Echinodermata
Echinoderms, from the phylum Echinodermata, are made up of marine animals. The adults are recognized easily by their radial symmetry, which include familiar animals such as sea stars, sea urchins, sand dollars, and sea cucumbers. Echinoderms are found at all ocean depths. The phylum contains about 70,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are also the largest phylum that has no freshwater or terrestrial representatives. Echinoderms have a mesodermal skeleton composed of calcareous plates or
ossicles.The construction is a result of the growth system employed by echinoderms, adding new segments at the center of the radial limbs, therefore pushing the existing plates outwards.
ossicles.The construction is a result of the growth system employed by echinoderms, adding new segments at the center of the radial limbs, therefore pushing the existing plates outwards.
Starfish
Starfish or seastars are echinoderms belonging to the class Asteroidea. There is more than 1,700 living species of starfish that can be found in all the world's oceans, including the Atlantic, Pacific Indian as well as in the Arctic and the Southern Ocean regions. Starfish
occur across a broad depth range from the intertidal to abyssal depths.Starfish are among the most familiar of marine animals and possess a number of widely known characteristics, such as regeneration and feeding on mussels. The starfish does have an exoskeleton, meaning that it's skeleton is on the outer part of it's body. Starfish, like other echinoderms have mesodermal endoskeletons consisting of small calcareous ossicles. These calcareous ossicles are also known as "bony plates."
occur across a broad depth range from the intertidal to abyssal depths.Starfish are among the most familiar of marine animals and possess a number of widely known characteristics, such as regeneration and feeding on mussels. The starfish does have an exoskeleton, meaning that it's skeleton is on the outer part of it's body. Starfish, like other echinoderms have mesodermal endoskeletons consisting of small calcareous ossicles. These calcareous ossicles are also known as "bony plates."
Sea Urchins
Seaurchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, is round and spiny, typically from 1.2 to 3.9 inches across. Common colors include black and dull shades of green, olive, brown, purple, and red. They move slowly, feeding mostly on algae, Sea
otters, wolf eels, triggerfish, and also having other predators feed on them. The sea urchin builds its spicules, the sharp crystalline "bones" that constitute the animal’s endoskeleton, in the larval stage. The fully formed spicule is composed of a single crystal with an unusual morphology. It has no facets and within 48 hours of fertilization and finally it assumes its shape. Sea Urchins also have spines, long and sharp in some species, that protect the urchin from deadly predators. The spines inflict a painful wound when they penetrate making the urchins an undesirable meal.
otters, wolf eels, triggerfish, and also having other predators feed on them. The sea urchin builds its spicules, the sharp crystalline "bones" that constitute the animal’s endoskeleton, in the larval stage. The fully formed spicule is composed of a single crystal with an unusual morphology. It has no facets and within 48 hours of fertilization and finally it assumes its shape. Sea Urchins also have spines, long and sharp in some species, that protect the urchin from deadly predators. The spines inflict a painful wound when they penetrate making the urchins an undesirable meal.
Sand Dollar
The term sanddollar refers to species of extremely flattened, burrowing echinoids belonging to the order Clypeasteroida. Like all other members of the order Clypeasteroida sand dollars possess a rigid skeleton known as a test. The tests consist of calcium carbonate
plates arranged in a fivefold radial pattern. In living individuals the test is covered by a skin of velvet-textured spines. The spines in turn are
covered with cilia. Coordinated movements of the spines enable sand dollars to move across the ocean floor. The tests of dead individuals are often found on beaches, the textured skin missing and the skeleton bleached white by sunlight.
plates arranged in a fivefold radial pattern. In living individuals the test is covered by a skin of velvet-textured spines. The spines in turn are
covered with cilia. Coordinated movements of the spines enable sand dollars to move across the ocean floor. The tests of dead individuals are often found on beaches, the textured skin missing and the skeleton bleached white by sunlight.