Think you know everything about this common crustacean? Think again.

Here are 10 quick facts about the crab:
1. Porcelain crab filter-feed by using long feathery appendages to comb the water for plankton.
2. Crabs don’t have teeth, but instead grind their food in a stomach chamber called a gastric mill.
3. A crab’s outer shell, or exoskeleton, does not grow, so the crab grows by shedding its old shell in a process called moulting.
4. Divers occasionally may come across the discarded shell, which looks like a dead crab.
5. The Japanese spider crab, known to achieve a leg span of almost 13 feet, is the largest known arthropod in the world.
6. Guard crabs live symbiotically with hard corals and will defend the coral against predators such as the crown-of-thorns starfish.
7. Crabs walk sideways because that’s the only way they can — their leg joints are hinged in such a way that only sideways movement is possible.
8. Blue, King, Dungeness — all of those crabs we love to eat are in phylum Arthropoda … along with the cockroach, housefly and spider.
9. Some crabs in the Majidae family are called decorator crabs because they camouflage themselves by attaching small sponges, anemones, hydroids and other animals to their carpaces and legs.
10. Not all hermit crabs live in shells. The coral hermit lives in abandoned worm tubes or self-created holes in living coral.

For more info and facts on marine life follow the undersea adventures of Ned and Anna DeLoach at marinelifeblog.com.