These branching structures belong to an animal, not a plant. Elkhorn coral grows in shallow Caribbean waters; thickets shelter fish and other creatures.
Flattened branches spread from a central trunk. Colonies are golden tan to pale brown and consist of many small polyps.
At spawning, Acropora palmata releases small bundles containing both eggs and sperm. A colony produces both types of reproductive cells and releases them into the sea.
In 2018, researchers combined fresh eggs collected in Curaçao with thawed sperm from other regions. The sperm had been collected in Florida two years earlier and Puerto Rico ten years earlier and stored in liquid nitrogen. These crosses produced offspring from geographically separated donor colonies.
The larvae were transported to two facilities in Florida and reared after settlement. Young colonies remained alive at six months. Genetic analysis of a subset produced with Florida sperm also confirmed parentage from the two regions. The experiment enabled breeding across regions by transporting preserved cells rather than large adult colonies.
An extinction-risk assessment has not been added yet.
Warmer seawater is one threat. Bleaching can remove internal algae, leaving coral vulnerable to starvation, disease and sometimes death.
Restoration projects grow coral, plant it at sea and monitor survival and growth.
The 2021 study demonstrated that cryopreserved sperm can produce offspring from colonies originating in different regions. The authors propose the method as a tool to preserve remaining genetic diversity and use it in breeding. Survival after outplanting and tolerance of stresses such as heat remain questions for further investigation.