Blue Sea Slug

Image via Wikipedia

The Blue Sea Slug, also known as the Blue Ocean Slug, Blue Glaucus, Sea Swallow, Sea Lizard and Sea Dragon, not to mention Glaucus atlanticus. Wow! That's quite a collection! It only takes a quick look to understand why such a creature would amass so many names: it's absolutely gorgeous! Careful though, because this beauty has a sting in its... fingers?

First, we should note that this really is a slug. A dramatically beautiful, blue, nudibranch sea slug that can be found floating along in the world's oceans. They are actually upside down, the blue foot facing up and the silvery back facing down. This colouring helps with camouflage from above and below. They are only a few centimetres long and float using surface tension and a sac of gas in its stomach. It's really heartening to see stomach gas put to such good use! I can't help but feel I've been missing a trick...

Image by tarotastic via Flickr

From the body extend all those lovely sticky-out bits and what can only be called a long tail. Most slugs just have a nasty end that doesn't have the eyes on it, but the Blue Sea Slug looks like it has a real tail. But watch out! The tips of these tendrils are armed with nematocysts, the specialised stinging cells that can only be found on cnidarians. But the Blue Sea Slug isn't a cnidarian, so how does it get its weird hand type things on them?

To answer this question you have to realise that this gastropod is a top predator in its particular arena. They eat all sorts of other floating oddities such as the Violet Sea Snail, the Blue Button and the By-the-wind Sailor. Special attention, however, is given to the mighty Portuguese Man o' War.

paulhypnos
Video also includes the Blue Button

Once detected, the Blue Sea Slug will slowly make its way to prey using its big wing, jazz hand things, which are also called palps or cerata. I prefer jazz hands, though. Small prey can be eaten whole, large prey can be cut apart with the radula - the tough, toothy, tongue that molluscs have.

Image by lostandcold via Flickr

It can do this even with cnidarians, because this slug is completely immune to their stings. In fact, Portuguese Man o' Wars are their favourite food! Not only can they munch into those tentacles, they even pick out the most powerful stinging cells they can find. Once eaten, the stomach somehow knows not to digest the nematocysts. They are instead moved into the jazz hands/cerata and make their way to the fingertips. Here, the stings are stored for use against predators. They are even more effective (painful) than they were on the Portuguese Man o' War, since the Blue Sea Slug can select the very best ones and leave the less developed ones alone.

Kinda sounds like 'Sea Swallow' is missing something out that 'Sea Dragon' better encapsulates.

Are dragons hermaphrodite? Blue Sea Slugs are. They are also very well endowed since they can't actually stop doing the jazz hands manoeuvre, there's quite a big gap to bridge. Once they've done that they will both be ready to lay a long chain of floating eggs, from which the larvae will hatch.

The larvae actually have shells, like snails! But soon they grow out of their security blankets, get their dance moves on, stretch out those extraordinary limbs of theirs and go about the very important task of packing them full of poison.

It's dapper, it's surrounded in flowing tendrils and it emits pain and poison from it's finger tips. Surely we can add Sea Wizard and Sea Sorcerer to its list of names?