There’s a fruit fly in my wine.
How upset should I be?
Is the whole glass ruined?
Well, it may have to do with whether or not the fly is male or female.
Living things can communicate using chemicals, and scents, from the “stay away” message
of a skunk spray to the “come pollinate me” allure of a rose, can be powerful ways
of sending messages.
Fruit flies, those tiny little pests buzzing around your bananas, also use chemicals and
scents known as pheromones to communicate with one another.
If fruit flies are releasing all of these chemicals out into the world, is
it possible that those same chemicals could ruin your glass of wine?
Well a group of researchers decided to answer this question!
And they won the 2018 Ig Nobel prize in Biology for their efforts, honoring
research that makes people “laugh and then think.” I kinda like that goal.
The team set up an experiment that asked a panel of people with very special noses to
see whether or not they could tell the difference between glasses of wine that had or had not contained
a fruit fly.
Specifically, they focused on female fruit flies of the species Drosophila melanogaster,
which produce a pheromone known as Z411-A1.
In their first test, the researchers took three empty wine glasses.
They placed a male fruit fly in one glass, a female fruit fly in another, and left the
third empty.
Then they let the flies walk around in the glasses for five minutes before releasing them and
allowing the panel of eight noses to sniff the glasses, without knowing which had contained
the flies.
They rated the glasses on “odor intensity,” from weak to strong.
Amazingly, the panel unanimously scored the glass that contained the female fruit fly as smelling
worse than the glass that contained the male fruit fly.
While I do find this to be remarkable, I will note that panel was very special, they were composed of
officials trained and selected to be a part of the official quality assessment of wines
at the Federal Institute for Viticulture in Freiburg Germany.
These weren’t just any panel of noses, these were very special wine-smelling noses.
The researchers also presented the panel with a series of control tests, to see whether or not they could detect
a synthetic version of the pheromone, which they could.
But for the really interesting test, researchers placed a female fly into a glass filled with
either water or white wine.
They left it there for five minutes, removed it, and then had the panel see if they could
tell the difference between water or wine with or without a fly.
And they could!
Further testing showed that the panel could detect as little as 5ng/L of the pheromone
in a glass of wine, describing it as an “unpleasant off-flavour.”
That’s five billionths of a gram in one liter.
That’s crazy, that's a super small amount.
This pheromone, Z411-A1 has been shown to elicit a “flight attraction” response in both males
and females of Drosophila melanogaster, but not in a closely related species, Drosophila
simulans.
This is cool because it means that it is a species-specific message.
So whether or not you finish your glass of wine depends on some extent to
if it is a female fruit fly, which could be emitting this pheromone.
But how are you supposed to tell if it's a female or a male fruit fly.
This is actually not that hard to do!
And it is a party trick that I whip out sometimes 'cause I am a terrible party guest.
Here, I’ve trapped a few fruit flies in my kitchen (using a no-kill trap!) and popped
them into the freezer for a couple of minutes so that they can chill out a little.
If we lay them out on this bed of ice to keep them cold, we can look at them with a macro
lens on my phone to see the differences.
In general, sterotypically male fruit flies are a little smaller than females.
The males also have darker coloration towards the end of their bodies.
If you flip them over, you’ll notice that the females have more of a pointed body shape
and the males have a more rounded end, with sort of rounded genitals.
Now of course it’s not just that simple and there’s some pretty cool genetics here too.
Fruit flies have four pairs of chromosomes: three of them are called autosomes and one
pair is the sex chromosomes.
Like mammals, fruit flies have X and Y sex chromosomes.
But unlike mammals, the autosomes play a role in determining the sex of the fruit fly too.
The sex of the fly is determined by the ratio of X chromosomes to autosomes.
A 1:1 ratio of X chromosomes to complete sets of autosomes typically produces a female fly,
and a 1:2 ratio of X chromosomes to complete sets of autosomes typically produces a male
fly.
This is regardless of whether or not a Y chromosome is present.
So XXY flies can be female, and XO flies (meaning there’s only a single X) can be male, though
the lack of sperm-related genes on the Y chromosome would cause it to be sterile.
There’s also a whole range of ratios which can lead to intersex flies, as well as male
or female flies with very low or high X to autosome ratios, and there are links to more reading
about all of that in the description down below.
I tell you all of this in the hope that next time maybe you will pause before swatting at that fruit fly
in your kitchen and ask if you can learn any science from
it first.
But regardless of the genetics, you probably shouldn’t let any flies in your wine.
Thank you as always to my Patreon patrons for supporting this video, sometimes your support goes to buying
new equipment and other times it goes to buying baggies of fake flies on the internet, and both things are important and appreciated.
So thank you so much for that support. Also thank you to you for watching.
If you enjoyed this video, share it with the wine lover in your life, and as always, remember
to go forth and do science.