When New Zealand local James Beuvink and his girlfriend spotted a black, blob-like fish "walking" along the sea floor, they weren't sure what they'd found. Curious to learn more, they scooped up the strange animal, hoping nearby fishermen could shed some light on its identity. Much to their surprise, no one had ever seen anything like it. The specimen was sent to the Museum of New Zealand Te Papa Tongarewa, where scientists are working to unravel the mystery. 

A closer look revealed the sea creature to be a striped, or striated, frogfish (Antennarius striatus), but its inky colouration has fish collections manager Andrew Stewart scratching his head. "This is the first time I've seen one jet black, with no body markings at all," he says. Only a trace of pattern remains on the fish's illicium (the stem of its lure).

It's possible that the animal could be a cryptic subspecies, but the more likely explanation is that Beuvink discovered a rare colour morph – much like the kind you'd see in snakes and other reptiles. In fact, ichthyologist David Snyder managed to photograph a similarly coloured striped frogfish off the Florida coast several years ago, but this is the first one to turn up in New Zealand waters.

"No one is quite certain whether this black morph (along with other colour variants) is genetically distinct enough to be a separate species or subspecies, as we tend to find them one by one and would need a larger sample size," the Te Papa museum explained on Facebook. "It's a pretty neat animal though!"

Those fleshy "legs" you see are the perfect appendages for the fish's seafloor-cruising lifestyle. Frogfish are stealth hunters, and rest on the thick fins while they wait patiently for their prey. The family and genus names are derived from the Latin "antenna, antemna" meaning "appendage on the head" – a nod to the fish's worm-like lure, known as an esca. 

While these animals feed mostly on crustaceans and other bottom-dwelling fishes like flounders and shrimp gobies, marine biologists have observed them snacking on invasive lionfish in recent years (which is a bonus for ecosystems in some parts of the world). 

"Frogfish have the fastest bite of any vertebrate, with mouths that can expand at speeds rivalling those of a bullet leaving the barrel of .22 calibre rifle," Te Papa museum staff added. "And that's in water (which is 800 times denser than air!)."  

For those who are wondering, the animal would have been transferred to Auckland's Kelly Tarlton's Aquarium, had it not died en route. 

Tissue samples of the New Zealand fish will be analysed over the coming months, and the team hopes to uncover clues about its genetic origin. It will remain in the museum collections for years to come, where scientists from around the world can access it for study.

If this fish's stunning good looks aren't quite enough for you, check out this beauty:

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