A marine animal exhibits bilateral symmetry in its larval stage, but its adult form is radially symmetrical. Which of the following anatomical features is uniquely characteristic of the phylum to which this animal belongs?

Step-by-step solution

An animal that is bilaterally symmetrical in its larval stage but radially symmetrical as an adult belongs to the phylum Echinodermata. The most distinctive and unique feature of the phylum Echinodermata is the presence of a water vascular system, which helps in locomotion, capture and transport of food, and respiration. The water canal system is characteristic of Porifera (sponges). The presence of cnidoblasts is a unique feature of Coelenterata (Cnidaria), and jointed appendages are characteristic of Arthropoda.