Crustacean diversity refers to the wide variety of species within the class Malacostraca, which includes familiar animals like crabs, lobsters, and shrimp. These creatures are characterized by their hard exoskeletons, jointed limbs, and segmented bodies. Crustaceans inhabit various environments, from deep oceans to freshwater rivers and even terrestrial ecosystems. There are over 50,000 known species of crustaceans, showcasing a range of sizes and adaptations. Some, like the barnacle, are sessile, while others, like the krill, are vital to marine food webs. This diversity plays a crucial role in aquatic ecosystems and contributes to global biodiversity.