Phylum Echinodermata Echinodermata means spiny skin Habitat all
Phylum Echinodermata
• Echinodermata means “spiny skin” • Habitat: all are marine living mainly on the ocean floor. • Symmetry: Radial
• They change from a free-swimming bilaterally symmetrical larva to a bottom-dwelling adult with radial symmetry • They have an endoskeleton that is made up of calcium plates, may include protruding spines
• They have small feet called tube feet that aid in movement, feeding, respiration, & excretion. • Do not have circulatory, respiratory, or excretory systems. • They breathe through small finger-like extensions called skin gills. • Have a nervous system but no head or brain.
Reproduction • They have separate sexes. Both release their eggs or sperm into the seawater where fertilization occurs. • They develop into free-swimming larvae that grow and develop into the adult form
Diet • They eat bivalves - clams, oysters and scallops. They use the powerful suction of their tube feet to pull open the shells of their prey. • They feed by pushing their stomach out of their mouths and into the open clam. • The stomach secretes its powerful digestive enzymes right into the clam and begins digesting it while it continues to hold the shell open.
Class Asteroidea (“star-like”)
• About 1, 500 living species of starfish occur on the seabed in all the world's oceans, from the tropics to subzero polar waters • Most can regenerate damaged parts or lost arms and they can shed arms as a means of defense. • Because of this ability to digest food outside the body, starfish can hunt prey much larger than their mouths. • Their diets include clams, oysters, arthropods, and small fish.
Class Echinoidea “hedgehoglike”
Sand dollars and Sea Urchins • The skeleton is almost always made up of tightly interlocking plates that form a rigid structure called test • The mouth is provided with five hard teeth arranged in a circlet, forming an apparatus known as Aristotle’s lantern. • For protection they have barbs on their long spines that are sometimes venomous
Class Holothuroidea
• sea cucumbers, are an abundant and diverse group of worm-like and usually soft-bodied echinoderms • While support in most echinoderms is from the skeletal structure, in sea cucumbers, thick sheets of body wall muscles provide support.
Feeding • tentacles around the mouth sweep up sediment from the water
Class Crinoidea
• They include: • Sea lilies • Feather stars • Crinoidea are sessile • they have long stalks that attach to rocks or to the ocean floor • feather stars eventually detach themselves • Sticky tube feet that are at the end of each arm catch food and serve as a respiratory surface.
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