The Deep-ocean Anglerfish Catches Prey With the Lure on Its Head

Anglerfish have got an angle all right, but it's definitely not to win anyone over with their spooky good looks. Rather their end game is to attract their prey using a form of fishing known as angling, where an angle (hook) is used to lure in and catch an unsuspecting fish. Yep, just like a fisherman sitting with a pole in hand, anglerfish do indeed fish ... except they do it from the ocean floor. No tackle box or bait needed.

The carnivorous female anglerfish wait patiently in the depths of the sparsely populated deep sea to literally lure in their next meal. They wiggle and "angle" a rod-like extension of their dorsal spine that protrudes from their head and emits light. Once their prey comes close, the female strikes and snags them, using her large, pointy teeth to chomp them up, even if they are twice her size. You gotta admit, that's some seriously self-sufficient fishing.

And in a scientifically groundbreaking 2018 video, scientists captured images of a female with numerous thin filaments extending from her body in addition to her main dorsal appendage. These filaments also emit light, creating a bioluminescent web of whiskers to attract and surround their prey:

Where Do Anglerfish Hang Out?

Some species of anglerfish live in shallow, tropical waters, but the ones that peak the interest of scientists are the ones that live in the deep, murky depths of the ocean — some as deep as 16,400 feet (5,000 meters).

Ted Pietsch, a professor at the School of Aquatic and Fishery Sciences at the University of Washington and author of Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea, has been studying the elusive anglerfish almost his entire career. He reports by email that, "There are about 166 species so far, but new ones are still coming up. They live so deep that we don't really have a good idea of how big they actually get. We send nets down to collect them, and the deeper we go the larger specimens come up."

But how do they manage to stay so close to the ocean floor at such depths? Pietsch shares that most anglerfish, along with some other deep-sea fish, don't have a swim bladder — a gas filled sac that helps fish stay afloat without the need to constantly swim. The lack of a swim bladder not only helps them stay near the bottom, it also conserves energy — energy that's at a premium given the difficulty of finding a meal so far down.

Gender Plays a Huge Role

Female anglerfish are definitely running the deep-sea show. Pietsch says "Most females aren't much larger than your fist, but other species (most notably the Certias species) are close to 4 feet (1.2 meters) long. A male anglerfish on the other hand is usually an inch (2.54 centimeters) or so long. In the most extreme cases, the female is 60 times the length and about half a million times as heavy as the male."

The male, who has no way to feed itself, must rely completely on the female for survival. "They (the males) have tiny pincher-like teeth on the tip of their snout, and they bite on to the female," says Pietsch. Afterward, the two actually merge and become one. But it's not because they're in love. "The blood flow from the female to the male provides the nutrients. If they don't find a female, they're toast," says Pietsch. Scientists believe the female emits alluring pheromones that the male can sniff out with his proportionately large nostrils. Their relationship really is quite unique, Pietsch says. "These are the only animals in the world that attach permanently and exchange fluid."

Scientists note that the size difference is a survival mechanism that allows them to thrive on the limited deep-sea menu. If they were both large, it would take a whole lot more food and energy to keep them alive and their unique reproductive cycle going.

These creepy looking deep-sea dwellers take sexual parasitism to a whole new level. While the female has to carry the little guy around and keep him fed, she's also getting a pretty good deal out of it too. There's no need to put herself out there to attract a loyal partner — she's got a sperm bank (or two or three or even six) available 24/7. Even though the male is small, he's always got his testes ready and available to fertilize her eggs.

Can You Eat An Anglerfish?

Luckily for anglerfish — and the ecosystem — you won't find them making an appearance on anyone's dinner plate. And it's not just because they're elusive and scary to look at; Pietsch says their fatty and oily composition doesn't make very tasty. Well, that is unless you're talking to a sperm whale. Anglerfish remains have been found in whales' stomachs, and they seem to be the main predator of the larger anglerfish species.

While it's extremely challenging to find anglerfish and they're still somewhat of a mystery, scientists are entering a new realm of studying their behavior. And while their scary looking teeth and angry face may not look appealing to most of us humans, they continue to light up the deep sea, attracting an oh-so-lucky male anglerfish right along with their next deep-sea dinner.