Purple sea urchin

Biology

When it is young, the purple sea urchin has green spines. Only in adulthood do they acquire the colour that names this species. It grows up to 50 millimetres in diametre and reaches sexual maturity by the age of two years. This sea urchin is found in large groups near kelp forests where the food source is abundant, or alone in the low tide area.

Conservation

Like the red sea urchin, this species also feeds on the brown algae which form the kelp forests it lives in. When its number significantly increases, this can lead to the destruction of that habitat. They are highly valued in the sushi industry, especially in Japan.

Curiosities

This species has a particular behaviour. It uses its five teeth in concert with its spines to gauge and scrape away the substrate. The result of this is a depression in the rocks into which the shell of the urchin can firmly settle. This behaviour allows the purple sea urchin to hold firmly to the substrate, even when the sea is very rough.