What Is This?

This bright, bobbly surface looks like something from another planet—but it's actually a photograph of something that's quite common on Earth. Can you work out what it is?

Sadly for you, we're going to let you puzzle over the answer for a little while. To give you a helping hand, the images were captured by a zoologist and... actually, that's a big enough clue.

We'll post the solution here in a couple of hours or so. Until then, try and work out exactly what it is amongst yourselves in the comments-without cheating and resorting to Google Images.

Update: Here's the answer.