It's not hard to see why this image of what looks like a clam-fish-squig hybrid has been shared thousands of times on social media – and keeps resurfacing. But as is the case with most close encounters of the weird kind, there is a perfectly logical explanation for this creature's "alien" appearance.

Image: Leandra Vissr/Facebook

The first time this red beastie pinged on our radar was in 2014, when vacationer Leandra Vissr happened upon its carcass on a beach near Cape Town, South Africa. Perplexed by her find, she took to Facebook for some answers. Though many commenters at the time questioned the authenticity of the image, what you're looking at is a real animal: a clingfish known as the red rocksucker (Chorisochismus dentex).

Alive, rocksuckers are actually rather cute, with that fearsome dentition hidden behind a pair of fleshy lips. But as is the case with almost every animal (humans included), the sun has a way of turning a supple exterior into lobster leather. 

Native to African waters, red rocksuckers are commonly found in tide pools (rock pools) from the Namibian coastline and on towards the northern reaches of South Africa's KwaZulu-Natal. When they wash up dead, the blazing sun affects their scales first. As they dehydrate, the "skin" begins to shrink. This desiccation continues until, eventually, the lips move back far enough to expose the jaws that once fit comfortably within them. 

Essentially, the fish mummifies from the outside in. This:

Image: Wikimedia Commons

Becomes this:

Image: Another specimen was found in Cape Town some 6 months after Vissr's find. Image: Melinda Ridgard/Fishbase (Creative Commons)

The fish feed primarily on limpets  aquatic snails that use a powerful muscular "foot" to cling to rocks and their impressive chompers are the perfect tools for prying the molluscs loose. 

"It's a most fascinating specialised fish," ichthyologist Robin E. Stobbs, who worked to document the feeding behaviour of these animals using x-ray technology, told us via email.  

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A red rocksucker makes quick work of a limpet. Image: Robin E. Stobbs

Limpets are so strong that you'd find it tough to pull one off a rock if you tried. The key is stopping them from creating suction in the first place, a feat that the rocksuckers accomplish in a matter of seconds, Stobbs explains. 

"After a clingfish has discovered a limpet about to move, it positions itself facing the mollusc," he says. "After watching the limpet for a few seconds, the clingfish leaps forward and upward, dives onto the shell with mouth opened, inserts its upper teeth under the shell and with the forward momentum resulting from the leap, levers the limpet off the substrate and swallows it immediately." 

And those built-in crowbars don't stop at sea snails. During a 1980 study, Stobbs found that some 12 percent of the rocksuckers' diet was made up of spiny urchins. 

X-ray images show an urchin (left) and limpet (right) inside the digestive system of a rocksucker. Images: Robin E. Stobbs (used with permission)

As you can imagine, hard parts like shells and urchin exoskeletons (known as tests) are hard to digest, so the fish eliminates them  whole  encased in mucous capsules.

So there you have it, folks. We might not be dealing with an alien mutant, but this shell-pooping, tooth-baring fish is just one more example of the incredible life that lurks beneath the waves. 

If that's not enough desiccated rocksucker for you, this image is sure to do the trick.


Top header image: Leandra Vissr/Facebook