Coral Made from Frozen Sperm in Australia

Our fourth year of field work at the Australian Institute of Marine Science (AIMS) is winding down. The season was long this year with a split spawn, meaning that the 1st full moon of the Australian summer was very early in November, so the lunar signal that the coral use to time their normally once-yearly spawn was not really clear, so some coral spawned with that 1st full moon and some spawned with the second full moon of the summer in early December. We took a full crew including Dr. Mary Hagedorn, head of Reef Recovery as well as her assistant Ginnie Carter, aquarist Mike Henley and Taronga Conservation Society’s reproductive biologist Rebecca Hobbs for the November spawning event. During that time, we were able to a new species to our frozen bank at Taronga’s Western Plains zoo as well as increase the samples and genetic diversity of 4 other species, bringing our count for Australian species to 7 and our species count worldwide to 11.

Sperm samples being frozen. Photo by V. Carter.

Moving forward from banking material, this year, we made coral larvae from fresh eggs with sperm samples that had been previously frozen, proving the concept of the future uses of our frozen banks. Mike Henley stayed at AIMS through the beginning of December to care for the coral larvae we created as they settled onto tiles in tanks at AIMS. This is a critical period of the coral life cycle in which the coral larvae has to go from swimming about to finding a good place to start laying down their skeleton and growing into what most people think of when they think of a coral, basically, this is the time when they find their permanent home and start to grow. With Mike staying to care for our larvae, he also had the chance to add to their numbers by being at AIMS for the second spawn of the split spawn and creating even more coral larvae from fresh eggs and frozen sperm. Mike will remain at AIMS until December 21st, and then it is our hope that working with AIMS scientists, we can grow some of these coral to maturity.

Mike Henley examining tiles to count settled coral. Photo by R. Hobbs.

Settled juvenile coral that was created using frozen sperm. Photo by M. Henley.

In addition, Rebecca Hobbs worked to create coral embryos from single coral cells. By breaking embryos apart at either the 4 or 8 cell stage of development, each cell that was created is theoretically able to grown into all the cells of a coral, i.e. they are stem cells. Rebecca was able to do this, and from her single cells, she had coral larvae grown, survive and settle. This is important for our work as well, since freezing single coral cells would allow coral to be grown from these cells in the future without the added step of fertilization and need for fresh eggs.

A settled coral grown from a single cell created at the 4-cell stage of embryo development. Photo by M. Henley.

All in all, our fourth year of work in Australia for the Great Barrier Reef spawning event was a great success. We are so happy to add another species to our bank and increase it’s robustness with our other species. We are also so pleased to see our bank working with our settled larvae this year.

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