What do sea urchins look like

Most remarkably, these spines are each attached to the urchin by a ball joint, allowing them to be pointed in any direction. If an urchin is touched unexpectedly, all spines will reorient themselves to point towards the source of touch. The resilience of sea urchins makes them well suited to South Africa's diverse ocean habitats, like our unique kelp forests.

But these spines are not only for protection, they are also for navigation. Sea urchins do not have eyes - in fact, they rely almost completely on the fact that the skin on their five armoured plates is light-sensitive enough to allow some vague navigation, like "seeing" a dark patch that could indicate a piece of seaweed or a sheltered cave to hide in.

This low-resolution vision makes navigation very difficult for sea urchins, especially when there isn't much lighting contrast in their environment. By "pointing" their spines in one direction and slowly moving them, the urchin can become much more sensitive to the direction light is coming from - and this makes navigation easier for urchins that have longer spines. If you're searching for urchins, be sure to pay ours a visit! Plan Your Trip. Special Offers. Online Resources.

Things To Do. School Lessons and Outreach. Tourism Professionals. Feeding Times. Conservation Work. Web design and content by Flow Communications. Search Two Oceans Aquarium Toggle navigation. Home Blog Microscopic marvel: A very close look at sea urchins. Tiny feet Sea urchins' bodies are covered in tube feet, small tentacles with a suction cup-like end that they can extend beyond their spines to move themselves along the sea floor, climb obstacles and even roll themselves over with if they are flipped.

The porous madreporite of a sea urchin seen under the microscope in our Skretting Diversity Gallery. View all species. Buy official tickets online. Sign up for our newsletter: Subscribe.

This site uses cookies to enhance your experience and to personalize content and ads so that our partners can provide you with the very best opportunities and services you may otherwise be unaware of. OK Learn more No Thanks. Sea urchins also commonly lodge themselves half way into the surface of sand, mud or holes. This way they can be protected from large waves or currents. Sea urchins also live in areas where they can find sources of algae, sea grass, seaweed and other foods they can consume.

One other very important characteristic of the sea urchin is that it is nocturnal. Sea urchins will usually hide in holes or crevasses during the day and only feed at night. A common place to find a sea urchin as well is in coral reefs. Examples of where sea urchins are very commonly found are on the reefs of Hawaii, of the Caribbean and of Australia. Sea urchins have several adaptations to help them survive. To protect themselves from predators, sea urchins will react immediately if something sharp touches their shell and they will point all of their spines towards the area being poked.

They are also light-sensitive. This is why they are nocturnal. This light sensitivity also allows sea urchins to move their spines in reaction to shadows. In order to protect themselves from being swept away from the powerful ocean currents and waves, sea urchins lodge themselves into holes or crevasses. Finally sea urchins, somewhat like starfish, have a certain regenerative ability. If a spine is damaged or lost, a sea urchin can re-build it.

Like most creatures, sea urchins are vital for the survival of other living creatures surrounding them. They have many predators and due to this, if the sea urchin population decreased, the sea creatures that feed on them might begin to die out as well.

A few predators that feed on sea urchins are sea otters, star fish and humans. At one point there was almost a density of eighty sea urchins per square meter. This immense number of sea urchins began to eliminate the sea weed which lived in the same area. They were also eroding the coral reef. Luckily before any huge damage had occurred, there was a mass die-off of sea urchins in the area believed to be caused by a water-carried disease.

Sea urchins have also been reported to cause erosion of reefs in places such as the eastern Pacific, Kenya and the Red sea. So although sea urchins are important to the survival of an ecosystem, they can also become dangerous in great numbers.

At the moment sea urchins are very populous and located all over the world in many different oceans. Therefore they seem to be in no immediate danger of disappearing or becoming endangered in general. However in the past sea urchins have shown mass mortality due to an increased amount of pollution in the oceans and also due to an increased amount of fishing by humans.

Hurricanes and a rise in the temperature of water have also wiped out a great amount of sea urchins. Evidently sea urchins are very susceptible to change, and with global warming, which is changing the temperature of the oceans and increasing the amount of tropical storms, they may become endangered in the future.

Answers: 1. Animals Without Backbones. Coe, Wesley R. New York: Dover Publications, Inc. George, David, and Jennifer George. Marine Life. Wells, Sue, and Nick Hanna. The Greenpeace Book of Coral Reefs. New York: Sterling Co.