Crustaceans have two pairs of antennae, three pairs of chewing appendages, and various numbers of walking legs. The legs are on the abdomen as well as the thorax. The labyrinth functions to regulate the osmotic condition of the body primarily, and secondarily to excrete salts, amino acids, and water. Millipedes and centipedes are both members of Uniramia, with bodies that consist of a head region followed by numerous segments with paired appendages. However, centipedes have one pair of legs per segment and are carnivores.
Most insects possess a tubular digestive tract that is somewhat coiled.
Insects that feed on juices low in protein have a greatly coiled tract to provide greater opportunity to absorb nutrients and to allow their digestive enzymes, which are weaker, more length over which to work. An instar in this context refers to stages between molts. The symmetry is radial and there is a five-part body plan in adult echinoderms. The skeleton is calcium-rich plates called ossicles that make up the internal skeleton covered by epidermis beset with numerous spines. Their nervous system is not centralized, with no head or brain, but rather the system is composed of central nerve rings that branch.