Photographs from Fisheries Exploration and Conservation

We’ve told you about the world’s oldest species of fish, which swims in the waters around parts of Indonesia… but did you know that the country is also home to the world’s smallest fish? No? Neither did we.

Paedocypris progenetica is a species of cyprinid fish found around Sumatra – but you won’t see it if you’re diving with us, though, as it’s endemic to the island’s peat swamps and backwater streams, in water that’s about 300 times more acid than rainwater. This fish is teeny – females reach a maximum of 10.3mm in length while males grow to just 9.8mm.

The fish, which belong to the carp family, are see-through and look a little like larvae. They have a reduced head skeleton, which leaves the brain unprotected by bone. “This is one of the strangest fish that I’ve seen in my whole career’, said Ralf Britz, zoologist at the Natural History Museum, who helped analyse its skeleton and the complex structure of the pelvic fin when it was discovered in 2006.

Blog posts you might enjoy