Many well-known animals belong to the group of invertebrates known as crustaceans Crabs lobsters shrimp and barnacles are among the most familiar crustaceans but the group also includes a large variety of other lesser known forms In fact there are some 45,000 species or kinds of crustaceans CROWDS OF CRUSTACEANS Crabs are some of the most familiar types of crustacean 4
The word crustacean comes from the Latin word crusta meaning shell All crustaceans have a hard but flexible exoskeleton or outer shell and two pairs of antennas or feelers Crustaceans are found mainly in water However a more specific definition of crustaceans is difficult This is because there are many differences in size features and habitats among crustaceans Shrimp have thin shells that they shed several times throughout their life Some animals other than crustaceans have shells too What are some similarities between a shrimp’s shell and a turtle’s shell What are some differences Compare and Contrast 5
CREATURES GREAT AND SMALL Crustaceans differ greatly in size The heaviest crustacean is the American lobster It can reach a weight of 44 pounds 20 kilograms The longest crustacean is the giant Japanese spider crab Its legs can stretch up to 12 feet 3 7 meters The Tasmanian giant crab can weigh as much as 31 pounds American lobsters like this one are found off the East Coast of North America 6
14 kilograms The average weight of the Alaskan king crab is 10 pounds 4 5 kilograms but it can grow to over 20 pounds 9 kilograms At the other end of the scale water fleas fairy shrimp and brine shrimp are some of the smallest crustaceans Most are shorter than 0 25 inch 6 millimeters Water fleas may only grow to be 0 009 inch 0 25 millimeter long Although water fleas are almost microscopic in size they are an important food source for many freshwater fishes Scientists are still discovering new species of crustaceans What is one reason that you think some species are hard to find Think About It This water flea is shown as about 15 times larger than its normal size 7
