A species
Staghorn coral
Acropora cervicornis
Tiny animals farming algae in golden antlers
You and the staghorn coral last shared an ancestor about 700 million years ago (on 1 November, if life's history were one year).
It looks like golden antlers, but staghorn coral is an animal — a surprise relative of the moon jellyfish shown beside it on the tree. What looks like a single branching coral is really a colony of hundreds to thousands of tiny animals called polyps. Each one builds a hard limestone cup joined to its neighbours, and farms tiny algae inside its body for food.
The golden-brown colour comes from the algae, not the coral itself. The animals themselves are almost clear. Colonies grow to about a metre high and two metres across — about as wide as a sofa — with the longest branches longer than a person is tall. Many colonies join into dense fields called thickets that build reefs and shelter fish.
It lives in clear, shallow, sunlit water about five to eighteen metres deep around Florida, the Bahamas and the Caribbean. It needs warm water, strong light and a hard surface for its young to settle on. At night each tiny animal pushes out stinging tentacles to catch tiny drifting sea life.
White tips mean new growth
The white tips on brown branches are new growth where the branch is getting longer.
Broken bits can regrow
If a branch snaps off, the piece can reattach to the reef and grow into a new colony with the same genes.
One big spawning night
Once a year after the late-summer full moon, colonies release eggs and sperm into the water together.