For the first time in Europe, coral researchers have successfully fertilised coral eggs using frozen and thawed sperm. Spectacular images of the coral spawning are shedding new light on the role cryopreservation is playing in advancing coral restoration efforts.
When corals spawn, they release tiny bundles of eggs and sperm into the water. To become fertilised, each egg bundle must find a sperm bundle from the same species. A team at the Horniman Museum in London recreated this process in tanks in the lab, replicating water temperatures and the rising and setting of both the sun and moon each day to trick the corals into spawning at a specific time. The team worked in collaboration with the UK charity Nature’s SAFE, which has been freezing cells from some of the world’s most endangered creatures to create a genetic biobank.
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Photographs capture the moment Acropora millepora corals spawned in November 2024 at the Horniman, releasing clouds of tiny bundles glimmering against the artificial darkness of the tanks. The team intercepted sperm from this spawning and placed it in a deep freeze using a specialised cryoprotectant agent to keep the cells alive during the freezing process.
To prove the frozen sperm could be used to produce living coral at a later date, the researchers then thawed the sperm and mixed it with freshly collected eggs to create embryos. “Two hours later, the embryos began dividing, confirming that the eggs had been successfully fertilised,” at Nature’s SAFE said in a statement.
Scientists in the US and Australia have managed to , but this is the first time it has been achieved in Europe. The field is developing rapidly – last year, the first corals fertilised using frozen sperm were , on to the Great Barrier Reef in Australia.
Eventually, the team hopes to freeze coral eggs, with the aim of creating a biobank of genetic material that could be used to restore coral reefs should wild corals die out due to climate change. that if warming reaches 2°C above pre-industrial levels almost all coral species around the world will perish. Cryopreservation also supports work to develop hybrid corals, which may spawn at different times but could be more resilient to climate impacts.
