The Green Sea Urchin (Psammechinus miliaris) is a marine (saltwater) echinoderm in the Parechinidae family. It is also known as the Shore Sea Urchin.
The Green Sea Urchin is spherical-shaped (ball-shaped). Its rounded “body” is called a test. The test is covered with short, thick spines of about the same length. It is purple-brown in shallow water and greenish in deeper water. The spines are a paler colour with purple tips. It has tubed feet in groups of five or six in a small arc shape. It has a small mouth. It does not have eyes. It is sensitive to touch, light, and chemicals due to the numerous sensitive cells in its spines, tube feet, and around its mouth.
It measures about 6 centimetres (2.5 inches) in diameter.
It is found in the Atlantic Ocean and the North Sea. It prefers shallow waters in tropical reefs and lagoons. It is benthic because it lives on the bottom of the ocean.
It can move, but very slowly. It crawls using its tube feet. It can survive many hours outside water.
The Green Sea Urchin is omnivorous, eating marine worms, crabs, snails, algae, and detritus (decaying matter).
The female Green Sea Urchin releases 80,000 to 2 million eggs into the water where the male fertilises them. The eggs hatch into echinopluteus larvae that settle on the sea floor. They undergo metamorphosis to become adult urchins.
Location of photographs: Parc Zoologique de Paris in Bois de Vincennes, France
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM