A Creative Crustacean
Most sea creatures prefer to stay free of debris, but the masking crab, also called the moss crab, takes the opposite approach. Rather than removing organisms from their shells, moss crabs attach items and living organisms to themselves. This behavior acts as camouflage, helping the slow-moving crab blend into its surroundings and avoid predators.
“Moss crabs are known for decorating their shells by attaching other organisms such as algae, sponges and bryozoans to their shells, helping them to blend in with their environments,” explains the University of Michigan’s Animal Diversity Web.
A Chef’s Hat Under the Sea
Last month, scuba diver Cassie Brown encountered a particularly amusing example. While exploring underwater, she came across a moss crab sporting a giant white anemone on its head, resembling a chef’s hat.
“Among the more anomalous and HILARIOUS things I’ve seen underwater: a giant masking crab wearing a metridium like a chef’s hat!” Brown wrote on Instagram.
Brown observed from a distance as the crab crawled along, proudly displaying its unusual headpiece.
How the Crab Keeps Its Decor in Place
Despite the smooth, slippery surface of its shell, the crab’s adornments don’t slip off thanks to hooked setae, tiny hair-like structures that secure the decorations in place.
“They do not use an adhesive material to attach decorations, instead using their hooked setae to secure materials and other organisms,” Animal Diversity Web explains.
A Symbiotic Relationship
The crab benefits from its decorated shell, distracting predators and prey alike. Meanwhile, the anemone thrives, gaining access to water currents and leftover food from the crab’s meals. This is an example of a mutually beneficial relationship, or symbiosis.
“Many of these interactions are symbiotic, in which anemones and sponges benefit from constant water currents via the crab’s walking motion and are able to take advantage of leftovers of the crab’s meal,” notes Sanctuary Simon.
A Delight for Observers
For divers like Brown, seeing the moss crab’s creativity was a highlight of the dive.
“What a weird and welcome reminder that the ocean owes me nothing but gives me everything,” she wrote.
This tiny underwater “chef” reminds us that the ocean is full of surprises — some practical, some whimsical, and all fascinating.
