Starlet cushion star

Asterina gibbosa is a pentagonal starfish with short blunt arms and an inflated appearance. The aboral (upper) surface is clothed in groups of short, blunt spines. This starfish grows to a diameter of about 5 centimetres (2.0 in) and may be brown, green or orange. It is sometimes blotched with colour and individuals from deeper sea locations tend to be paler in colour. It can be distinguished from the closely related Asterina phylactica by the fact that it has two small spines on each of the plates surrounding its mouth, A. phylactica having no spines on these plates and having a plain olive-green aboral surface with a brown central star. A. gibbosa, at 5 centimetres (2.0 in) is considerably bigger than A. phylactica which seldom exceeds 15 mm (0.6 in). At one time the two were believed to be the same species but it was realised in 1979 that besides the differences in appearance, the two occupied different ecological niches and had different reproductive strategies.