The Two Oceans Aquarium has welcomed a new arrival – the shaggy sponge crab

The ocean can be treacherous for shaggy sponge crabs, and camouflage is key to staying safe from predators. Other ocean animals, like octopuses, are masters at blending in with their surroundings, but shaggy sponge crabs must accessorise to shield themselves. This is where a hat comes to the rescue!

The perfect form of camouflage

Shaggy sponge crabs create their own camouflage by carefully cutting and shaping sponge or seaweed to fit on their backs, almost like a hat! This natural armour disguises the crabs, providing them with protection from predators. However, donning or reattaching their "hats" when they fall off is no simple feat! A crab might need to grab the sponge with their claws, roll onto its back, flip itself over, and then right itself. Imagine doing that every day just to put on your shoes!

Are there other types of sponge crabs?

There are many species of sponge crabs within the Dromiidae family, famous for their chunky size and almost round bodies. The “sleepy sponge” is the heavyweight champion, growing up to about 20cm long, while the tiniest species can be less than a centimetre – talk about a size range!

What about the sponge?

You might worry about a sponge being chopped up to fit a crab’s back, but there’s no need to fret. Sponges are tough and resilient. They’ll continue to feed and thrive on the crab’s shell without any issues. In fact, this can develop into a symbiotic relationship in which both crab and sponge grow together, with the crab only trimming the sponge occasionally to maintain control.

One of the funniest things about sponge crabs is their occasional, unpredictable outbursts. Out of nowhere, they’ll go into full-throttle action mode, chasing after scuba divers and wildly swinging their claws as if they’re on an urgent mission. It’s like the ocean’s version of a crab having a meltdown during rush hour!

A sponge crab on the loose, chasing down a diver with determination!