Echinoderms get their name from the Latin for Spiny Skinned - Echinodermata. All Echinoderms have radial symmetry; a body construction which points outwards from the centre. This normally consists of more than 5 equal segments, each containing a set of various internal organs.
Echinoderms also have no heart, eye or blood, the function of the blood is replaced by a Water Vascular System. They also have small tentacles called Tube Feet which have suction pads situated at the extremities creating slow hydraulic controlled movement.
Some Echinoderms are planktonic feeders such as the Feather Stars, where as Sea Stars are carnivorous and even like to dine on other Sea Stars.
Echinoderms are mainly nocturnal feeders as to avoid predators which include the Triton Shell, Trigger Fish and some varieties of Crustaceans (Shrimps and Crabs).
Echinoderms have a wonderful ability to regenerate missing limbs, arms, spines and even intestines. Some Brittle stars and Sea stars can reproduce a-sexually by breaking an arm or even splitting the body in half. Each half then form into a whole new animal.
Holothuriidae Sea Cucumbers
The Holothuriidae family of approximately 185 sea cucumbers have thick fleshy bodies, ranging from small to very large, often covered with small rounded projections known as papillae. All species have many tube-like feet on the lower body and several species have 15 - 30 oral tentacles.
Stichopodidae Sea Cucumbers
Stichopodidae Sea Cucumbers have a squarish cross-section, are flat on the underside, and many members of this family are edible and harvested for restaurants. These sea cucumbers often have prominent, thick, cone-shaped projections on the body, and are found on sand or rubble close the reef edge.
Cushion Stars and Allies
The Cushion Stars and Allies contains 29 genera and 263 species of sea stars, around one sixth of the known species of sea stars. Many species within this large family are traditional sea stars, usually with 5 arms surrounding a thick, brightly coloured body with a central 'dome' which can often look as though it has been inflated.
Snake Sea Stars
The Snake Sea Stars are a large family of sea stars, named after the slender members of the genus Ophidiaster, which have snake-like arms. Many species are brightly coloured and patterned, mimicking the appearance of other marine animals which may be poisonous or dangerous for protection.
There are only two species in the Crown-of-Thorns Starfish family, the Short-Spined Crown-of-Thorns Starfish (Acanthaster brevispinus) and the Common Crown-of-Thorns Starfish (Acanthaster planci), both of which are found in the Indo-Pacific region, but only one of which, the Common Crown-of-Thorns Starfish, is usually found at the dive sites around Koh Lanta.
Toxopneustidae Sea Urchins
Toxopneustidae Sea Urchins have an internal skeleton (test) made of overlapping plates which form a globular shape. The outer shell of this family are covered with short moveable spines, with tiny pedicellariae (pincers) located between the spines. Some species have a toxic venom within these pincers which is used for defence.
Longspine Sea Urchins
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. As with other echinoderms, most Longspine Sea 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.
Temnopleuridae Sea Urchins
Temnopleuridae Sea Urchins are a family of around 66 species of spiny, spherical or globe shaped animals with hard shells which live on the seabed. As with other urchins, members of this family have five equally sized parts radiating out from their central axes. The mouth is on the underside, at the base.