The Earth’s deepest river is the perfect lab to study the phenomenon known as convergent evolution, a process where unrelated or distantly related organisms independently evolve similar traits, according to scientists who studied the Congo River and presented their bizarre findings in January at the American Geophysical Union, reports The New York Times.
The Congo Project, a partnership between the University of Marien Ngouabi in the Republic of Congo, University of Kinshasa, in the D.R.C., and the A.M.N.H., in 2008 and 2009 sent white water kayakers whose kayaks were equipped with echo-sounders and depth measurement equipment to run the rapids during the low-water season after the group found a strange fish.
“In one place, we found this particularly weird fish,” Dr. Melanie Stiassny, an ichthyologist with the American Museum of Natural History in New York, told the news outlet.
“It’s a blind, depigmented cichlid — it looks very much like a cave fish, but there are no caves in the river.”
Stiassny and the team wondered why they hadn’t seen a fish like it until “bubbles formed under its skin and gills,” a sure sign of decompression syndrome, said Stiassny.
So the team set out to find out if there could be deep water in the lower Congo.
The data showed a tough underwater landscape containing “huge towers of rock, stripped bare of sediments and plants by fast currents that run both upstream and downstream,” per the Times.
“Almost as if you’ve got two rivers in the same channel,” Dr. Melanie Stiassny, an ichthyologist with the American Museum of Natural History in New York, told the Times.
The impassible river barriers isolate fish populations and have resulted in the emergence of hundreds of new species.