The mushroom coral is the most unusual coral species here in Hawai‘i. Its Hawaiian name is ‘ako‘ako‘a kohe, which means “vagina coral,” and in old Hawai‘i they were also called razor corals due to their hard, sharp ridges.
This 7-inch-wide, rock hard coral does not attach to the reef like most other corals, so it is classified as a free-living coral. The top of the coral has sharp ridges radiating out from a central mouth on the rounded upper side.
The bottom side is flat, where they sit on the reef. These corals prefer calm water where they do not get tossed around, but if they do get flipped over they can regrow a dome shape out of the flat bottom.
Most stony corals build coral colonies. A single lobe coral may have thousands of small individual coral polyps all stacked on top of each other like an apartment complex for people. The mushroom coral is just one single live coral with a hard calcium carbonate structure, so it is more like a large, single-family home.
The mushroom coral has hair like cilia on its top, which filter feed and bring the food to the central mouth. They also grow algae in the coral tissue that produces sugars through photosynthesis that the coral feeds on. The algae gives ‘ako‘ako‘a kohe its brown color, as the live coral is pure white.
I see these unusual, rare corals from time to time on my scuba dives, usually just one at a time, but sometimes I see two or three together except for one unusual colony on the south side of Kaua‘i.
I was snorkeling one day in Po‘ipu and right out in front of a hotel in only 10 feet deep of water I found a colony of over 1,000 mushroom corals. Why they are all in this one location is still unknown, but it turns out it may be the largest known mushroom coral colony in Hawai‘i.
Years ago, the Hawaiians collected these corals and used them to sand and polish their canoes, using the sharp hard ridges on top of the coral. They also used the coral to scrape the hairs off of pig skin.
You can see ‘ako‘ako‘a kohe in action in my underwater educational marine life series on my website at www.underwater2web.com. I have hundreds of movies that are kid friendly and great for the entire family to watch to learn all about marine life world wide.
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Terry Lilley is a marine biologist living in Hanalei. He is co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawaii go to www.reefguardianshawaii.org.
