Ananova:

Scientists have discovered the world's smallest fish in a tropical acidic swamp.

Females grow no bigger than 7.9mm (0.31in) and the male measures up to 10.3mm.

That makes it the smallest known vertebrate - an animal with a backbone, reports the Independent.

Biologists found the fish in forest swamps on Sumatra, where the peat water is 100 times more acidic than rainwater.

Scientists had thought little could survive in such peat swamps but were astonished to discover several species of small fish including the latest specimen, named Paedocypris progenetica.

Swiss biologist Maurice Kottelat and Tan Heok Hui, from the Raffles Museum of Biodiversity Research in Singapore, discovered the fish by sieving the water with a fine-mesh net.

They sent specimens of the fish to the Natural History Museum in London where Ralf Britz, a zoologist and fish expert, identified it as a species new to science.

Dr Britz said: "This is one of the strangest fish that I've seen in my whole career. It's tiny, it lives in acid and it has these bizarre grasping fins."

One theory is that the fins are used by males to grasp females during mating. Another is that they are used to capture eggs as they are released by females into the murky swamp.