A rare water beetle has been found during a routine survey of a Bedfordshire town's river.
The largest riffle beetle in the UK, Stenelmis canaliculata, was found by the Environment Agency in the River Ouse in Kempston.
It has been found in only 12 rivers in the past 20 years.
The beetle lives under water and is found in large, deep rivers with gravely bottoms and on exposed stony lake shores.
Drew Constable, from the Environment Agency, said: "This is an important find as the beetle has only a very limited distribution in the UK and is classified as a Red Data Book vulnerable species, which means that it faces a high risk of extinction in the medium-term.
"The beetle needs well-oxygenated water to survive so is an indicator of good water quality."
He said the beetle was found 13 years ago upstream in the River Ouse at Harrold.
"Finding it now at Kempston highlights the importance of maintaining good water quality and habitat within the Ouse river system," he added.