Tube foot

Tube foot is a structural component of the water vascular system of Echinoderms, a phylum of marine animals that includes starfish, sea urchins, sand dollars, and sea cucumbers.

Anatomy and Function

The tube foot consists of a hollow, elongated appendage that extends outward from the body of the echinoderm. Each tube foot is typically composed of an ampulla, a sac-like structure inside the body, and a podium, the external portion that interacts with the environment. The ampulla contracts to force water into the podium, causing it to extend. This hydraulic mechanism allows the echinoderm to move, adhere to surfaces, or manipulate objects.

Tube feet are often tipped with suckers which aid in locomotion and feeding. In some species, such as the crown-of-thorns starfish, the tube feet are adapted to deliver toxins to potential predators.

Distribution and Diversity

Tube feet are a characteristic feature of all echinoderms, but their number, arrangement, and specialization can vary widely among different species and classes. For example, starfish typically have rows of tube feet along the underside of each arm, while sea urchins have tube feet distributed across their entire body surface.

Ecological and Evolutionary Significance

The tube foot system is a key adaptation that has contributed to the success of echinoderms in a wide range of marine habitats, from tidal pools to the deep sea. It has evolved to perform a variety of functions, including locomotion, feeding, respiration, and sensory perception.

See Also

• Water vascular system
• Echinoderm
• Starfish
• Sea urchin
• Sea cucumber