Sea urchins are extremely sensitive to water conditions and are first to show signs of stress, seen when their spines are laid down or are shed. Sea urchins (echinoderms) are a group of marine invertebrates that can be found in almost every major marine habitat from the poles to the equator and from the inter-tidal zone to depths of more than 5,000 metres.
There are around 800 extant species and the group has a long and detailed fossil record stretching back many millions of years. All echinoderms have tube-feet and these play a very important role in feeding and respiration. Echinoids move by means of spines and climb and cling on to hard substrata by means of their tubefeet. The spines also offer the primary means of defence.
Sea urchins are herbivores and feed in a variety...Read More