most common type of brittle star is the long-armed type, which is a grayish or bluish species that is luminescent. Brittle stars with many branched arms are called basket stars. Some brittle stars may reproduce by breaking across the middle of the body disk, with each of the halves growing it’s missing half and corresponding arms. Brittle stars lack open groves on the lower surface of their arms. Each arm contains a series of jointed bonelike plates, or ossicles, which determine the freedom of arm movements. They can move in any direction and very quickly. They also have a skeleton composed of numerous plates of calcium carbonate.2.1 StereomThe plates that compose brittle starfish, ophiuroids and echinoderms is calcite along with other organics. Though each plate is a single crystal of calcite, it doesn’t take a typical crystalline form. Below is a picture of the tooth socket, notice the holes. 2.2 Water Vascular SystemPerhaps not as obvious is the water vascular system, another trait common to all echinoderms. By examining the oral underside side of a brittle star, one will be able to see hundreds of tiny feet usually arranged into several rows on each appendage of the star. These are the tube feet, or podia, and are filled with seawater in brittle stars. The water vascular system within the body of this species is also filled with seawater. By expanding and contracting chambers within the water vascular system, the brittle star can force water into certain tube feet to extend them. The animal has muscles in the tube feet, which are used to retract them. By expanding and retracting the right tube feet in the proper order, the creature can walk. Many echinoderms can also form suckers on the ends of their tube feet. These suckers can be used to capture and hold prey, or to hold onto rocks in a swift current or tide. 3.0 HabitatBrittle stars can be found in the warmest and coldest of the world’s seas and have a broad geo...
