Some fish can walk, but the armored catfish goes one step further in wriggling its way across desert environments in search of resources. Wriggling is the wrong word, however, as scientists considered the mode of locomotion to be so unusual as deserving of its own word: reffling.
The armored catfish reffles its way across land when it finds itself at a dead end in its present habitat. It may be that the isolated body of water it was living in has run out of food or some other resource, and so rather than giving in to its fate, it ups sticks and reffles off someplace else.
These fish are loricariid catfishes, a highly diverse group of fishes that can be found in Central and South America. They have a highly specialized morphology that enables them to inhabit aquatic and terrestrial environments without dying – but that doesn’t mean it's easy.
In National Geographic's Welcome To Earth, we saw an armored catfish making the perilous journey. It leaves a unique track in the sand as it reffles its way towards water. The clip states they can survive for hours at a time on land, but if time runs out, it can be fatal.
Fortunately, the nomadic catfish they caught on camera completes its mission, reffling across the sand and splashing back into more comfortable aquatic surroundings. They're able to navigate thanks to tastebuds that line their bodies and can detect compounds that indicate water's proximity and quality.
The term “reffling” was coined by a 2021 study that sought to better understand the terrestrial behaviors of armored catfish, which were previously poorly described.
“Loricariid catfishes use a novel, highly asymmetric form of axial appendage-based terrestrial locomotion involving their mouth, pectoral fins, pelvic fins, posterior axial body, and tail,” wrote the authors. “As this behavior is so unlike any other described locomotor behavior, we have created a new word to describe it: reffling.”
The unique approach to moving across land may be the consequence of them being rather stiff for a fish, but their rigidity has its perks, too.
“These species have numerous unique morphological traits that may greatly reduce body and fin flexibility,” they continued. “Because loricariids are so inflexible, they may be constrained into reffling as their only means of terrestrial locomotion, but their stiffness may improve force transmission, allowing them to be among the fastest fishes on land.”
Those fins weren’t made for walking, and that’s not what armored catfish do.