8 Things You Probably Didn't Know About the Seadevil Anglerfish

By now, you've probably seen the awesome footage of a Black Seadevil anglerfish captured by scientists with the Monterey Bay Aquarium Research Institute (if not, you can watch it above). The video, shot at 1900 feet below the surface by a remotely operated vehicle, is believed to be the first footage of a live Seadevil in its natural habitat. Because the creatures live at such great depths, they're rarely seen alive—and, because of that, we don't know a whole lot about them. We asked John Sparks, a curator in the American Museum of Natural History's Department of Ichthyology, to tell us a few things scientists do know about this weird fish.

1. There are six species in the Melanocetidae, or Black Seadevil, family. This one is a female, "probably the Humpback Anglerfish," Sparks says. The fish was first described by Albert Günther, keeper of zoology at the British Museum in London, in 1864. He had obtained it from English naturalist James Yates Johnson, who had gotten the fish from Madeira [PDF]—hence its scientific name, Melanocetus johnsonii.

2. You may have heard how some anglerfish reproduce via the males fusing their bodies to the females' until they essentially become one; the male loses his eyes, fins, teeth, and some internal organs and, from that point forward, lives off of the female, providing sperm when she's ready to spawn. Those fish "are members of the suborder Ceratioidei, [or] deep sea anglerfishes, in which some species are known to reproduce by that means," Sparks says. Still, that's not the norm for those fish—scientists have so far only found parasitic males in 5 of 11 ceratioid families, according to Sparks—and it's probably not what happens when humpback anglerfish mate, either. "That has not been found—yet—in this species," Sparks says. "In the family this species belongs to, only loosely attached, non-parasitic, males have been found on females—they still retain their teeth, etc."

3. The females are much bigger than the males. Typically, Sparks says, this species is "3 to 3 1/2 inches [long]. The largest male known is under 3 centimeters (1.18 inches), whereas the largest female is 18 centimeters (7.08 inches)."

A sketch of the Humpback Anglerfish from the 1896 book Oceanic ichthyology : a treatise on the deep-sea and pelagic fishes of the world, based chiefly upon the collections made by the steamers "Blake," "Albatross," and "Fishhawk" in the northwestern Atlantic. Photo courtesy the Biodiversity Library on Flickr.

4. The tip of the pole-looking thing protruding from the fish's head is called the esca, and its bioluminescence is produced by symbiotic bacteria. This is key in getting the anglerfish fed, because it isn't built for giving chase. "[It's] just swimming slowly, as their body shape—globular—dictates," Sparks says. So in dark environments, the fish uses the glowing esca, which it can move to emulate prey, to attract its own prey, and—in a classic case of the hunter becoming the hunted—chomps down on whatever gets too close...

5. ... with those crazy-looking teeth. "They are sharp and [are] used to impale prey items," Sparks says. "They have large mouths and can eat quite large prey items." Günther, in his description of Melanocetus johnsonii, notes that

The gape is enormous; and although the lower jaw is vertical when the mouth is closed, it can be moved downwards at more than a right angle ... the prey which can be received within the cavity of the mouth actually may exceed the size of the fish itself.

When the specimen was brought to him, Günther said, "the belly was much distended, and contained, rolled up spirally into a ball, a Scopeline fish, which measured 7 1/2 inches in length, and 1 inch in depth."

6. The video mentions the dots on the anglerfish's face, which are organs that allow it to sense movement in the water. These, Sparks says, are called neuromasts, and they're "part of the lateral line system. Agnathans, or jawless fishes, up through amphibians have them. They are for sensing pressure (water movement)—in some species, such as cavefishes, they are quite numerous and well developed."

7. AMNH has the Humpback Anglerfish in its Ichthyology collection. "It's probably the most commonly captured member of Melanocetidae," Sparks says. "It has a wide distribution and is found in all oceans."

8. Though this probably wasn't the anglerfish seen in Finding Nemo—"If I remember correctly the 'species' depicted in Nemo was far more elongate; [it] seemed to me to be an amalgam of different species," Sparks says—the humpback anglerfish is still a star: It once appeared on the cover of Time.

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

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

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Listen to the Impossibly Adorable Sounds of a Baby Sloth
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Sometimes baby sloths seem almost too adorable to be real. But the little muppet-faced treasures don't just look cute—turns out they sound cute, too. We know what you're thinking: How could you have gone your whole life without knowing what these precious creatures sound like? Well, fear not: Just in time for International Sloth Day (today), we have some footage of how the tiny mammals express themselves—and it's a lot of squeaking. (Or maybe that's you squealing?)

The sloths featured in the heart-obliterating video below come from the Sloth Sanctuary of Costa Rica. The institution rescues orphaned sloths, rehabilitates them, and gets them ready to be released back into the wild.

[h/t The Kid Should See This]


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