Staghorn coral (Acropora cervicornis) is found throughout the Caribbean. It forms an important part of the Florida Keys Reef Tract, which is the third largest living coral reef in the world and the only one in North America.
Coral reefs are under threat from ocean warming and acidification, which can result in coral bleaching and increased susceptibility to disease threats. There are several strategies for the conservation of coral reefs including banking coral sperm to preserve valuable genetic material that one day might be re-introduced to the reef, bringing new genes to the population. SEZARC is working with the Coral Restoration Foundation in Key Largo, USA to collect and freeze sperm from genetically diverse staghorn coral genotypes as part of a national effort to preserve genetic material from corals from the Florida Reef Tract.
Once a year, about three days after the full moon in August, the coral spawn, releasing gamete bundles that can be collected. After bundle breakdown, the sperm are separated, concentrated and frozen over liquid nitrogen before storing in a liquid nitrogen dewar. Once frozen, they can be preserved for hundreds of years or until the genetic material is needed back into the coral population.
SEZARC is investigating the optimal time for coral sperm cryopreservation after spawning. In vitro fertilization studies have revealed declines in sperm quality over the course of the night, once the bundles have released the sperm and the eggs, and recent transmission electron microscopy studies have demonstrated sperm intracellular changes that start to occur soon after spawning. This suggests a narrow window exists for optimal fertilization, so sperm cryopreservation before the sperm become too aged is critical. L Penfold, J Wyffels, K O’Neill, A Moura. (2022). Reproduction, Fertility and Development 34(2) 234 – 324.