Platygyra daedalea usually forms massive dome or boulder-shaped colonies which may be a metre (yard) or more in diameter however, sometimes it forms flattened plates or it may be encrusting. The polyps are situated in meandering valleys with low walls between them which are often perforated. The septa are toothed and protuberant, usually with uneven or pointed tips. There is an obvious ridge, the columella, in the centre of the valley. The colour varies and there may be contrasting valleys and ridges. This coral can be distinguished from the similar but less common Platygyra lamellina by the fact that the valleys are wider and the walls between them have more vertical sides and have flatter tops. P. daedalea is an aggressive coral and seeks to prevent competitors from overshadowing it. Researchers placed small colonies of this species alongside similar-sized colonies of the less-aggressive Favites complanata. Some of the tentacles of P. daedalea developed into sweeper tentacles which then inflicted damage on the soft tissues of the adjoining F. complanata. These sweeper tentacles were up to 90 millimetres (3.5 in) in length, about fifteen times as long as a normal tentacle, and well armed with cnidocytes. The soft tissue damage was extensive, the skeleton was laid bare in places and sponges, algae and other fouling organisms grew on it. Three of the ten corals that were attacked eventually died. Learn more about Brain Coral