Question

How do tube feet help echinoderms move?

Answer 1

Hint: The marine invertebrate animals of the Phylum Echinodermata are called echinoderms. They are characterized by tube feet, a symmetrical body, and a calcite body covering.

Complete answer:
The Phylum Echinodermata involves animals that are exclusively marine, multicellular with specialized well-developed organs, and have the same characteristic features. Some of the characteristic features of these organisms are- triploblastic in nature, exclusively marine, organ level of organization, unsegmented body, calcium carbonate skeleton, open circulatory system, simple radial nervous system, excretory system absent, indirect development, power of regeneration in organisms, external fertilization, both sexual and asexual mode of reproduction. They are observed in different shapes- round, cylindrical, star-like with spines present. They are divided into five classes- Asteroidea, Ophiuroidea, Echinoidea, Crinoidea, and Holothuroidea. These organisms are found in sea depths and intertidal zones. The most common examples of echinoderms are- Sea Urchins, Sea stars, Sea cucumber, Brittle stars, Basket Stars, Sand dollars, etc.

Another characteristic feature of the echinoderms is the presence of a water vascular system. It serves the function of locomotion, respiration, absorption and transportation of nutrients and food, and elimination of waste particles. Tube feet are a special part of the water vascular system.

The small active tubular projections observed on the oral face of an echinoderm are called tube feet. Each foot of the tube feet has two major parts- ampulla and podium. The former has both- longitudinal and radial muscle, whereas the latter is the tube-like projection that contains longitudinal muscle only. These tube feet are also called podia, and they are filled with seawater. The main functions of the tube feet are- locomotion, respiration, and feeding and food transportation.

Tube feet assist in the locomotion of an organism by their extension. The hydraulic pressure helps in the extension and retraction of these sucker-like appendages. The alternative contraction of the muscles in tube feet results in the absorption of water through their surface, which leads to their extension. This extension helps them to get pushed against the ground and move forward. The relaxation of the muscles results in their retraction. The volume of water present in the tube feet decides their contraction and retraction. This constant extension and retraction of the tube feet provide movement to the echinoderms.

Note: The tube feet also helps in the attachment of the echinoderm to the surface. In some species, the tube feet are specialized to form respiratory tube feet that are thin-walled and are extremely flattened to provide a larger surface area for the absorption and exchange of gaseous substances. Some of the tube feet are specialized to capture prey.