Sponge Crab and Decorator Crab

I was telling Pliny the Elder about my visit to the new Biodiversity Gallery in the SA Museum.

It was good, I said.

What did you learn? he asked.

That put me on the spot.

Umm, I learned ......

I tried to remember what I had learned. I had seen a great deal. A number of stuffed birds and snakes that I seemed to have seen before in earlier galleries. Drawers full of spiders and beetles and butterflies on pins. Numerous excited children and their parents. But what had I learned?

Suddenly I remembered the brightly coloured models of the Sponge Crab and the Decorator Crab.

There is a crab called the Sponge Crab, I said knowledgeably. It carries a sponge about on its back as a shelter. The sponge grows with the crab. If the sponge gets stolen, the crab will try very hard to get it back. If it can't, it will find itself another sponge.

Fascinating, said Pliny the Elder. What else?

There is another crab, called the Decorator Crab, that is equally strange, I told him. This crab uses snippers to snip off bits of seaweed that it finds, and sticks them to its back with glue that it secretes from a gland. It does this as a means of camouflage.

Snippers? said Pliny sharply. Where does it get the snippers?

Oops! I said. I can't remember that.