Question

How do sea star tube feet attach to substrates?

Short answer

In sea stars, the tube feet present at each arm regulates the organism’s adhesion to a substrate. The ampulla of tube feet directs water inside the podium, which causes it to expand. The expanded podium contacts the substrate, and the chemicals released by it attaches the sea star to the substrate.

Step-by-step solution

Echinodermata

The phylum Echinodermata is a part of the Deuterostomia clade (a lineage of bilateria). The organisms belonging to this phylum inhabit the marine ecosystem and exhibit the presence of true coelom along with radial symmetry.

The embryonic development is triploblastic, and the larva stage exhibits bilateral symmetry. These organisms have organ systems and have the potential to regenerate body segments.

Step 2:Characteristics of sea star

Sea stars are members of the phylum Echinodermata. These organisms have a star-like appearance due to the arms radiating outward the central body portion. Sea stars have a nervous system (only nerves and no brain), digestive system, and a water pumping system.

The absence of blood and heart is compensated by the water pumping system, as nutrients are absorbed from seawater that is pumped within the body. The presence of tube feet facilitates movement, substrate adhesion, and predation.

Role of tube feet in substrate adhesion

The tube feet are present in each arm of the sea star, and it has two structural parts; a podium and an ampulla. The function of the ampulla is to pull seawater towards the inside and fill it in the podium. The flow of water expands the podium structure and facilitates its contact with the substrate.

The actual adhesion occurs through the chemicals released by the podium. These chemical molecules enhance adhesive forces between the substrate and tube feet and thus, causes attachment of the sea star to the substrate.