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There are fascinating fish to be found in almost every environment on earth, from flying fish, walking fish and humming fish to electric fish, shrinking fish and even hibernating fish. But despite the wondrous variety already on display, Mother Nature can still find a way to surprise us with a species that’s almost beyond belief, such as the Waterfall-Climbing Cave Fish!
 
Also known as the Cave Angelfish, Cryptotora thamicola is one of the rarest and most elusive fish in the world. Reaching a length of only 1.1 inches, this tiny species of hillstream loach may easily be the world's most cave-adapted fish and has only been found in eight sites within Thailand's Pang Mapha limestone cave formation.
 
Like many other cave-dwelling species, this freshwater fish has adapted to its pitch-black surroundings by becoming both eyeless and pigment-less, but it also has specially-evolved pectoral fins with microscopic hooks that allow it to scramble vertically up waterfalls and cling nimbly up through the fast-moving waters. Although not truly lobed like the fins of lungfish or coelacanths, C. thamicola’s fins are indeed able to move like feet, giving it a secure purchase on the treacherously slippery wet rocks and a whole new dimension of movement.
 
Being so highly specialised means that the fish fill a specific niche in their subterranean ecosystem with little competition for the algae and biofilm that they feed on, but as a result, they are also extremely sensitive to water changes and disturbances within their environment.