Environment Park Subotopic Layout
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The top of the reef is covered with a network of small boulders, seaweed beds, crevices and pools. In many places the small brown algae Neptunes Necklace (Hormosira banksii) covers the reef and provides protection for underlying invertebrates. The wide variety of spaces within the reef gives rise to a great diversity of animals under the rocks, attached to the sides, in pools, or hidden in cracks.
Keyhole limpets, crabs and mussels are abundant. Banded Brittle stars and carnivorous worms emerge from under rocks to feed nightly at high tide. The site is also known for its diversity of sea slugs known as opisthobranchs, which unlike the garden slug, appears here in a range of exquisite shapes, colours and sizes.
On the sides of the reef, brown seaweeds with zigzag stems grow profusely on the rocks, giving way to bright green Sea Nymph seagrass beds covering the sand. Eagle Rays patrol the outer reef edge.
Short-tailed Sea-Slug or Nudibranch (Ceratosoma brevicaudatum)
Delicate, beautiful and brilliantly coloured, the sea-slug is one of the larger, more vivid species of nudibranchs to be found at Point Danger. Growing to 15 centimetres in length, they have two tentacles at the front of the head which are chemical sensory organs important in finding food and a mate. The short-tailed sea slug is one of the most conspicuous of all seaslugs because of its large size and bright colours. Its pattern varies but generally has a pink/orange background covered in red, white edged spots.
The term 'Nudibranch' (pronounced noo - dee - brank) is often used to describe the group of marine molluscs that the short tailed sea slug belongs to. These animals have an external pair of feathery gills that are used by the animals to obtain oxygen from the water. In most marine molluscs the gills are hidden inside the body or beneath the shell. Nudibranchs have naked gills hence their name.
Nudibranchs are one of the few creatures that can actually eat sponges - usually avoided as a prey because of the toxic chemicals they contain. Some species of sponges also contain glass like needles. Nudibranchs are capable of not only extracting the toxic chemicals contained in the sponge's 'body' but also turning it to use in its own defence. They are unpalatable, even poisonous, to fish and their conspicuous, brightly coloured dots advertise this to would-be predators.
Ceratosoma are hermaphrodites and two animals mating play both male and female roles. The eggs are generally orange in colour and are layed in a circular belt of jelly.