Rough mushroom coral

The rough mushroom coral (Ctenactis echinata) is an elongated, 15–30 cm, shoe-sole-shaped coral which, unlike the tongue mushroom coral, has a single long mouth slit running down its centre. It earned the name "rough" from its coarse ribs covered in sawtooth-like spines – in low light it looks like a spiky comb laid on the sand. Its colour is usually brownish or tan, often paler around the mouth slit.

This species is free-living too: the juvenile sits on a stalk on the rock, then breaks off and spends the rest of its life lying on the rubble. Its biological sensation lies elsewhere, though: the rough mushroom coral is one of the best-documented sex-changing corals. Smaller individuals are mostly male and may turn female as they grow – and after stress or injury they can even switch back. In the coral world this is exceptional flexibility, described in detail by researchers on precisely this species.

Around Hurghada you will find it on the sand and rubble patches of the more sheltered reefs at 3–20 metres – it can drift into view even while snorkeling on the plateaus between the towers of El Aruk or in the "aquarium" of Gota Abu Ramada. As a free-living coral it is protected by the same rule as its relatives: it is happiest without fin kicks, stirred-up sand and curious hands.