NUDIBRANCHS

No matter where you dive - how grey the habitat, high the sea or low the visibility - it always seems that if you look closely enough, you'll spot a small gaudy creature brightening up the vista. Nudibranchs are often referred to as 'butterflies of the sea' as their irridescent colours and bizarre patterns liven up almost any dive.

Part of the mollusc phylum, nudis are actually sea slugs and yes, pretty closely related to the nasty garden version. Their life cycles are short - just a month or two - despite all those bright colours and patterns indicating how poisonous they are to other species. All the same crabs, seastars and some fish will still nibble on them although mostly at the planktonic stage.

Some aren't quite so colourful but have adapted to mimic parts of the reef like soft corals and hydroids while others will disguise themslves by hosting smaller creatures like the solar powered nudi with his algae spotted body.

Although hermaphrodites, nudis still require a friend to reproduce. They extend a special tube from their side, exchange sperm sacs then crawl off to lay a lacy egg ring.

Spanish dancers and sea hares are closly related to the nudbranch group, as are flatworms. All have similar lifestyles, although flatworms and Spanish dancers both do that marvellous flamenco dance if you are lucky enough to spot them on the move at night.

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