Moon-headed Sidegill Slug

Image: berniedup
Euselenops luniceps

It's a chocolate chip pancake with rolled, chocolate wafers in! Delicious! But what is it doing on the sea floor when I have a perfectly good plate right here?

If you go to warm, sandy, Indo-Pacific waters at night you'll have a chance of seeing this delicious-looking slug wandering around on the seabed. They reach about 3 to 7 cm (1 to 3 in) long, so it'll make for the perfect midnight snack if you happen to suffer from the same kind of bad habits I do.

Image: Nick Hobgood

It looks like they have a pair of chocolatey eyes on one end and a chocolatey tail on the other. In fact, the "eyes" are actually rhinophores, which smell and taste the water around them. The tail is really a siphon, which takes in oxygen-rich water and passes it over to the gills.

Image: wildsingapore
Fluffy, yellow gills

You can see the gills in between the large foot and the smaller mantle which sits on top. The Moon-headed Sidegill Slug is a member of the Pleurobranchidae family, which are known as Sidegill Slugs because they all have their gills on just the right hand side of their body.

Image: berniedup

This particular Sidegill Slug has a great, big crescent moon for a face. This huge flap of skin completely covers the mouth and is known as the veil. You might notice that it looks a little frayed at the edges; these are called papillae, little sticky-out bits which can taste the floor as they glide across it. It means the slug can taste things before deciding whether or not to put it in their mouth.

Sounds like a good idea to me. I wouldn't want to do something silly like bite into a slug because I thought it looked like a pancake. No, sirree...

Video: ScubaMauiDreams

Now the Moon-headed Sidegill Slug can roam around and munch on any little creatures unfortunate enough to find themselves on the wrong side of the veil.

But it isn't easy when you look as tasty and chocolatey as the Moon-headed Sidegill Slug. So they need a few tricks of their own.

One thing they can do is swim away. The foot is so big and so thin that a bit of flapping launches them up and away.

Image: PacificKlaus
Going down

But what they really like is to burrow into the fine sand beneath their foot. They can cover their entire body, leaving nothing but the rhinophores and the siphon poking out. The rhinophores act as a kind of smell-o-vision periscope, while the siphon is like a snorkel. The Moon-headed Sidegill Slug can stay there pretty well as long as it likes and still have an idea of what's going on around it!

Over, under, around... this pancake has options!