This fish didn't get the memo. While its fellow aquatic friends swim through the water, this creature's evolved skeletal features that allow it to walk like a salamander, clambering over slick rocks as waterfalls crash down on top of it.
This cave-dwelling fish -- Cryptotora thamicola is its proper name -- lives in the waters of Thailand. But the conditions it thrives in would put off most fish, as it subsists on a diet of microbes that live on the vertical walls of its underground caverns. While that would make grabbing a meal hard for most fish, this one simply... walks up the walls to eat.
Researchers have now studied the two-inch long fish in detail and have come to some fairly extraordinary conclusions. While most fish have simple pelvic bones to control their fins, CT scans reveal that the Cryptotora thamicola actually has a developed pelvis which resembles that of a tetrapod, like a cow or horse. It also has vertebrae that overlap, which allows it to stiffen its spine while it takes a step.
These quirks mean the fish is able to walk with a gait that, according to the researchers, resembles a salamander. In the gif at the top of the page you're actually seeing the fish walk up a wall that's inclined at almost 90 degrees. Ninety degrees! The research is published in Scientific Reports.
The finding may help researchers understand how life evolved the ability to crawl out of the sea an wind up living on land. It could, perhaps, possibly be that a fish like this was the start of that shift.