Nuts about Nudibranchs.

I was on Etsy recently and came across an artist who makes some incredible and unique marine themed jewellery.  Called indolentjellyfish, I guess the clue was in the name!  Using polymer clay to hand-make tiny, detailed pendants of marine invertebrates such as nautilus, cuttlefish, squid, octopus, nudibranchs and even mantis shrimp, I was blown away by the pieces.  I can definitely think of at least two friends who would covet one of the nudibranch necklaces!

It seems like the humble sea slug, or nudibranch as it is otherwise known, is the marmite of the sea.  Amongst divers there seems to be a distinct ‘love or hate’ attitude to these marine creatures.  You can easily tell by the underwater signal they use for them…if they deploy the ‘thumb squashing and grinding into their other palm’ signal then they are not in the nudibranch fan club!  But often if you like them, you really like them.  In a bizarre, ‘happily spend an hour face down in the muck scouring for them’ kind of way.  There are even people I’ve met who plan their entire holiday around which nudibranchs are next on their hotlist and where in the world they can go to have a chance of spotting them and getting photographs for their collection.  Divers who are not into them can’t understand how or why a slug could possibly elicit such devotion.


Kune’s Chromodoris nudibranch


Nudibranch egg rosette

I am in the ‘love’ camp.  Not enough to want to plan my holidays around them, but it does definitely make my dive if I manage to spot one that is new to me, unusual, or particularly beautiful.  It’s odd I guess, because slugs and snails on land do nothing for me, other than irritate me when they chew through all my plants.

But there is something special about nudibranchs.  And with more than 3,000 known species of nudibranch there are certainly plenty to choose from. With their pair of rhinophores on top of their head waving about in the current, and their frilly skirts, or mantle, rippling as they glide along, they seem to have an almost ethereal grace at times.  It might help that some of them are really very eye-catching.  They have also got some pretty interesting evolutionary quirks behind them to keep them safe and facilitate reproduction.  For example, they are actually simultaneous hermaphrodites, with both the male and female reproductive organs.  In the big wide spaces of our seas and oceans, this significantly increases their chances of successfully mating. After mating they will lay their eggs, either on or near the food source their food source of choice.  The coils of eggs can be thin white strands or beautiful colourful fat rosettes, depending on the species.


Hiding in plain sight

For the language geeks, the name nudibranch comes from the Latin for ‘naked’ nudus, and the Greek for ‘gills’, brankhia.  As they have no shells for protection from predators, they have had to evolve other defence mechanisms.  Some go for bold colours and are very easy to spot.  This is a classic warning in the natural world that a creature is toxic and best avoided.  Others go down the camouflage route, and can be very difficult to spot indeed, when blending into their chosen habitat.

There are also certain nudibranchs which feed on anemones and hydroids, consuming stinging cells, or nematocysts, in the process. Rather than just digesting and excreting them, the nudibranchs then achieve their own stinging super powers by storing these nematocysts to deploy when touched by a predator.

Nature really is quite incredible, I think, to have enabled something as tiny as a slug to develop such an amazing range of defence strategies and appearances.  Not so humble after all, if you ask me.


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