The images show the tiny three-year-old freshwater pearl mussels, which would only otherwise be seen using a microscope
A breeding programme to save the endangered freshwater pearl mussel from extinction has captured images of the young shellfish thriving.
Environment Agency Wales is breeding the species - one of Europe's rarest - in a hatchery in Mawddach, Gwynedd.
New images show three-year-old mussels the size of pinheads, which could only otherwise be seen using a microscope.
They will now have to wait another three to five year to be considered 'grown up' enough to enter the wild.
The breeding programme mirrors what should happen in the wild, using salmon and trout as 'host fish' for the mussels. In recent years, this has not been happening successfully in Welsh rivers.
From a batch of 70,000 original mussels reared in 2005 at the hatchery, only 100 have survived to reach the milestone of three-years-old. This closely matches the survival rate of the young pearl mussels in the wild.
The pictures show what the young pearl mussels look like in their formative years. With a lifespan of over 100 years they will not reach full adulthood until 10 to 15 years of age.
Poor river quality and pearl fishing put the freshwater pearl mussels at risk
Huw Jones, who leads the pearl mussel programme for Environment Agency Wales, said they were "really pleased" to see the young mussels developing.
"Their breeding cycle is such a complex one that it hasn't been easy," he said.
"But we are starting to see results."
In the past, a variety of problems have led to the mussels' decline, with the most impact being caused by poor water quality, silt build up, habitat loss and, pearl fishing.
Mr Jones said that water quality and habitat in rivers has improved in recent years but the Environment Agency still wanted to do more to ensure the mussels would adapt successfully to the wild when they are released.
"The mussels need good, clean rivers and a suitable habitat for them to thrive when we return them to their natural environment," he said.
"We are working with key people on plans to identify ways to improve the water quality and ecology of Welsh rivers for people and for wildlife like the native freshwater pearl mussel."
The agency is also continuing to breed new batches of the mussels at its hatchery each year and is working to improve their survival rates.
In total, pearl mussels have been historically reported from 23 Welsh rivers, but comprehensive surveys in the 1990s found populations surviving in only 11 of them.