Nudibranch - naked and nasty!

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Today I touched the buffalobster
and the goldfishark,
the eagleopard, ocelotter,
and the weaselark.
Ken Nesbitt

The underwater circus theme is continuing in this blog entry; last week I talked about acrobatic manta rays, this time I am looking at the tiny clowns of the sea; the spectacular nudibranchs!

‘Nudibranch’…the word sounds exotic and strange, but if you translate it into English, it actually means ‘naked gill’. This creature possesses thin tufts that stick up from its back. These tufts act as gills, free to waft around unprotected in the currents, allowing oxygen to be collected from the surrounding water so it can breathe.

A nudibranch looks like a worm done up in brightly coloured clothing, covered in stripes and swirls of red, blue, yellow and green. But appearances can be deceptive; these creatures aren’t worms at all, they are actually related to the rather unexciting brown snails you find in your back garden. The main difference is, they lack an external shell to protect them from passing hungry mouths.

But don’t be misled; these tiny creatures are far from defenceless. They possess a dazzling array of tools to fight off potential predators. First, there is the use of colour - bright poster colours, like those you seen on a clown costume, warn all passers-by that the nudibranch is not a tasty meal but a mass of poisons. Now picture this: you find a bumble bee, steal and swallow its poisonous barb and in no time at all the barb appears from you finger tip so you can sting anyone that annoys you. Impossible? Well this is exactly what some species of nudibranch do; they take the stings of creatures they eat, and incorporate them into their own body to defend themselves at a later date. And if that seems bizarre, what about the individuals that will shed a part of their body when they are under attack, to confuse the predator - it would be like you dropping an arm to distract a marauding tiger!

Nudibranchs are found from the reef to the open sea and not all advertise their presence with brilliant splashes of colour. A species found floating in the surface waters of the ocean exhibit countershading similar to that found in the flying fish we discussed a few months ago: dark on the top side to blend with the ocean, light on the underside to blend with the sky. Other groups are able to change their colour like a chameleon to blend in with their surroundings.

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