How do crustaceans differ from insects, spiders, and centipedes?

Crustaceans are members of the subphylum Crustacea within the phylum Arthropoda. While they share the defining arthropod characteristics of a segmented body and a jointed exoskeleton made of chitin, they differ from insects, spiders, and centipedes in several key ways:

• Appendages: Crustaceans are distinguished by having two pairs of antennae (antennules and antennae) located in front of the mouth, as well as paired appendages near the mouth that function as jaws. In contrast, spiders lack antennae entirely, and insects and centipedes possess only one pair. Furthermore, crustacean appendages are primitively biramous (two-branched), whereas those of insects, spiders, and centipedes are typically uniramous (single-branched).12345
• Habitat: While insects, spiders, and centipedes are primarily terrestrial, crustaceans are predominantly aquatic, inhabiting marine and freshwater environments.536
• Body Structure: Unlike insects, which have a body divided into a head, thorax, and abdomen with six legs, or spiders, which have two body regions (cephalothorax and abdomen) and eight legs, crustaceans exhibit highly variable body plans often covered by a carapace. Centipedes are characterized by an elongate body with many segments, each bearing a single pair of legs.231