question_answer 42)

  The locomotory organs of Echinodermata are (a) tube feet                      (b) muscular feet             (c) jointed legs                  (d) parapodia

Answer:

  (a) Tube feets are locomotary organs of echinoderms they are spiny-skinned marine animals. They have an exoskeleton of calcareous plates from which the spines arise. The adults are radially symmetrical, while the larvae are bilaterally symmetrical. Most echinoderms are sessile as they live in groups, while others are solitary. A unique feature of echinoderms is the water vascular system. It is a complex system of water-containing tubes and bladders which pass through pores in the skeleton. On the outside, these tubes look like feet. These tube feet are used for locomotion, exchange of gases and feeding. In most echinoderms the mouth is on the lower surface and the anus is on the upper surface. Echinoderms reproduce sexually and the sexes are separate. Some echinoderms like starfish (Asterias) and brittle stars (e.g., Ophiura) have arms arising from a central disc. While other sea urchins (Echinus), heart urchins (Echinocardium) and sea cucumbers (Holothuria) do not have arms. Sea cucumbers have tentacles near the mouth.