Are Hermit Crabs Actually Crabs? (The Surprising Answer)
No, hermit crabs are not true crabs – despite the name. They are close cousins of crabs, but scientists put them in a separate group nicknamed the “false crabs”. In fact, hermit crabs are just as closely related to squat lobsters as they are to the crabs at the seafood counter. So why do they look so crabby, and how can you tell them apart? Here is the full story, explained simply.
So What Are Hermit Crabs, Really?
Hermit crabs are crustaceans – the same broad family as crabs, lobsters, shrimp, and crayfish. So that part of the name actually fits just fine.
But within that family, real crabs and hermit crabs sit on two different branches. Scientists call the true crab branch Brachyura, and the hermit crab branch Anomura – the “false crabs.”
The two branches are close cousins, but they are not the same animal. On the hermit crab branch, you will also find squat lobsters, porcelain crabs, king crabs, and mole crabs.
Bonus: Do Hermit Crabs Have Brains?Â
True Crabs vs Hermit Crabs: The Key Differences
Here is how a real crab and a hermit crab differ at a glance:
| Feature | True Crab | Hermit Crab |
| Group | Brachyura | Anomura |
| Abdomen | Hard, tucked under | Soft, curled, exposed |
| Shell | Own hard shell | Borrowed snail shell |
| Visible legs | 10 (5 pairs) | Usually 8 visible |
| Body | Wide, flat | Long, lobster-like |
Why Hermit Crabs Are Not True Crabs
A few key differences set them apart from real crabs:
- Soft, curled abdomen. True crabs have a hard abdomen tucked flat under their body. Hermit crabs have a soft, spiral abdomen that needs a borrowed shell for protection. This is the single biggest difference.
- They borrow their shells. Real crabs grow their own hard shell. Hermit crabs cannot, so they move into empty snail shells and upgrade to bigger ones as they grow.
- Different leg count on show. True crabs show all 10 legs. Hermit crabs keep their last pair tiny and hidden inside the shell to clean their gills, so usually only 8 legs are visible.
- A lobster-like body. Under the shell, a hermit crab’s long, curved body looks more like a lobster than a flat, round crab.
Bonus: Types of Hermit Crabs
Why Do They Look So Crab-Like Then?
This is the fascinating part. Hermit crabs look crabby because of a process scientists call carcinization – a fancy word for a simple idea.
Completely unrelated animals can slowly evolve a crab-like shape on their own, just because that shape works so well. A crab body sits low and moves sideways easily, which helps it dodge predators.
It has happened so often in nature that scientists joke evolution “keeps inventing crabs.” King crabs, porcelain crabs, and the hairy stone crab each became crab-shaped on their own – and hermit crabs picked up some crabby looks too, without ever becoming true crabs.
What Are Hermit Crabs Most Related To?
Their closest relatives are the other “false crabs”: squat lobsters, porcelain crabs, king crabs, and mole crabs.
Here is a fun surprise – the giant coconut crab is actually a type of land hermit crab that grew so big it no longer needs a shell.
Hermit crabs and true crabs did share an ancestor long ago, but they split apart over 200 million years ago, back in the age of the early dinosaurs. That makes them distant cousins, not the same animal.
The Easy Way to Spot a False Crab
Want a quick trick? Count the visible legs. A true crab shows 10 legs (including the claws).
A “false crab” like a hermit crab usually shows only 8, because the last pair is shrunken and hidden away for gill cleaning. So if you spot a “crab” with just 8 visible legs, you are almost certainly looking at a false crab.
Conclusion
So, are hermit crabs actually crabs? Not true crabs, no. They are crab cousins, but they belong to the “false crab” group, while real crabs are “true crabs.”
Hermit crabs actually sit on the same branch as squat lobsters, and they only look crabby because that shape works well in nature. Their soft body and borrowed-shell lifestyle make them one of the most unique – and most interesting – animals on the beach.
(FAQs):
A: Yes. Hermit crabs are crustaceans, the same broad group as crabs, lobsters, and shrimp. They are just not true crabs – they sit on a separate branch of the family tree.
A: Their closest relatives are squat lobsters, porcelain crabs, king crabs, and mole crabs – the other “false crabs.” The giant coconut crab is a close relative too, and it is actually a land hermit crab.
A: It comes down to looks. Over millions of years they slowly evolved a crab-like shape, so people naturally called them crabs. The name stuck long before science sorted out the family tree.
