What are features of arthropoda?

Arthropods are characterized by segmented bodies, an exoskeleton made from chitin, and joint appendages. They have an internal body cavity (hemocoel) and an open circulatory system which employs hemolymph, a fluid that does not distinguish between interstitial fluid like lymph and oxygen carrying fluid like blood as in most vertebrates. They use a copper-based oxygen carrier molecule instead of the iron-based hemoglobin, which floats freely around in the hemolymph and is not bound to blood cell proteins. They do not have a dedicated and separate branch of their circulatory system just to oxygenate; internal organs (and cells) are simply bathed in this fluid; many arthropods (e.g., insects) oxygenate directly from the air through tubules connected to holes (spiracles) in their body segments. Their nervous system is 'ladder-like' on their ventral surface, and their brains formed around the esophagus from fused segment nerve ganglia.