What is a mushroom coral? Though considered to be 'reef-building' corals, mushroom corals are free living or unattached during their adult lives. There are at least eight species of mushroom coral (Fungia) in Western Australian marine parks, together with at least eight other members of the Family Fungiidae, from five genera (Cycloseris, Herpolitha, Polyphyllia, Sandalolitha and Podabacia).

What do they look like? All mushroom corals bear wide, slit-like mouths and extend short tapered tentacles at night. They are usually brown in colour. Adults are flat or dome-shaped and either circular or oval-shaped. They may have a central arch. The young resemble a mushroom. It can be quite difficult to tell one species from another and from some other family members. Experts identify them from their skeletons. The largest species found at the Rowley Shoals Marine Park (Fungia repanda) can reach up to 30 centimetres in diameter.

Photo: Mushroom Coral

Where do they live? Mushroom corals are most common on the slopes fringing reefs, where they are not subject to strong wave action. Here, a number of species may be found together. Fungia scutaria, however, can be found wedged into crevices on exposed upper reef slopes. Mushroom corals are confined to tropical or subtropical areas. In Western Australia some species can be seen as far south as Ningaloo Marine Park.

What do they eat and how? Corals capture tiny animals (plankton) from the water with their tentacles. They also harvest sugars and oils manufactured by plants known as zoothanthellae that live within their tissue.

Behaviour: These corals usually live as individuals and, remarkably, they are at least partially mobile. Most can move sideways or extract themselves from sand when buried.

Breeding: Mushroom corals generally have separate sexes, but they can reproduce either sexually or asexually. Many species are able to generate 'daughter' polyps on their surfaces if they become partially buried or damaged. Once a year, however, males will release sperm and female polyps release egg bundles, which will become fertilised on the water surface. The resultant planula larvae will attach itself to a solid surface, before developing into a vase-shaped polyp. After it develops a mushroom-like upper surface, the 'stalk' degenerates and the coral becomes detached from it, hence forming a new, free-living individual.

Conservation status: The world’s coral reefs are under threat. Coral bleaching caused by climate change has already caused widespread death of corals and huge areas of reefs around the world are under threat. Even Western Australia’s fairly healthy coral reefs are threatened. As climate change is caused by increased carbon emissions into the atmosphere you can help by doing simple things such as switching off lights and riding your bike to school.

Protecting mushroom corals: Mushroom corals are used by some people to decorate their homes. However, a conservation-minded person would never buy a mushroom coral skeleton from a shop, as it could have been taken alive from the water.