Echinodermata shares the most recent ancestor with chordate, the phylum that includes people. Looking at a sea urchin, you would never think that it has more in common with humans than an octopus or a spider does. The ancestor we share was the first deuterostome animal which means that during development, the second hole that forms in the initial cell mass later becomes the mouth. As adults, echinoderms share the same basic body plan with radial symmetry and a hard endoskeleton.
Deuterostome
During development, coelomate animals go through a process called gastrulation. More information on blastula formation can be found on the Animal Characteristics Page of this website. In protostomes, the blastopore eventually develops into a mouth with the anus forming second. In deuterostomes, the blastopore eventually develops into an anus, with the mouth forming second. Echinoderms and chordates are deuterostomes.
During development, coelomate animals go through a process called gastrulation. More information on blastula formation can be found on the Animal Characteristics Page of this website. In protostomes, the blastopore eventually develops into a mouth with the anus forming second. In deuterostomes, the blastopore eventually develops into an anus, with the mouth forming second. Echinoderms and chordates are deuterostomes.
Spiny Skin
The word echinoderm roughly translates to mean "spiny skin." This is fitting since all of the members of this phylum have rough bumpy skin covered in varying types of spines.
The word echinoderm roughly translates to mean "spiny skin." This is fitting since all of the members of this phylum have rough bumpy skin covered in varying types of spines.
Water Vascular System
Echinoderms have water throughout their bodies that they use for everything from movement, to gas exchange. Water enters the water vascular system through the sieve plate or madreporite. From this opening, the water travels down the stone canal to a central ring canal and down to the arms in radial canals. From the radial canals, water can enter the ampullae which are bulbs that can push water into the tube feet. This causes the tube feet to extend or contract, and muscles in the tube feet can direct their movement. The tube feet can move the animal, grab objects and surfaces, and sense the environment. In addition to sensory tube feet, at the end of each arm, sea stars have eye spots which they can use to see light and dark but not shapes or colors.
Echinoderms have water throughout their bodies that they use for everything from movement, to gas exchange. Water enters the water vascular system through the sieve plate or madreporite. From this opening, the water travels down the stone canal to a central ring canal and down to the arms in radial canals. From the radial canals, water can enter the ampullae which are bulbs that can push water into the tube feet. This causes the tube feet to extend or contract, and muscles in the tube feet can direct their movement. The tube feet can move the animal, grab objects and surfaces, and sense the environment. In addition to sensory tube feet, at the end of each arm, sea stars have eye spots which they can use to see light and dark but not shapes or colors.
Endoskeleton
Like Chordates, Echinoderms also are characterized by a hard endoskeleton. Under their spiny skin is a layer of bony platelets called ossicles. Theses ossicles are held together by small muscles which contract and extend to move the arms of the animal. This endoskeleton provides support and protection to echinoderms.
Like Chordates, Echinoderms also are characterized by a hard endoskeleton. Under their spiny skin is a layer of bony platelets called ossicles. Theses ossicles are held together by small muscles which contract and extend to move the arms of the animal. This endoskeleton provides support and protection to echinoderms.
Asteroidea
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Crinoidea
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Ophinuroidea
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Echinoidea
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Holothuroidea
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