Longspine Sea Urchins are a family of around 32 species of spiny, spherical, or globe shaped animals with hard shells which live on the seabed. Spotted everywhere, on all of our Koh Lanta dive trips.
As with other echinoderms, most urchins have a five part symmetry, with five equally sized parts radiating out from their central axes. The mouth is at the base, and the anus at the top.
The long spines are usually hollow, and most species have two series of spines, primary (long) and secondary (short), distributed over the surface of the body, with the shortest at the poles (top and bottom) and the longest at the equator (middle).
Like sea stars and sea cucumbers, sea urchins have small tube feet which can be used to 'walk' across the seabed, often aided by movement of their spines. An inverted Longspine Sea Urchin can right itself by using its tube feet and manipulating its spines to gradually roll its body upright.
Like other sea urchins, longspine sea urchins are sensitive to touch, chemicals and can detect light. They have eye spots which can detect light, with the spines being manipulated to allow light to fall onto the eye spots. When detecting shadows, they can flee from a perceived threat, or move toward perceived shelter.
Sea urchins feed mainly on algae, but also eat other slow moving of stationary invertebrates they may encounter. Like other families of urchins, they are eaten by sea stars and triggerfish.
Dense populations of Longspine Sea Urchins can quickly devour important marine algae communities in a coral reef ecosystem, destroying the ecosystem balance in the particular areas where these aggregations occur.
2 species found on this page.
