When going out for sushi, you usually hope you get what you pay for. Some of us aren’t fish experts to know what types of fish look like, feel like, or taste like—and, we assume that when we order salmon or tuna, we’re getting salmon and tuna. It turns out, this isn’t always the case. Thanks to some molecular biology students, we now know that some sushi restaurants are out here scamming us all—and, it’s wildly f—ked up and gross.
Dr. McDonald, a biology professor at Fanshawe College in London, Ontario, recently tweeted about an experiment her students were conducting using fish DNA. They were to sequence the fish DNA from restaurant sushi orders and see if the fish actually match the ones labeled on the menu. Dr. McDonald claims that she was looking for a way to “spice up” the lab experiments in her class and thought that this would be a pretty awesome assignment to conduct.
Dr. McDonald told Bored Panda that students had to perform a process called DNA sequencing on their samples.
“Identifying species by their sequence barcode is almost exactly like going shopping. You pick out the items you want, some of them have price stickers on them, some of them don’t, and you take them to the cash register. As each item’s tag is scanned, the barcode on the item is the identifier: each item has a different barcode.
When scanned, the exact item and that item’s price is displayed on the register’s screen as long as it’s in the database. With living organisms, each major group of organisms has a well-established “barcode” in animals we use a gene called co1, in plants we use a gene called rbcL, in fungi weuse a gene called ITS, etc.
A gene sequencer has the ability to read all of the letters of the genetic code between two primers, that act like target probes. They restrict the region you’re generating the sequence for, instead of getting the entire genome. Once the sequencer has given you all of the letters between your primers, you run that through the barcode database and it will tell you what species that barcode is from. It’s really nice because it can work on a very small piece of tissue, instead of relying on identification based on the entire, intact, organism.”
Dr. McDonald explained on Twitter how the experiment would go down:
So on Friday my Molecular Bio students did a lab about fish fraud. Their Super Important Homework Assignment (TM) was to go out for sushi and take a small sample home in a ziploc bag (EAT THE REST. Wasting food is uncool). Label the supposed fish, put it in the freezer.— Dr. Jen M (@AwesomeBiota) April 1, 2019
Bring it into the lab next time on campus, put it in our "class freezer" on the bottom shelf.— Dr. Jen M (@AwesomeBiota) April 1, 2019
On Friday, we took those samples, minced them so small it would make world-class chefs shed tears of envy, and extracted the DNA from the fish. Amplified the CO1 gene using PCR.
Notoriously, students are pretty bad at PCR. Then again, EVERYONE is pretty bad at PCR. It's the kind of thing that you have to practice a lot, it's hard to get a whole class to practice a lot (resources and time and all that), so we use "instructor samples" downstream.— Dr. Jen M (@AwesomeBiota) April 1, 2019
But this time? HOLY BANANAS THEY ALL GOT RESULTS. I ran the gels today for them & posted results on our course website. Kids, I'm so excited for what these sequences will reveal. The results were *so good*. Better than I've seen in a very long time even considering my own results— Dr. Jen M (@AwesomeBiota) April 1, 2019
Thursday I'll send them for sequencing and we'll collectively cross our fingers to see what we get. Here's the gel images in case you're curious. Keep in mind this is the...3rd PCR most of these students have set up, and some wells are negative controls. pic.twitter.com/nhVQHtwgrP— Dr. Jen M (@AwesomeBiota) April 1, 2019
1 of the results, which I think is the one in the L gel, top row, 2nd well from the R, is one that I found *exceptionally unlikely* that it would work. The origin of that sample was from a dogfish shark another one of my classes had dissected. Prior to processing, it ate a meal!— Dr. Jen M (@AwesomeBiota) April 1, 2019
Since it was half-a-fish (no head) and had no other distinguishing characteristics other than "silver", I thought it would be neat to see if we COULD get a DNA sample out of it. Turns out...we can't. At least, not with the protocol we used.— Dr. Jen M (@AwesomeBiota) April 1, 2019
So now my class of 16 will have a set of samples to look at real-life prevalence of food fraud in the seafood industry. What are we going to find? No idea! But I'm willing to put $5 on that NOT being "red tuna". The tilapia is also almost certainly red snapper. We'll see! ????????— Dr. Jen M (@AwesomeBiota) April 1, 2019
Then, she got the results and they were…horrifying.
OH BOY OH BOY.— Dr. Jen M (@AwesomeBiota) April 5, 2019
I just got the results back from my class' foray in sequencing fish samples. ARE YOU READY? They're a mind-bender. https://t.co/O7yBCHEQg4
One student sequenced some Red Snapper, which turned out to be Tilapia. The other student thought he had Atlantic Salmon, which came back as Rainbow Trout.
Josue sequenced some red snapper. I put money on that being tilapia and...I was right. Someone owes me $5.— Dr. Jen M (@AwesomeBiota) April 5, 2019
His lab partner, Juanni, sequenced Atlantic Salmon. Comes back as Rainbow trout. Unsurprising. Not the same species AT ALL, but unsurprising.
Two students thought they were sequencing Rainbow Trout, but, it turned out that one was Rainbow Trout and the other was straight up salmon.
David and Nicolas both sequenced what they thought was Steelhead trout (aka Rainbow trout). David's was smoked, Nic's not.— Dr. Jen M (@AwesomeBiota) April 5, 2019
Nic's was rainbow trout.
David's was coho salmon.
One student, Reena, sequenced grocery store cod—which turned out to be on-point. But, Sydney sequenced Pacific Cod, which ended up being Atlantic Cod.
Reena sequenced what was labelled (on the box I bought at the grocery store, no less) Icelandic Cod (MSC-certified).— Dr. Jen M (@AwesomeBiota) April 5, 2019
It was. Thank God.
Sydney sequenced what was labelled (again, ON THE BOX purchased at the grocery store) Pacific Cod.
It was Atlantic Cod. (CRINGEEEE!!!!!!)
Jade got down to the nitty-gritty of sushi restaurant fraud.
Jade sequenced what the sushi restaurant (who shall remain nameless...it's probably not their fault) called red tuna.— Dr. Jen M (@AwesomeBiota) April 5, 2019
IT WAS TILAPIA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Moe sequenced White Tuna—which, ended up being a completely separate tuna.
Moe sequenced one of the two samples (from different restaurants) labelled "white tuna". Often another name for albacore tuna.— Dr. Jen M (@AwesomeBiota) April 5, 2019
It was yellowfin tuna. (NOT the same species!! A trade upwards)
Evalyne sequenced what was also supposed to be White Tuna—but, it ended up being Escolar, which Dr. McDonald pointed out could be very dangerous to people who cannot stomach this.
Evalyne sequenced the other sample of "white tuna". That was the one that I brought in, that I theoretically would have eaten if I actually liked and ate "white tuna" (I think it's gross).— Dr. Jen M (@AwesomeBiota) April 5, 2019
It was escolar.
THIS IS DANGEROUS. Can cause extreme gastrointestinal distress.
Last but not least…there was one mystery among the samples.
Last but not least of successful sample runs, we had one that makes my skin crawl. It was a sequence that came back with a bunch of "unknown bases" (a bit of cleaning up will help immensely) but I worked with what I had and ran it through the database. Was *supposed* to be Salmon— Dr. Jen M (@AwesomeBiota) April 5, 2019
This salmon was not from a restaurant, but was instead purchased from the seafood department of a local grocery store. Again, to remain nameless. This was purchased from a counter, someone reaches in and grabs the fish, puts it in a bag, sticks a sticker on it, pay by the pound.— Dr. Jen M (@AwesomeBiota) April 5, 2019
Of a gene approximately 650 base pairs long, I was hoping to get a workable sequence of at least 500 base pairs. This one only had 200 clean pairs before I go through the file to improve the sequence generated. So short compared to expected of "working material".— Dr. Jen M (@AwesomeBiota) April 5, 2019
Body louse.— Dr. Jen M (@AwesomeBiota) April 5, 2019
I think I might vomit in my mouth a little.
I hope this is a mistake. HOPE TO ANY GOD FROM ANY RELIGION that this is a mistake.
I hope that this somehow becomes a fish sequence when I clean it up a bit. BUT BODY LOUSE.
Which, basically means they were eating insects(!!!)
This wasn't a piece of garbage from a market. This was from a "salmon fillet" that someone paid good money for, cut some off before they cooked it, put it in saran wrap & brought it in.— Dr. Jen M (@AwesomeBiota) April 5, 2019
Think about how much there must be in that sample to override fish DNA!
Anyway, I don't know if any of my students are nearly as enthralled as I am about the results of this experiment. I'M THRILLED.— Dr. Jen M (@AwesomeBiota) April 5, 2019
16 students, 13 decent bands on the gel.
Of those, we had 9 with pretty decent sequences. THAT'S NOT BAD.
Of those 9, TWO WERE LABELLED CORRECTLY.
So if you "are what you eat" and you like seafood? You have no idea what you are because nothing is labelled properly. If you want to know what you're eating? Make sure it's from a certified sustainable fishery. They know what they're fishing, and know what they're doing.— Dr. Jen M (@AwesomeBiota) April 5, 2019
People were blown away at the experiment, and just as many were grossed out.
As a lover of science this is awesome! As a lover of seafood this is terrifying ????— Chris Brown (@cferak) April 6, 2019
Okay cool never eating sea food again pic.twitter.com/ifGnBulppO— Alonso Delgado (@wildlife_bioGuy) April 5, 2019
I'm actually shook. Like this is awesome, but also I will never be able to trust any seafood ever again— Tina Lasisi (@TinaLasisi) April 6, 2019
I was not ready.— Gwen C. Katz (@gwenckatz) April 6, 2019
Science for the win (with a side of OMG) - thanks for sharing! ???? ????— Summer Burton (@selysia) April 6, 2019
Woww! Such a cool experiment!! Where is the Food and Consumer Safety department?? ????♀️????♀️????♀️????♀️— Tiziana A. Gelmi Candusso, PhD (@t_gelmicandusso) April 6, 2019
Scientifically wonderful!— Margo Buisson (@mytwoboysmomma) April 7, 2019
As a lover of seafood... yuck!!????
I might never buy fish or scallops again! Thank you for being a terrific teacher, though....