tunicate science definition

Any of various primitive marine chordate animals of the subphylum Tunicata, having a rounded or cylindrical body that is enclosed in a tough outer covering. Tunicates start out life as free-swimming, tadpolelike animals with a notochord (a primitive backbone), but many, such as the sea squirts, lose the notochord and most of their nervous system as adults and become fixed to rocks or other objects. Tunicates often form colonies.