WTF Fun Fact 12806 – Greenland Sharks Are Blind

There are an awful lot of people who want to know “Are Greenland sharks blind?” That’s probably because any time you hear about the species Somniosus microcephalus it’s in relation to the parasite that lives in their eyes.

So, ARE Greenland sharks blind?

While we don’t know exactly what percent of Greenland sharks are blind, scientists do believe that many, if not most, at at least partially blind because of the parasites.

And these sharks already had a bad reputation to begin with. According to Oceana (cited below), “Like many other polar fish, their flesh contains high concentrations of natural antifreeze. According to a handful of reports, Greenland shark meat is so toxic it can make sled dogs vomit and ravens act drunk.”

But people aren’t big shark fans anyway, so their toxicity is very likely overstated. Oceana continues: “But this is likely a case of false advertising. The antifreeze compound in their tissue is toxic, but only mildly — an adult would have to eat around 20 kilograms (44 pounds) of shark at one sitting just to feel woozy.”

Ok, we’re blaming you if you eat that much shark meat.

Anyway, back to the blindness.

The sharks tend to be seen as ungraceful (the word “bumbling” has been used to describe them). But they’re born with small eyes to begin with and then lose their vision due to the parasitic crustaceans which measure just 3-centimeter-long – Ommatokoita elongata. Oceana states that “Each eye usually hosts one adult female along with several larvae. They nibble away at the shark’s cornea tissue, destroying its vision in the process.”

As a result, the sharks see in a haze and can only sense patterns of darkness and light.

However, they have a keen sense of smell, so they don’t have too much trouble grabbing dinner.

And dinner for this shark, which is a scavenger, is rotting meat.

Why do these sharks get such a bad rap?

Aside from looking kind of gross with the whole “crustacean feasting on their eyes” thing going on and harboring toxic chemicals in their skin, the sharks have a reputation as one of the “laziest” creatures.

Frankly, we’d prefer a lazy shark to a really energetic go-getter!

They get this reputation in part because the Greenland shark isn’t very fast (not surprising since they’re partially blind) as well as one of the world’s biggest sharks (reaching 24 feet long).

Somniosus microcephalus moseys along at around 1.5 miles an hour. But that’s also in part because of the frigid waters they live in. They are perfectly happy to live their lives in water as cold as 29 degrees F.

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Source: “Maligned as Lazy and Toxic, Greenland Sharks Are Smarter than You Think” — Oceana

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