crustaceans – a type of large arthropod, usually aquatic with a hard shell and typically ten legs

(Pronounced kruh-stay-shun)

Best examples of crustaceans include crabs and lobsters.

Note: As a rhyme hen rhymes with ten and the association is used to remember the number ten. 

To remember the meaning of crustaceans, associate it to a crab and use that mnemonic to remember that crustaceans are aquatic with a hard shell and typically ten legs. Use the following mnemonic:

The bread crusts were stale so I threw them in the ocean (crustacean); but the crabs loved them. The hen stood in envy.

Crustaceans are a major group within the arthropod phylum (see taxonomy) that are primarily aquatic animals, though some have adapted to terrestrial environments. They share the same arthropod features of a segmented body, jointed legs, and a hard exoskeleton, but are distinguished by having two pairs of antennae and specialised appendages for feeding. Most crustaceans breathe through gills and their exoskeleton is frequently reinforced with calcium carbonate, making it particularly hard and protective.

Crustaceans display remarkable diversity in size and form, ranging from microscopic water fleas to large lobsters, and they occupy various ecological roles as filter feeders, scavengers, predators and parasites. Common examples include crabs, lobsters, shrimp, barnacles and woodlice.