No not THOSE kinds of crabs – THESE kinds of crabs!
Someone during OCEANDOTCOMM asked me what my favorite marine animal was, and I admit I felt a bit like a whale falling from the sky and couldn’t come up with words fast enough. After I regathered my brain I decided upon crabs. Crabs, especially deep-sea crabs, are completely unimpressed with humans, and have a sense of certainty about them that THEY are apex, despite what we humans might tell ourselves. Just ask this super gangster crab!
Crabs are a large group of loosely-related Crustaceans in the Decapoda order, which also includes shrimp, lobsters, crayfish, and prawns. These aquatic arthropods are mostly scavengers, filling an important role in healthy ecosystems
but some have been caught on camera trying to nab a fresher meal
Crabs are generally separated out into two groups – true crabs (Pleocymata) and…not true crabs (Anomura). (I don’t see them called “false” crabs anywhere so I guess they like to play in the gray space of taxonomy 😉)
“True crabs” is made up of nearly 7,000 species and includes some of the most important fisheries species in the U.S. – blue crabs, Dungeness crabs, and snow crabs
The…not true crabs have 472 species, which include king crabs (you know those giant legs you get at the buffet and joust with! …. oh no, just me?), squat lobsters, and everyone’s favorite middle school pet- hermit crabs!
While your first thought for hermit crabs might be the little guys in stinky terrariums, my favorite hermit crabs have got to the species from Parapaguridae. They have cnidarian symbionts (anemones and zoanthids) as their shell – no not ON their shell, AS their shell. I also think they’re adorable 💙
Another crab that deserves to be highlighted is the family Homolidae, also known as carrier crabs. These true crabs carry things in their back legs to act as decoys against predators. Those legs over time have changed in size to be smaller and have a little more bend in the “foot” which makes them very efficient in their carrying – and also makes the crab look like they’re wearing some A+ Derby hats! These hats can be made up of pieces of sponge, anemone or coral.
Crabs have hard exoskeletons made up of chitin, which is most similar to cellulose chemically, but I think of it as being similar to keratin in human nails. In order to grow larger, crabs have to periodically shed their exoskeleton, and during this time many species can also regrow missing claws or legs. How those pieces go missing….well…
This crab is probably trying to get a predator to leave it alone by leaving a tasty decoy, but crabs also seem to get themselves into trouble . Check out this overly curious buddy seen by ROV Hercules. And another crab that really wanted to get involved in some experiments!
How cool looking is that crab by the way?! I think it is genus Cyrtomaia, but I’m a coral biologist, so ¯\_(ツ)_/¯
I’ve personally had this Beuroisia sp. of crab try to fight the submarine I was in rather than just walk away. They’re just so pugilistic!
Crabs are most often solitary creatures but they have been seen aggregating quite a bit. The most famous is the Christmas Island red crab migration where they leave the forests to go spawn by the sea.
Or instead you may find an underwater crab army!
These spider crabs have gathered together for safety in numbers while they molt – this helps make it a little harder for them to get eaten – most of the time
Well – all this talk of crabs has made me hungry, so I think I’m off to red lobster!
What’s YOUR favorite crab?!?
a spoonful of ginger 
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