The last living colony of a rare species of tree snail has been entrusted to a British zoo in the hope of reviving its fortunes.
The centimetre-long tree snails, known as Partula Faba, are endemic to the French Polynesian island of Raiatea, but are now extinct in the wild.
Bristol Zoo Gardens is hoping to save the species, threatened by "cannibal snails" and invasive plants in its native land.
Invertebrate experts are nurturing the colony of 88 snails in a custom-built, climate controlled room in the Zoo's Bug World - the only place in the world where these snails can now be found.
The group have now produced 15 offspring, the smallest two mm long - described as a "significant boost" in the struggle to save the species. The zoo took the last delivery of snails in February this year.
Keeper Grier Ewins said: "Tree snails are incredibly endangered, with Partula faba being one of the most endangered of them all - they really are on the edge of survival.
"The great news, however, is that this last remaining population of Raiatean tree snails has been steadily growing since we took them on."
She added: "Working with these, and so many other rare animals at the Zoo, is incredibly satisfying.
"To think that I am nurturing the entire global population of these snails, and encouraging them to breed, is very rewarding - as well as a huge responsibility.
"It shows just how important the role of zoos and other conservation organisations are in helping to breed and protect endangered species, otherwise we risk losing many species forever, which would be a tragedy for us and future generations of people."
The French Polynesian tree variety has been decimated by invasive snails which were introduced to the islands in the 1970s.
Between the mid 1970s and mid 1990s an estimated 80 per cent of tree snail species were lost.
Loss of habitat, due to aggressively spreading plants such as the South American velvet tree, is also changing the landscape of the islands and affecting wildlife.
Five species of Polynesian tree snail are being kept at Bristol Zoo, all of which are part of an international captive breeding programme.
Bristol Zoo's Curator of Invertebrates, Warren Spencer, said: "Although Raiatean tree snails are extinct in the wild, Bristol Zoo hopes to work with its conservation partners to release some snails into safe 'zones' - reserves - back on the island of Raiatea and then to the surrounding area of a new reserve.
"However, this can only be done once we have successfully removed or controlled the spread of the predatory 'cannibal snail', which was responsible for this species' extinction."
Currently 20 Partula species have been saved from extinction by Zoos and Universities. Fifteen are classified as extinct in the wild and five are critically endangered.
Bristol Zoo also breeds other animal species which are extinct in the wild, such as the Socorro dove, Butterfly splitfin fish, Golden sawfin fish and Potosi pupfish - which was successfully bred last year.
Other critically endangered animals which Bristol Zoo breeds include western lowland gorilla, Indochinese box turtle, Annam leaf turtle and Egyptian tortoise, as well as numerous mammal, bird, fish, invertebrate and amphibian species.