Invertebrate animals with an exoskeleton are called arthropods. The group includes around 25,000 species of crustaceans, such as crabs, lobsters, barnacles, and shrimps.
Crustacea are broadly free-living marine animals that vary in size from 0.1 mm to almost four (4) metres long.
Hard exoskeleton protects the crustaceans segmented body which is comprised of a head, a thorax and the abdomen.
The external skeleton does not grow but molts periodically and must be replaced by a new one.
Crustacean eyes are often extended on stalks and consist of multiple lenses (compound eyes).
Two pairs of extended antennae operate as feelers and sense organs.
Appendages on the abdomen, thorax and tail are used for walking, grabbing, and swimming in some species.
Saltwater crustaceans reproduce eggs which hatch into minute larvae that differ from the adult form.
Tasty seafood crustaceans such as lobsters, shrimps and crabs are farmed or caught for consumption. The edible scavengers are important as a human food source and a delicacy in some countries.
Fish and other marine animals eat small crustacea rich in nutrients known as copepods or krill. Copepods and other plankton are important tiny organisms or parasites that exist in the aquatic food chain.
There are more than seven thousand (7,000) different species of crabs, and most of them are members of a select group known as decapod crustaceans.
Even though humans eat a lot of seafood animals, including the blue crab, this section contains information about invertebrate crabs that scuba divers see living in the seas and oceans.
The marine species of shrimps have five (5) pairs of fragile legs known as 'swimmerets or pleopods' which it uses to swim and perch.
Crustacean Information |> Sea Shrimps |> Crabs |> Copepods |