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Which body features distinguish arthropods from other invertebrate animals?
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arthropod
Spiny lobster, or rock lobster (Palinurus elephas).
Arthropods are distinguished from other invertebrate animals primarily by their unique body plan and skeletal structure. The defining features of the phylum Arthropoda include:
- Jointed Exoskeleton: Arthropods possess a nonliving, organic exoskeleton composed of chitin bound to protein. This rigid covering provides support and protection but necessitates molting (ecdysis)āthe periodic shedding of the old skeletonāto allow the animal to grow.123
- Segmented Bodies and Jointed Appendages: The body is typically divided into distinct segments that bear paired, jointed appendages. The name "arthropod" literally means "jointed feet," reflecting these specialized limbs used for various functions, including locomotion and sensory perception.23
- Absence of Cilia: Unlike many other invertebrates, arthropods lack locomotory cilia, even during larval stages, a trait likely resulting from the presence of their exoskeleton.2
While arthropods share some characteristics with other invertebrates, such as the segmentation found in annelids, their reliance on a jointed, chitinous exoskeleton for support and movement sets them apart as a distinct and highly successful group within the animal kingdom.24