A parasitic serpentine creature that seems ripped straight out of a Cronenbergian nightmare is murdering its way through the Great Lakes, and it's even found its way into Toronto's rivers.

If you've never heard of a sea lamprey, well, I'm about to make your day a lot less pleasant.

These eel-like jawless fish are best known for their absolutely terrifying concentric rings of teeth, which they use to latch onto their aquatic prey and drain them of their blood.

Photos of these alien-looking, suction cup-like mouthparts are enough to strike fear into most landlubbers, and descriptions of how they feed on other aquatic species only make them seem more unsettling.

It’s #InvasiveSpeciesAwarenessWeek
We support invasive removal projects on both land and water! Sea Lamprey are invasive fish that feed on bodily fluids of other fish. In 2021, TRCA removed 953 Lamprey benefitting ecosystems locally and the Great Lakes! https://t.co/nAuagUgzjF pic.twitter.com/fkTjWRClkB

— Toronto and Region Conservation Foundation (@TRCFDN) February 28, 2022

Those rings of keratinized teeth don't quite bite prey, acting more like articulated sawblades that grind away at tissue, working in conjunction with a sharp tongue that probes and stabs the victim. That blood stays flowing thanks to an anticoagulant, hemolytic, and cytolytic chemical secreted in its saliva called lamphredin.

But much more about these animals is not known by scientists, like how they got here, or if they even belong.

Sea lampreys were first noted in Lake Ontario almost two centuries ago, in the years after the opening of the Erie Canal. There is some question as to whether the animals actually had a native presence in Lake Ontario via its connection to the Atlantic, or invaded through artificial canal links with smaller bodies of water in New York and Vermont, where the species is also native.

Regardless of their origin, they are deemed an invasive species by the Province of Ontario.

Lamprey have been able to proliferate much deeper inland since the early 20th century, when the Welland Canal gave the species unobstructed access to the upper Great Lakes.

However long they've been in the Great Lakes, their populations are now rising sharply, and lampreys are a growing problem for commercial fishing. An early July piece in the Wall Street Journal about these blood-sucking menaces' impacts on the fishing industry in the Great Lakes has only further piqued the public's fearful curiosity.

“People just freak.” An uptake in #invasive sea #lamprey problems in the #GreatLakes https://t.co/mt80Cm9ND5 @jbarrchicago in @WSJ Happily from a greatly-diminished baseline (see @LampreyControl: https://t.co/4uhUA3gpY2) pic.twitter.com/WWGP9Vhnk2

— Andrew Revkin 🌎 ✍🏼 🪕 ☮️ (@Revkin) July 2, 2023

Fish caught in the lakes often bear the telltale scars of lamprey predation. In 2022, angler Dustin Pearl caught a massive pike while fishing from the dock wall of a downtown Toronto park, and it was suggested, based on video evidence, that the large fish had endured multiple lamprey encounters.

A massive pike caught in the midst of downtown Toronto - 📹 Dustin John Pearl https://t.co/LwSikYbRXy #Toronto #Fishing pic.twitter.com/MsXGfou1HK

— blogTO (@blogTO) March 23, 2022

Lakes are fed by rivers, and it should come as little surprise that waterways like the Humber River and Duffins Creek have also experienced surging lamprey populations.

@TRCA_HQ and @FishOceansCAN have been working on the annual sea lamprey trapping on Humber River and Duffins Creek. Trapping helps measure the effectiveness of @LampreyControl’s sea lamprey control program in Lake Ontario. Learn more: https://t.co/9R0EplpwQW pic.twitter.com/CUuV06Q0u3

— Toronto and Region Conservation Authority (@TRCA_HQ) July 16, 2020

The Toronto and Region Conservation Authority (TRCA) has been engaged in population control measures as lampreys infest the Humber River. Back in April, the TRCA captured roughly 7,000 of the parasitic creatures using traps in a span of only five days, breaking the record for an entire season by over 1,100.

The @TRCA_HQ reported record high trap catches on Humber River in 5 days; >7,000 sea lampreys were captured, crushing the full season record of 5,885 due to reduced control during the early days of COVID-19. We're back in force this year, targeting >230,000 larvae! 🎥Video: TRCA pic.twitter.com/ibghdOJKLX

— GLFC (@LampreyControl) April 20, 2023

I will leave you with the upsetting image of the wriggling masses of lampreys above as a reminder that, while orcas are causing terror among the ocean-going public, we have plenty of fearsome freshwater marine life to be worried about right here at home.