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The walls of the arches are covered with a spectacular diversity of plants and animals. Large red and orange sea fans emerge vertically from the rock and stinging hydroids form feather like colonies. Delicate sea-mosses and lace corals of a variety of shapes and colours cover many surfaces. These are actually colonies of minute zooids, most with feeding tentacles and a stomach, but others that specialise in reproduction, support or defence. Various sponges and gelatinous tunicates complete the scene.
Many of these creatures are brightly coloured, advertising their toxins to predatory animals that might be tempted to feast from this smorgasbord. However, many animals have evolved to deal with these toxins and consequently thrive in this environment. These include a variety of red, orange and purple seastars and a range of sculptured seasnails.
Fur seals can sometimes be seen enjoying this playground, torpedoing through the tunnels and in and out of the arches.
Stalked Hydroids (Ralpharia magnifica)
Resembling bunches of flowers, Stalked Hydroids are always found in groups of between two and 100 separate animals in the more sheltered sections of reefs. Adorned with pink tentacles, the large, cup-shaped feeding 'heads' grow on stalks up to 10 centimetres long. Their bases are tangled in the sponges and soft corals by a mass of filaments. By growing off the seafloor, Stalked Hydroids rise above their competitors and the stinging tentacles trap small floating animals before they reach creatures beneath.