Mature females of the Paedocypris progenetica, a member of the carp family, only grow to 0.31 inches and the males have enlarged pelvic fins and exceptionally large muscles that may be used to grasp the females during copulation, researchers wrote in the Proceedings of the Royal Society, published Wednesday by the Royal Society in London.
"This is one of the strangest fish that I've seen in my whole career,' said Ralf Britz, zoologist at the Natural History Museum in London, who helped analyze the fish's skeleton. "It's tiny, it lives in acid and it has these bizarre grasping fins. I hope we'll have time to find out more about them before their habitat disappears completely."
The previous record for small size, according to the Natural History Museum in London, was held by an 8-millimeter species of Indo-Pacific goby.
The new fish was discovered on Sumatra island by fish experts Maurice Kottelat from Switzerland and Tan Heok Hui from the Raffles Museum of Biodiversity Research in Singapore. They were working with colleagues from Indonesia and with Kai-Erik Witte from the Max Planck Institute in Germany.
According to the researchers, the fish live in dark, tea-colored water with an acidity of ph 3, at least 100 times more acidic than rainwater. Swamps like this were once thought to harbor very few animals, but recent research has revealed that they are highly diverse and home to many species that occur nowhere else.
Peat swamps are under threat in Indonesia from fires lit by plantation owners and farmers as well as unchecked development and farming. Several populations of Paedocypris have already been lost, researchers say, according to the Natural History Museum.