Butterflies of the Ocean

Glossodoris atromarginata, Nudibranch, Bare Island, Sydney, Australia

 If you’ve ended up here because of the word “Nudi” you’re sort of in luck. Nudibranch does come from the word “nudus”, latin for naked. So well done so far. Unfortunately “brankhia” is greek for gills, so “nude gills”. If you’re looking for any other form of nude best to head back to Google.

 
If you’re still reading this, nude gills probably doesn’t sound too exciting. Well, it gets worse. These are slugs, soft bodied animals crawling around underwater much like the slugs in your garden. What’s different about these slugs is that they come in amazing colours, shapes and sizes. Beautiful colourings, like a circus clown that’s in going out clothes that they never take off, not even for bed time. And there seems to be no limit to the colours. Deep red, bright blue, pure whites, blacks, green, yellows and everything in between. These slugs are so popular that they even have their own toy lines just like Paris Hilton.
 

And just like Paris Hilton they are a bit unusual in what they like in a mate. Nudibranch’s are simultaneous hermaphrodites, meaning they have both male and female sexual organs. However nudibranch’s can’t self-fertilise. They need another nudibranch to fertilise their eggs. Before you read on, important to know that the next few paragraphs will delve into the sex lives of nudibranchs. Please note – Nudibranchs wield their sexual organs much like a medieval warrior charging into the enemy swinging an axe. You have been warned….

The mating act itself, as the penis is shaped like a syringe, involves the penis being stabbed into the female genitalia. Then to keep it in place the penis has hooks and spines. (Cue the Marvin Gaye music ).
 
There is only one word in the english language that sums up this mating process – and that word is ouch.
 
One type of nudibranch, “Chromodoris reticulate”, would be a proud member of our consumer society. It has developed a disposable penis, which after mating it detaches and starts growing another, ready for the next encounter. Should this be considered littering? 
 
But life for the nudibranch is not all sex (although a fair bit of it is as they mate up to three times a day). They also have to eat. And eat they do but strictly no vegetables as any proud parent introducing broccoli to their child can appreciate. All nudibranchs are carnivores, eating other animals such as sponges, blue bottles and also their own kind. Food sources that contain poisonous capsules, such as nematocysts, are used to enhance the nudibranch’s defences. The capsules pass through the gut intact and are pushed out to the skin, ready to fire a poisonous barbed thread into any would-be attacker. Another example is a recent study from Queensland which showed that nudibranch’s digest toxins from the sponges they eat that pass harmlessly through their digestive system and are pushed to the slugs extremities, ready to deter any would be predators.
 
So what is it with all the colors? For reference, let’s have a look at how Bart Simpson deals with a brightly colored clown. That’s right – not well. Nudibranch’s have a similiar approach. Their colorful wardrobe serves as a warning to predators that they are poisonous and/or not that tasty.
Many  nudibranchs take on the colour comes from their food sources. This means they inherit the warnings that the color represents in what they have eaten.
So what about Botany Bay in Sydney Australia? Well, its full of Nudibranch’s and some of those are below. The colors are simply amazing.

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