Because of their docile nature and tendency to wait around for human scraps near fishing docks, nurse sharks are often dubbed the "puppy dogs" of the shark world. But this oddball specimen, seen recently off the Turks and Caicos islands of the Caribbean, has taken the nickname to a whole new level with dalmatian-style spots. 
Image: Nate Madden/YouTube
The strange-looking morph is caused by leucism, a genetic condition that results in a partial lack of the pigment melanin. The mutation is also known as "pied", "piebald" or "partial albinism" – and we've seen it in sharks before.

What's interesting, however, is that while many leucistic sharks sport either "cow-like" patterns (with large, dark patches) or overall white colouration (seen here in a baby great white and here in a deep-sea swell shark), leucistic nurse sharks tend to be heavily spotted.
"We have only been able to find one other documented case of a leucistic nurse shark online," says Nate Madden, who encountered the fish during a recent dive. "So this is a very rare find!"
The animal's scientific name, Ginglymostoma cirratum (which sounds like it should be chanted to ward off a Dementor), loosely translates to "curly, hinged mouth". Nurse sharks are bottom dwellers, and that namesake feature helps them suck up shellfish, squid and other invertebrates from the sediment.  

Unlike many of their top-predator kin, who need to keep swimming to get oxygen, nurse sharks can safely settle down, and they tend to spend their days resting on sandy bottoms, or in crevices between rocks and corals. Rather than using forward motion to "ram" oxygenated water over the gills (a technique known as ram-ventilation), these long-tailed fish breathe by pumping water with their cheek, or "buccal", muscles.

But don't let that mellow vibe fool you: while nurse sharks are relatively harmless, they still pack hundreds of tiny teeth and will bite if harassed. Oh, and when they bite, they don't let go easily. We saw this first-hand early last year, when a group of bathers in Florida grabbed a baby nurse shark by the tail and reportedly lifted it out of the water.

We're happy to see that Madden and his diving buddies kept their hands off during their recent encounter with the Rorschach wonder. "Hopefully this incredible shark will stay in the Turks and Caicos Islands waters," Madden says.


Top header image: Nate Madden/YouTube screengrab