The cushion star (Asterina gibbosa) is a small starfish, or echinoderm, that is commonly found in rockpools on all western and southern UK coasts and are the only true starfish found in the intertidal zone. They can grow to around 5cm (or 2 inches) with 5 arms that are covered in short spines and can be a range of colours; orange, brown, green or cream so are very good at camouflaging into their surroundings! The cushion star can be commonly mistaken for Asterina phylactica but you can distinguish them by turning the starfish upside down to see its mouth in the center. Each mouth plate should have two spines, whereas Asterina phylactica has no spines! You can also see lots of little tube feet which help them move around.
Kingdom: Animalia (Animals)
Phylum: Echinodermata (Echinoderm)
Subphylum: Eleutherozoa (Mobile animals with a mouth pointing towards substrate)
Class: Asteroidea (Starfish)
Order: Valvatida (Starfish with visible ossicles)
Family: Asterinidae (flattened starfish)
Species: Asterina gibbosa
You can normally find cushion stars underneath big rocks, in tiny spaces or on overhangs in a rockpool. They are very good at hiding and can sometimes be underneath algae or seaweed. Because they are nocturnal, you may have more luck finding them at night or dusk.
Cushion stars are opportunistic feeders, meaning they eat just about anything they can get that isn’t already alive. This can range from dead crabs to seaweed to bacteria. Their favourite food are diatoms and they feed by turning its stomach inside out and secreting digestive enzymes.