Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. Most are small greyish or whitish animals with rigid, segmented exoskeletons. They have two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax. Isopods have various feeding methods: some eat dead or decaying plant and animal matter, others are grazers, or filter feeders, a few are predators, and some are internal or external parasites, mostly of fishes. Aquatic species mostly live on the seabed or bottom of freshwater bodies of water, but some more derived taxa can swim for a short distance. Terrestrial forms m