The Horrors of Anglerfish Mating

Wikimedia Commons

When you think of an anglerfish, you probably think of something like the creature above: Big mouth. Gnarly teeth. Lure bobbing from its head. Endless nightmares following. 

During the 19th century, when scientists began to discover, describe, and classify anglerfish from a particular branch of the anglerfish family tree—the suborder Ceratioidei—that’s what they thought of, too. The problem was that they were only seeing half the picture. The specimens that they were working with were all female, and they had no idea where the males were or what they looked like. Researchers sometimes found some other fish that seemed to be related based on their body structure, but they lacked the fearsome maw and lure typical of ceratioids and were much smaller—sometimes only as long as six or seven millimeters—and got placed into separate taxonomic groups.

It wasn’t until the 1920s—almost a full century after the first ceratioid was entered into the scientific record—that things started to become a little clearer. In 1922, Icelandic biologist Bjarni Saemundsson discovered a female ceratioid with two of these smaller fish attached to her belly by their snouts. He assumed it was a mother and her babies, but was puzzled by the arrangement.

“I can form no idea of how, or when, the larvae, or young, become attached to the mother. I cannot believe that the male fastens the egg to the female,” he wrote. “This remains a puzzle for some future researchers to solve.”

When Saemundsson kicked the problem down the road, it was Charles Tate Regan, working at the British Museum of Natural History in 1924, who picked it up. Regan also found a smaller fish attached to a female ceratioid. When he dissected it, he realized it wasn’t a different species or the female angler’s child. It was her mate. 

The “missing” males had been there all along, just unrecognized and misclassified, and Regan and other scientists, like Norwegian zoologist Albert Eide Parr, soon figured out why the male ceratioids looked so different. They don’t need lures or big mouths and teeth because they don’t hunt, and they don’t hunt because they have the females. The ceratioid male, Regan wrote, is “merely an appendage of the female, and entirely dependent on her for nutrition.” In other words, a parasite.

When ceratioid males go looking for love, they follow a species-specific pheromone to a female, who will often aid their search further by flashing her bioluminescent lure. Once the male finds a suitable mate, he bites into her belly and latches on until his body fuses with hers. Their skin joins together, and so do their blood vessels, which allows the male to take all the nutrients he needs from his host/mate’s blood. The two fish essentially become one. 

With his body attached to hers like this, the male doesn't have to trouble himself with things like seeing or swimming or eating like a normal fish. The body parts he doesn’t need anymore—eyes, fins, and some internal organs—atrophy, degenerate and wither away, until he’s little more than a lump of flesh hanging from the female, taking food from her and providing sperm whenever she’s ready to spawn. 

Extreme size differences between the sexes and parasitic mating aren’t found in all anglerfish. Throughout the other suborders, there are males that are free-swimming their whole lives, that can hunt on their own and that only attach to the females temporarily to reproduce before moving along. For deep-sea ceratioids that might only rarely bump into each other in the abyss, though, the weird mating ritual is a necessary adaptation to keep mates close at hand and ensure that there will always be more little anglerfish. And for us, it’s something to both marvel and cringe at, a reminder that the natural world is often as strange as any fiction we can imagine.

Naturalist William Beebe put it nicely in 1938, writing, “But to be driven by impelling odor headlong upon a mate so gigantic, in such immense and forbidding darkness, and willfully eat a hole in her soft side, to feel the gradually increasing transfusion of her blood through one’s veins, to lose everything that marked one as other than a worm, to become a brainless, senseless thing that was a fish—this is sheer fiction, beyond all belief unless we have seen the proof of it.”

Why Do Dogs Lick?

iStock/MichaelSvoboda
iStock/MichaelSvoboda

​One of the more slightly annoying things our dogs do (or most adorable, depending on who you ask) involves their tongue obsessively licking every crevice of every spot possible in pretty much the whole world. From our faces to our furniture to themselves, some dogs are absolutely in love with licking anything and everything. Although it can be cute at first, it quickly gets pretty gross. So why do they do it?

According to ​Vetstreet, your pup's incessant licking is mostly their way of trying to show affection. When we pick up our dogs or give them attention, chances are we kiss or pat their heads, along with petting their fur. Their way to show love back to us is by licking.

However, there are other reasons your dog might be obsessively licking—including as a way to get attention. Licking can be a learned behavior for dogs, as they see that when they lick their owner, they get more attention. The behavior can seem like something humans want which, to an extent, it is.

Licking is also a sensory tool, so if your dog is licking random objects or areas of your home, they're probably just exploring. It's easier to get a feel for their surroundings if they can taste everything. But licking objects like your rug or furniture can also be indicative of anxiety or boredom (which can often lead to destructive behavior), and a recent study linked excessive licking of surfaces to certain gastrointestinal disorders.

Another reason for licking is your dog wanting to clean themselves and/or spots around them. They've seen it since they were born; animals lick things ritualistically for cleaning and care. If your dog seems to be obsessed with licking themselves or one particular thing, they probably are. (Yes, dogs can have OCD, too.)

As Vetstreet points out, "excessive" dog licking often only seems excessive to the dog's owner, not the pooch itself. But if it's bothersome enough to you, a trainer can often help curb your dog's enthusiasm for giving wet, sloppy kisses. And while strange behavior is not rare for pets, if your dog's licking seems odd or in any way concerning, there's no harm in taking your pet to the vet to check it out—even if it's just for peace of mind.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

5 Holiday Foods That Are Dangerous to Pets

iStock/svetikd
iStock/svetikd

One of the best parts of the holiday season is the menu of indulgent food and drinks that comes along with it. But while you enjoy that cup of spiked hot cocoa, you’ve got to be careful your dog or cat doesn’t nab a lick. Here are five holiday treats that are dangerous for your pets, according to Vetstreet.

1. COFFEE

Any coffee lover will agree that there’s nothing quite like an after-dinner cup of joe on a cold night. But pups, kitties, and other pets will have to sit this tradition out. Caffeine can prompt seizures and abnormal heart rhythms in pets, and can sometimes be fatal. Other caffeinated drinks, such as soda or tea, should also be kept away from your four-legged family members.

2. BREAD DOUGH

We know the threat that bread dough poses to the appearance of our thighs, but it’s much more dangerous to our furry little friends. Holiday bakers have to be careful of unbaked bread dough as it can expand in animal stomachs if ingested. In some dogs, the stomach can twist and cut off the blood supply, in which case the pup would need emergency surgery.

3. CHOCOLATE

Cat and dog in Santa hats chowing down on plates of food
iStock/TatyanaGl

A little chocolate never hurt anybody, right? Wrong. The sweet treat can cause seizures and even be fatal to our pets. Darker chocolate, such as the baker’s chocolate we love to put in our holiday cookies, is more toxic to our pets than milk or white chocolate. The toxic ingredients include caffeine and theobromine, a chemical found in the cacao plant.

4. MACADAMIA NUTS

Macadamia nuts, which are a common ingredient in holiday cookies and often put out to munch on as an appetizer, can be toxic to dogs. While poisoning might not always be easy to detect in a pet, clinical warning signs include depression, weakness, vomiting, tremors, joint stiffness, and lack of coordination.

5. ALCOHOL

Think back to when you first started drinking and how much less alcohol it took to get you tipsy, because you likely weighed less than you do now. Well, your pet probably weighs a lot less than you did, even back then, meaning it takes much less alcohol to make them dangerously sick. Keep those wine glasses far out of reach of your pets in order to avoid any issues. Well, maybe not any issue: We can’t promise that this will stop you from getting embarrassingly drunk at a holiday party this year.

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