noun, plural: arthropods
Arthropods are the invertebrates belonging to phylum Arthropoda. This phylum is regarded as the largest phylum of Kingdom Animalia. They include the insects, arachnids, myriapods, and crustaceans. They are generally characterized by the following features: (1) a hard chitinous exoskeleton, (2) segmentation, (3) multiple jointed (paired) appendages, and (4) open circulatory system. The arthropods have an exoskeleton, which is a hard outer casing used to protect their soft internal organs. The exoskeleton also serves as point of attachment for muscles, especially, those associated with moving the appendages. The exoskeleton of the arthropods is a cuticle made from layers of protein and chitin. Segmentation in arthropods enables specialization of organs and structures. The appendages or limbs of the arthropods arise from specific body segments. Their appendages are paired and jointed, and specialized for different functions, such as for walking, feeding, copulation, sensory reception, etc. Arthropods have an open circulatory system. The heart propels the hemolymph through the short arteries and then into the sinuses surrounding the heart and organs.
Arthropoda is comprised of the following major sub-phylum groups: Chelicerata (spiders, scorpions, etc.), Crustacea (shrimps, lobsters, crabs, etc.), Tracheata (includes insects and myriapods), and Trilobitomorpha (extinct trilobites).
Word origin: Latin arthropoda, from Ancient Greek árthron (“joint”) + poús (“foot”)
- Kingdom: Animalia
- Subkingdom: Eumetazoa