Brief SummaryRead full entry
BiologyThe common sea urchin browses on seaweeds and invertebrates (2), moving along the sea floor by means of 'tube feet', which project out from the spines (4). The mouth is located centrally on the underside of the test, and is furnished with a group of 5 specialised calcareous plates, known as an 'Aristotle's lantern' which acts as a jaw (4). The sexes are separate, breeding takes place in spring, and fertilisation is external (3). A microscopic four-armed larval stage forms; this 'echinopluteus' larva is free-swimming and makes up an important part of the plankton for around 8 weeks, before undergoing a complex metamorphosis into a small urchin (3). Maturity is reached at between 1 and 3 years of age, and estimates of maximum lifespan vary from 10 to 16 years of age (3).