Namibian Cushionstar

This type of sea star grows five arms and can reach up to 80.0 millimetres (3.15 in) in length, though most stay around 50 millimetres (2.0 in). The size is found to vary with depth, larger sea stars are found deeper while smaller ones are usually found in shallow waters. The can be found in a variety of colors, mainly white and brownish, but also can be an orange-red color.

All sea stars have tube feet that are controlled by hydraulic pressure. They can be found arranged in grooves along the arms. Tube feet are used to move around, they can attach to all different surfaces, feeding by passing food along the arms and to the mouth which is located at the center of the organism and for respiration. Sea stars do not have gills or lungs for respiration, they rely on their tube feet and papules, or skin gills, to take oxygen out of the surrounding water and move it into their bodies.

Asterina stellifera feeds on macroalgae, bryozoans, tunicates, polyps, and biofilm as well as different types of kelp.

Asterina stellifera is one of the few asteroid species found in the rocky coast of the South Atlantic Ocean. They stay in the coastal zones near rocky outcroppings and most can be found around 6–8 metres (20–26 ft) down.

Asterina stellifera has a defined annual and synchronous reproductive cycle. This cycle is affected by seawater temperature and day-length, they increase chances of fertilization by controlling gametogenesis (a process in which one cell splits to form four more cells). Reproduction is also regulated by planktonic food supply. A. stellifera can reproduce asexually by breaking apart into smaller parts and regrowing the missing limb. This explains why Asterina can be found living with less than five arms. Asterian sea stars also reproduce through dispersal of eggs. At the beginning of reproduction, many starfish belonging to the asteroid species form aggregations, nothing has been researched for A. stellifera but it can be assumed they would also mate like this. It is known that other Asterina species deposit up to 1000 eggs in a specific location in the process of reproduction.