" and then she pulled out my mushroom tip!": Fungia corals

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Oval mushroom corals are solitary individuals that do not form colonies like most other corals in Hawaii. They can be tumbled about in ocean currents and even flip themselves over when necessary to ensure that their mouths remain on the topside.

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Ka Mo"˜olelo Moana: Local waters offer array of mushroom corals
April 3, 2011
By PAM DAOUST , for The Maui News
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Mushroom corals are so named because of their mushroomlike appearance. An oval mushroom coral has a central slit, or mouth opening, surrounded by ridges radiating outward like the gills on the underside of a mushroom cap.

Except for its size, which can be as large as 8 inches in diameter and a half-inch thick, this species looks like it's ready to be stuffed with something tasty and served as an hors d'oeuvre. However, its texture differs from that of an actual mushroom.

The ridges of the oval mushroom coral are sharp. Known as septa, the ridges have small bumps, or retracted tentacles, used for extracting nutrients from the water column. Hairlike cilia transfer food particles to the mouth and move unwanted detritus to the edges of the creature's oval, disclike shape, where it is discarded. Zooanthellae, or algae cells, living inside the coral provide additional nutrients.

The oval mushroom coral's tentacles may be greenish in color and its mouth purplish. Radiating rows, called costae, of tiny spines stud the coral's underside. The sharp spines and septa give this coral its other common name: razor coral.

Oval mushroom corals are solitary individuals that do not form colonies like most other corals in Hawaii. Mature specimens are free-living, or detached from the reef. They can be tumbled about in ocean currents and even flip themselves over when necessary to ensure that their mouths remain on the topside.

Only when young are mushroom corals attached to the reef by means of a limestone "pedestal." Eventually, this breaks, and new corals evolve from the remnants of the pedestal, resulting in an ongoing process similar to "budding." Many juveniles will form from a single pedestal.

Mushroom coral adults also reproduce by spawning and releasing either eggs or sperm. Spawning in Hawaii for this species is known to occur from July through September between the hours of 5 and 7 p.m., two to six days after a full moon.

In the resulting larval stage, an individual is known as a "planula." Planulae drift on currents for a time before settling on the reef and forming polyps that begin the cycle anew.

Other types of mushroom corals found in local waters include the granulated and Vaughan's mushroom corals, both of which are round rather than oval in shape, and prefer deeper waters than the oval mushroom coral. The oval is found most often in areas of moderate to light surge at depths no greater than 26 feet, while the granulated occurs at depths of 50 feet or more and the Vaughan's at 40 feet or more.

Two species of mushroom corals have a distinct flower, or blossomlike, appearance. Fragile mushroom corals and distorted mushroom corals both have "petals" branching out from centrally located mouths. In each, the "petals," or sections, are small - no more than an inch in diameter. These can break off from the whole and shatter into smaller pieces. Each piece can evolve then into an entirely new individual.

Hawaiians of old found good use for the hard, stony skeletons of various types of mushroom corals. The skeletons were used to remove bristles from pigskins or as abrasives for polishing canoes and other woodwork. The Hawaiian term used to describe mushroom corals is 'ako'ako'a kohe, and the scientific term is Fungia scutaria.

* Pam Daoust is an author and marine educator at Maui Ocean Center. "Ka Mo'olelo Moana," or "The Ocean Story," is a monthly column submitted by the Maui Ocean Center, which is open from 9 a.m. to 5 p.m. daily in Maalaea. For more information, call 270-7000.

© Copyright 2011 for The Maui News. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
 
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