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IVF, surrogacy to save frogs?

G-Online

Conservation

Tusked frog

Tusked frog (Adelotus sp.), listed as vulnerable, could be saved as a species with IVF, if scientists are successful.

Credit: Ian Morris. Amazing Facts About Australian Frogs and Toads and A Wild Australia Guide Frogs, Steve Parish Publishing.

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A severe decline in frog populations has led researchers to try a novel conservation approach: amphibian IVF.

Researchers at the Institute of Zoology and Amphibian Ark in the UK are creating a biobank of cryogenically frozen sperm and eggs from rare and endangered frog species.

The frozen tissue could be used to impregnate more common frogs, raising the possibility of a frog surrogacy program for those species that brood their eggs internally.

"The biobank has the potential to help save frogs," said Greg Czechura, a naturalist at the Queensland Museum in Brisbane, Australia.

Amphibian populations are in decline worldwide, and the IUCN Red List estimates that 30 per cent are threatened with extinction.

Czechura said that frog populations collapsed suddenly and mysteriously in the late 1970s and early 1980s.

"It was completely unprecedented," he said.

Hardest hit were frogs that should have been the most secure, living in national parks or mountainous reserves.

The main culprit seems to be chytrid fungus, thought to be introduced to Australia in the mid-1970s.

"Most chytrid fungi are benign, but one is a frog-killer," he said.

Climate change may also have been a factor in frog decline, said Czechura, as well as the introduction of invasive weed species. Habitat loss from urban sprawl and salination of freshwater river systems is also putting pressure on frogs.

The biobank was proposed because conservation efforts have been stymied by frogs' reluctance to mate in captivity. Many species require a complex combination of environmental cues to trigger breeding, such as day length, humidity and temperature.

A vial of sperm in the freezer can be a much more economical approach to species preservation, and the biobank may lead to frog IVF procedures instead, researchers said.

"In principle, it is very easy to do," said Rhiannon Lloyd, a reproductive biologist from the Institute of Zoology in London, UK.

Challenges ahead

Because most frogs lay eggs that are fertilised externally by male frogs, the IVF process is much less complex than it is for humans - the sperm and eggs need only be mixed in a petri dish with water.

However, the scientists still have their work cut out for them. "To date, it has been impossible to freeze frog eggs successfully," Lloyd said.

Frog eggs are 10 times the size of a mammalian egg, so they are too big to penetrated by the chemicals that protect them from being destroyed in the freezing process.

Frog sperm, on the other hand, freezes well so researchers in Germany are experimenting with ways to use two sperm cells and an egg from a non-threatened species to make offspring.

Still more challenging is IVF for the few frog species that brood their eggs internally. It may be possible to use surrogate mothers from more common species, but very little is known about the reproductive anatomy and physiology of most amphibians, so this approach could be tricky, Lloyd said.

The biobank follows in the footsteps of the 'doomsday' seed vault in Norway and Frozen Ark in the UK, which preserves DNA and, where possible, sperm and eggs from a wide variety of endangered species.

Amphibian Ark hopes to establish a global network of biobanks just for amphibians - important work, Czechura said. "Once, where you had seven or eight species calling along creeklines, now there's dead silence," he said. "It's a tragedy."