We’re gonna talk about hagfish today, since it is Their Day
Hagfish are vertebrates, but they have no vertebrae! They lack bones entirely, with just a cartilaginous skull and a notochord (making them the only animal with a skull and no spine). They also have no eyes and no jaw. They also like to cuddle.
Exactly where they fall on the tree of life has been an interesting topic. Historically, they were placed as the sister-group to vertebrates; the vertebrate that diverged the earliest, and remained very primitive-looking. However, with new fossil evidence and DNA analysis, we’ve figured out that they are closest related to the lamprey, another jawless fish that does have eyes and bones! Which means the ancestors of the hagfish did as well, but somewhere along the line they decided, “screw it, I’m going back to being a Worm”.
The hagfish spends most of its time at the bottom of the ocean, sniffing around for prey. Although they do actively hunt and catch their own food, it’s much easier to eat things that are already dead, so they’re frequently seen snootling around whalefalls and bait set out by scientists, where they feed by rapidly spinning around until they’ve bored a hole straight through the skin and can get to the tasty insides!
But wait, how does a jawless animal feed at all? It just has a little :O face with no teeth!
Well, great news! That cute little :O isn’t it’s mouth! That’s it’s nose! It’s mouth is underneath.
Being a squishy little guy with no teeth or eyes, defending itself is kind of difficult. Luckily, no one wants to eat a hagfish, because they are gross af. They secrete a very thick slime that chokes predators. About 4% of a hagfish’s body mass is pure slime. This slime is also apparently useful to humans, because it contains strands that are stronger than nylon, offering a way to make more durable and environmentally friendly fabric!
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