The water vascular system of Knobbly Sea Star does more than just circulate nutrients—it also enables them to move. Thousands of tiny tube feet project from their underside. As water moves through their bodies, it creates shifts in pressure that may cause the tube feet to expand or contract. Sea stars can cling on to surfaces through vacuum and coordinate their feet to move slowly over substrates.

These sea stars feed on relatively large prey using a clever strategy called extra-oral feeding. With the help of their tube feet, they pry open shells and push their stomach out through their mouth to begin digestion. Once softened, the food is pulled back into their body, allowing the sea star to finish digestion and absorb nutrients.

Knobbly Sea Stars play a vital role in reef ecosystems and are an important bioindicator species for reef health. However, as their habitats are near the shore, they are vulnerable to degradation and human disturbance. This species is listed as Endangered in the Singapore Red Data Book.