Posted on March 6, 2015, 11:57 am
Researchers have found one of the smallest known fish on record in the peat swamps of the Indonesian island of Sumatra.
Individuals of the Paedocyprisgenus can be just 7.9mm long at maturity, scientists write in a journal published by the UK's Royal Society.
But they warn long-term prospects for the fish are poor, because of rapid destruction of Indonesian peat swamps.
The fish have to survive in pools of acid water in a tropical forest swamp.
"This is one of the strangest fish that I've seen in my whole career," said Ralf Britz, a zoologist at the Natural History Museum in London, UK.
"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 new fish was discovered by Maurice Kottelat (from Switzerland) and Tan Heok Hui from the Raffles Museum of Biodiversity Research in Singapore, while working with colleagues from Indonesia and with Kai-Erik Witte from the Max Planck Institute in Germany.
Ralf Britz helped analyse the animal's skeleton and the complex structure of the pelvic fin.
World's smallest vertebrate, the female Paedocypris fish is 7.9mm long. © Raffles Museum
Paedocypris can sustain their small bodies grazing on plankton near the bottom of their water pools.
To keep their size down, the fish have abandoned many of the attributes of adulthood - a characteristic hinted at in their name.
Their brain, for example, lacks bony protection and the females have room to carry just a few eggs.
The males have a little clasp underneath that might help them fertilize eggs individually.
Being so small, the fish can live through even extreme drought, by seeking refuge in the last puddles of the swamp; but they are now threatened by humans.
Widespread forest destruction, drainage of the peat swamps for palm oil plantations and persistent fires are destroying their habitat.
Science may have discovered Paedocypris just in time - but many of their miniature relatives may already have been wiped out.
There have been claims for even smaller fish but some researchers dispute whether the specimens measured were truly adult forms.
The tiny, see-through Paedocypris fish have the appearance of larvae and have a reduced head skeleton, which leaves the brain unprotected by bone.
They live in dark tea-coloured waters with an acidity of pH3, which is at least 100 times more acidic than rainwater.Threatened swamps
The swamps were once thought to harbour very few animals, but recent research has revealed that they are highly diverse and home to many species that occur nowhere else.
In 1997 the peat swamps were damaged by large forest fires and they are still threatened by logging, urbanisation and agriculture. Several populations of Paedocypris have already been lost.
World's smallest vertebrate is a member of the carp family of fish. © Maurice Kottelat, Cornol /Raffles Museum
The new fish was discovered by fish experts Maurice Kottelat (from Switzerland) and Tan Heok Hui from the Raffles Museum of Biodiversity Research in Singapore. They were working with their colleagues from Indonesia and with Kai-Erik Witte from the Max Planck Institute in Germany. Ralf Britz, at the Natural History Museum , helped analyse its skeleton and the complex structure of the pelvic fin.Previous smallest
The previous record for smallest vertebrate was held by an 8mm species of Indo Pacific goby. The UK's smallest fish is the marine Guillet's goby, Lebetus guilleti, reaching 24mm in length.
Unusual pelvic fin of Paedocypris . © Raffles Museum