Europe’s first ‘cryo-coral babies’ signal the next step in global coral reef restoration efforts 

Wednesday, November 27^th 2024 marked a groundbreaking moment for coral conservation. For the first time ever in Europe, coral eggs were successfully fertilised using frozen and thawed coral sperm. This advancement was the result of a direct partnership between the Horniman Museum and Gardens and the wildlife biobanking charity Nature’s SAFE, highlighting the potential of cryopreservation to enhance coral conservation efforts in the face of climate change. 

The Horniman Museum and Gardens is home to some of the world’s rarest coral species. Dr Jamie Craggs, Principal Aquarium Curator and Living Collections Manager at the Horniman, has spent the past 12 years conducting world-class scientific research to help save endangered corals.

In the ocean, most corals spawn once a year over only a couple of nights, releasing eggs and sperm into the water in response to cues such as the lunar cycle and water temperature. 

Dr Jamie Craggs, Principal Aquarium Curator and Living Collections Manager at the Horniman, says: “For over a decade we have been pioneering approaches to predictably spawn corals in our London facility, and sharing these techniques with the coral reef research community. Our planned reproductive events provide access to eggs and sperm which we use in experiments to better understand corals and how to protect them for future generations.” 

This year, for the annual spawning event, Dr Craggs enlisted the biobanking expertise of Nature’s SAFE in an attempt to cryopreserve coral sperm and indefinitely preserve the genetic material of the corals in their care.

While the Horniman has previously demonstrated the ability to create new coral colonies by fertilising fresh coral eggs and sperm, using cryopreserved sperm allows for greater flexibility by enabling cross-fertilisation between corals that spawn on different days. Typically, coral sperm remains viable for only a few hours after spawning. If successful, this would allow eggs to be fertilised with sperm released days, or even years, prior.

Under the expert guidance of Tullis Matson and Debbie Rolmanis, the team successfully collected and cryopreserved sperm samples from two Australian coral species – Acropora millepora and Acropora kenti – using established protocols and tools by Dr. Mary Hagedorn, a Research Scientist at the Smithsonian Institution who pioneered this technique. The sperm collected was healthy and viable with excellent motility, a crucial element which can determine whether sperm will be able to successfully fertilise an egg. The samples were then carefully frozen, using a specialised cryoprotectant agent to keep the cells alive during freezing. 

Tullis Matson, Founder and Chair of Nature’s SAFE, described the event: “To test that this process had been done successfully, we then defrosted a sperm sample which was frozen the previous day and mixed the solution with freshly collected eggs. Two hours later, the embryos began dividing, confirming that the eggs had been successfully fertilised. This is proof that our biobanking process really works!”

The juvenile corals propagated in November are now 2 months old and growing healthily. These will be kept at the Horniman Museum as part of their land-based corals collection and used for further conservation breeding.

This landmark achievement will be used directly to help conserve coral reefs, which have declined by over 50% worldwide since the 1950s. Dr Jamie Craggs says: “The development of this coral biobank is a significant step in our commitment to conserving coral reefs and builds on the coral spawning work we pioneered in 2012. Over the coming years, we aim to increase the species protected and trial novel preservation techniques to increase the effectiveness of the biobank.”

This milestone also coincides with the formation of the Cryo-CorALS group, a new UK network of organisations dedicated to advancing coral cryopreservation and biobanking, including experts from the Horniman Museum and Gardens, Nature’s SAFE and other leading conservation institutions.

To learn more about the wildlife biobank Nature’s SAFE, visit www.natures-safe.com  

To read more about the Horniman’s innovative Project Coral research, visit: https://www.horniman.ac.uk/project/project-coral/