What are sea urchins?
Sea urchins belong to Phylum Echinodermata and Class Echinoidea which includes heart urchins and sand dollars. Features: Like other echinoderms, sea urchins are symmetrical along five axes, have tube feet and spines. And wow, do they have spines! Sea urchins are usually covered with lots of long, sharp spines that deter most predators. The spines also tend to break off inside their victim’s flesh. Some sea urchins have venomous spines that can inflict serious pain. Some sea urchins also have tiny jaw-like structures on stalks called pedicellariae. The main function of these is to keep the body of the sea urchin free of debris and parasites. They may also be used to collect food. Some sea urchins have larger venomous pedicellariae which painfully sting large creatures and can paralyse smaller ones. Test of Strength: Sea urchins have an internal skeleton (called the test) formed out of large ossicles fused together in plates. These form a pattern that resembles a sliced orange, in multip
