The hagfish isn't so much a fish as a sentient mucus gland. It probably eats and swims too, but their primary function in the ecosystem is pretty much grossing out the other fish.
In response to physical attack or the curious sadism of a lab nerd, the hagfish secretes a microfibrous slime. When this goo is combined with water it expands into a cohesive, gelatinous muck. This is fortunate because fish are known to have contact with water with some frequency.
And the goo is downright amazing. Drop a single hagfish into a fish tank, and in seconds you'll have a tank full of taffy. A few drops of this stuff is sufficient to bind water dozens of times its own volume and, unlike a simple slime, the proteins it contains unravel to give it some tensile strength and durability.
It is custom designed to gum up the gills of any predators whose appetite is stirred by something that looks like a length of intestine basted in petroleum jelly.
This slime not only renders the hagfish nearly impossible to grasp, it prevents the thermal viscosity breakdown more common in fish using standard 10W-30. However, should a predator actually get ahold of the hagfish, it has one more trick left: It can wriggle free of their grasp by contorting its body into an overhand knot and sliding it toward the captive end.
This allows them to muscle against whatever is clutching them and use a little extra hagjuice to slide itself away. At that point, the predator usually realizes it's achieved little more than a mouthful of snot for its effort and swims away to consider the health benefits of vegetarianism.
Octopi are renowned for their defensive bag of tricks. Some can hide by squeezing into nooks a tenth of their width, even making a beer bottle suitable cover.
Others are expert mimics, morphing their color and appearance to appear foreboding like a seasnake, scorpion fish or... a flounder.
And, of course they have that whole "squirting ink" thing. But the veined octopus trumps all the others at their own game. It will cloak itself with its surroundings by squeezing into shells or any debris it can gather to form a makeshift fortress.
If the octopus can actually get ahold of materials like a coconut shell, it will take its defenses on the road. It will wrap itself in the shell and roll out on the ocean floor like a bunker on wheels. It's like driving a Hummer without looking like a douche.
It has adapted to this defense so well, that it has even dumbfounded Berkeley researchers by demonstrating the first evidence of bipedal movement in octopi.
Yes, it gets around like Squidward from Spongebob.
The sea cucumber holds the unenviable position of not only looking like a massive glistening turd, but looking equally as defenseless. When the humans name your species after a vegetable, you can tell you're probably not known for sharp teeth or claws. How does such a seeming affront to natural selection persist? Simple: This turd has skills.
Sure, some sea cucumbers (such as Holothuriidae atra) have defenses like toxic secretions, and others have developed reinforced body walls so that it takes twice as long to chew them to death (yes, it's the overcooked sausage defense).
But why bother with traditional defenses when you can vomit your lungs out of your ass?
More precisely, some sea cucumbers have white structures called cuverian tubules attached to a portion of their respiratory tree. When perturbed, the sea cucumber expels these adhesive threads out of its anus.
It provides a tender morsel for the predator to focus on instead of them. While it's busy chewing on its guts, the cucumber floats away. It's akin to a terrified cow spontaneously crapping out a filet mignon.
This seems a lot less insane from the sea cucumber's point of view; it can regenerate all those parts so it's no real loss.
Then again, even if you could regenerate a lung, it still seems like it'd hurt like hell to expel one from your ass every time there was an emergency. Is there a more fucked-up form of defense in all of nature?
Let's say you were chasing a guy. Like maybe he stole your laptop or something.
He's unarmed and you've backed him into a corner. What is the one thing he can do that would completely take your mind off the laptop so badly that he could escape amid your confusion?
If you said "fire a massive torrent of his own blood out of his eyeballs so hard it paints the alley red," then you should seek some kind of counseling. That is not a thing that a rational person thinks. But at least you know you're not the first to come up with the idea.
The horned lizard, when threatened, actually constricts blood flow to the head, building up pressure in the small vessels inside its eyes. At the right moment, they will forcibly rupture those vessels and propel a jet of blood up to five feet away. They can do this with surprising accuracy, a trait that its cousin, the "Bleeds-Like-A-Sprinkler-Head Lizard," sadly didn't develop until chronic anemia claimed the lot of them.
The purpose is not to make the predator stop and say, "Shit, did I just see that?" because apparently animals aren't as prone to such thoughts. No, the idea is that the blood is supposedly foul tasting to canine and feline predators.
This trait is akin to the "I'm going to lick my Lunchables so nobody steals it" defense you used back in grade school. Just with, you know, more blood-crying.
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And check out some more (lethal) animal defenses, in The 6 Deadliest Creatures (That Can Fit In Your Shoe). Or find out about some ridiculous ways humans defend themselves, in The 13 Most Irresponsible Self Defense Gadgets Money Can Buy.
And stop by our Top Picks to see new columnist, Cody, try to impress us by attempting to shoot blood out of his eyes.