A giant mushroom coral of some sort.

My friend found a giant mushroom coral of some sort along the coast of Snake Island in the middle of Palawan Island in the Philippines. This giant mushroom coral is unlike any of those mushroom corals I have seen when I scuba dive in many parts of the island. I have no idea what it is.

Searching the internet once again suggested that this giant mushroom coral could be Heliofungia actiniformis or the anemone coral. It can be mistaken as a sea anemone because its tentacles remain during the day. Indeed, it has long tentacles as shown in the photo below.

The anemone coral underwater.

Mushroom corals like this one are solitary and free living, meaning, they are not attached to the bottom of the sea on a hard substrate except when they are at the juvenile stage. Mushroom corals are flat with large centrally-located mouths.

The giant mushroom coral of the species Heliofungia actiniformis above is colored brown to greenish-brown with its long tentacles tipped in white. It was daytime when this picture was taken so it does not exhibit the behavior of other corals which extend their tentacles exclusively at night to trap their prey. Juveniles of this species look like flattened discs with a stalk attached to hard substrate.

The giant Heliofungia actiniformis used to be classified under the genus Fungia but later examination revealed a different polyp structure so they were reclassified to belong to a genus of its own, i.e. Heliofungia derived from the Greek word “helio” meaning sun and “fungus”, meaning mushroom.

Heliofungia actiniformis is also called Long Tentacle Plate Coral, Heliofungia Plate, Sunflower Mushroom Hard Coral or Disk Coral. It can grow up to 20 centimeters. It can be reared in an aquarium.