Aye-Aye vs Hagfish vs Velvet Worm: A Skeleton Finger, a Snot Bomb, and a 500-Million-Year-Old Glue Gun

I love a matchup where the contestants could not pick each other out of a lineup. Today we have a lemur with a witch's finger, a fish that turns into a bucket of slime when threatened, and a soft little worm that has been firing a glue cannon since before trees existed. They share no recent ancestor, no habitat, and no dignity. They are united only by the fact that each one made me say 'no thank you' out loud. Let's rank them on the only metrics that matter: how cool, how weird, and how gross.

The aye-aye: a primate that knocks before it eats

The aye-aye (Daubentonia madagascariensis) is the world's largest nocturnal primate, and it forages by tapping on tree bark up to eight times per second, then listening with enormous bat-like ears for the echo of a hollow tunnel where a grub is hiding. This is called percussive foraging, and it eats up between 5 and 41 percent of the animal's foraging time. It is the only primate thought to locate prey this way.

The weird part is the hardware. The aye-aye's middle finger is a thin, almost skeletal digit with a ball-and-socket joint, which it uses to hook larvae out of the wood it just gnawed open with rodent-like, ever-growing incisors. A primate with beaver teeth and a chopstick finger should not exist, and yet here it is, in Madagascar, where local folklore often treats it as an omen of death to be killed on sight. Rough crowd for a creature whose only crime is having the worst hands at the party.

The hagfish: defense by instant snot

The Pacific hagfish (Eptatretus stoutii) is an eel-shaped, jawless fish that lives in the deep, photographed here at 150 meters down. Its signature move is the single most disgusting escape in the ocean: when something bites it, it releases a protein that, on contact with seawater, expands to roughly 10,000 times its volume in about 0.4 seconds. A would-be predator gets a mouthful of attacker and ends up with a face full of gel, gills clogged, dinner abandoned.

Then comes the part that is somehow both cool and cursed. To get the slime off itself, the hagfish ties its own body into an overhand knot and slides the knot from head to tail, scraping itself clean. It uses the same knot trick to gain leverage and tear off chunks of food, since it has no jaws. Oh, and it is the only known living animal with a skull but no vertebral column. A face, a knot, and a panic button that fills the room with goo.

The velvet worm: a living fossil with a glue gun

The velvet worm (Onychophora) is the one I respect the most, partly out of fear. Its body plan has barely changed in something like 500 million years, which means this little plush caterpillar-looking thing was workshopping the same strategy back when 'land animal' was a hot new idea.

That strategy is a slime cannon. From two oral papillae on its head, it fires adhesive jets at 3 to 5 meters per second while the nozzles oscillate at 30 to 60 hertz, so the streams whip back and forth in mid-air and weave a net over the prey. The glue hardens, the prey stops moving, and the velvet worm strolls over to liquefy the insides and slurp them out. A 2 to 8 centimeter softie that builds a net out of high-velocity spit is exactly the kind of thing evolution should require a permit for.