Solar-powered Phyllodesmium

Image: Markus Fritze
Phyllodesmium longicirrum

Wow... can you believe there's a slug in there?

It's Phyllodesmium longicirrum, a nudibranch from Indo-Pacific waters.

Image: Steve Childs
There's his face

These slugs reach a length of more than 12 cm (5 in), which is already quite big for a nudibranch...

Image: Steve Childs

And it doesn't include the extraordinary collection of dreadlocks that cover their entire body.

These dreadlocks are known as "cerata". P. longicirrum is a kind of Aeolid nudibranch, and the thing about Aeolids is they lack gills.

Video: liquidguru

They take in oxygen directly through their skin, instead. Cerata increase an Aeolid's surface area and ensure they get all the oxygen they need.

But there's more to it than that. The cerata also contain parts of the slug's digestive gland. And with P. longicirrum's unusually thick and long cerata, that's a lot of digestive gland!

Video: Zane Kamat

So it's not all that surprising to learn that those cerata are packed full of algae, all supplying their slug landlord with lots of the food they manufacture via photosynthesis.

Image: prilfish
Chomping on some coral

P. longicirrum is not 100% solar-powered in this way, since they also feed on a soft coral called Sarcophyton. In fact, eating this coral is probably how they acquire all that algae in the first place!

It's nice to see a slug playing its role in saving the planet - and a nudibranch demonstrating that you don't need to be ridiculously colourful to be ridiculously extravagant!