeting pathogenic bacteria.
These symbionts also produce waste products, some of which are detectable to people in the form of body odor. Mosquitoes use these odors to cue in on hosts, and they can be attracted to human body bacteria which are grown in petri dishes.
So bacteria make stuff mosquitoes use to find their hosts.
Mosquitoes, body odor and cheese
So if you put it all together, you’ve got a product that’s produced by bacteria…and many cheeses have their own particular odor. Some even smell like body odor.
It’s been known for awhile that some mosquitoes, namely the malaria mosquito Anopheles gambiae, are attracted to cheese. Specifically, they like Limburger cheese. This species prefers to bite people’s feet. Limburger cheese tends to have a very foot-like odor because it’s made with bacteria that are very closely related to the ones which make your feet stink.
The compounds produced by the Limburger cheese are close enough to human body odor to confuse mosquitoes. They find what they think is a human foot, land and try to feed because they can’t tell the difference.
However, this is not a malaria mosquito. The genus Anopheles has a very characteristic feeding behavior, and feeds at a 45* angle to it’s host as pictured above. Other mosquitoes feed with their butts held parallel to their hosts.
The mosquito pictured above is one in the genus Aedes, a group of mosquitoes we’ve discussed before in the context of biotechnology. It’s coloration is pretty characteristic, although I don’t think it’s Ae. aegypti or Ae. albopictus.
The cheese pictured above is also not Limburger cheese. I’m not going to give the exact brand (it was given in the Facebook thread if you’re interested), but the type of cheese it’s feeding on is Edam cheese according to Almeida.
Upon reading the thread, I did a quick literature search to see if this cheese had documented to pair with this mosquito. While it’s known that Anopheles pairs well with Limburger, and while there’s been a lot of research into the compounds that Aedes mosquitoes are attracted to, I wasn’t able to find any papers on whether there are any cheeses attractive to Aedes mosquitoes.
So, to say the least, this is an extremely unusual situation…and I’m really excited to see what sorts of discussion it will spark among Entomologists on social media.