Echinoderms copyright cmassengale

Echinoderms (Sea Stars, Brittle Stars, Sea Urchins, Sand Dollars, Sea Cucumbers, Sea Lillies and Feather Stars)

General Stuff Phylum Echinodermata: spiny skins. Echinoderms usually inhabit shallow coastal waters and ocean trenches. There are about 6,000 species of Echinoderms.

Characteristics  They lack body segmentation. Most have five radii or multiples which is known as pentaradial symmetry  Change from a free-swimming bilateral 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 copyright cmassengale

 Have small feet called tube feet that aid in movement, feeding, respiration, & excretion.  Do not have circulatory, respiratory or excretory systems.  Have a nervous system but no head or brain. Responds to stimuli.  There are two sexes and they can produce sexually and asexually. copyright cmassengale

Evolution & Classification  Echinoderms are from the Cambrian period & date back to over 500 million years ago  Scientist believe that they evolved from bilaterally symmetrical ancestor.  The inferred ancestral larva is very similar to the modern Sea star larva.  Records show that conditions have changed which had caused them to evolve from sessile organisms to free-living ones. copyright cmassengale

Taxonomists have divided 6,000 species of echinoderms into five classes copyright cmassengale

Types of Echinoderms

 Crinoidea  Asteroidea  Ophiuroidea  Echinoidea  Holothuroidea copyright cmassengale

A. Sea lilies & Feather stars (lilly-like)  Sessile - They have long stalks that attach to rocks or to the ocean floor  Nocturnal feeders with upward facing mouths  Sticky tube feet that are at the end of each arm catch food and also serve as a respiratory surface.

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B. Sea stars (star-like)  Found all over coastal shores around the world copyright cmassengale

Sea Stars Have radial symmetry. Most starfish have 5 “arms”or rays. Starfish have tube feet for locomotion, and strong suction to hold them in place. They also have a water vascular system that enables them to store water in their tube feet so they can survive while the tide is out. They breathe through small gills in their skin. Their mouths are located on the underside of their bodies. Starfish can regenerate. (must have the central disc attached).

More Starfish Stuff Sea Stars are carnivorous, yup, they eat mostly shellfish, snails, and barnacles. They use their tube feet to pry open the shells and then throw their own stomachs out into the shell to digest the meat before it’s brought back into its body! There are lots of different types of Sea Stars, about 2000 different kinds. Most Sea Stars have spiny skin.

Sea Star Anatomy

Structure & Function copyright cmassengale

Body Plan of the Sea Star  oral surface: mouth located on the underside of the body  aboral surface: top of the body  ossicles: sharp protective spines made of calcium plates, covered with thin epidermal layer  pedicellariae: tiny forceps that protect and clean the body surface copyright cmassengale

Water-Vascular System  hydrostatic pressure permits movement  Path of water in the Water-Vascular System u enters sieve plate u passes through stone canal u traces a path from the ring canal encircling mouth to 5 radial canals that extend to each arm copyright cmassengale

Water vascular system Fluid-filled canals that lead to tube feet Sea star: madreporite, stone canal, ring canal, radial canal, ampulla, tube feet

 ampulla: bulblike sac that each foot connects to  feet contract, water enters and are able to suction onto surface of slippery rocks copyright cmassengale

Feeding & Digestion  uses feet  eat mollusks, worms, and slow-moving animals  enzymes help digest food copyright cmassengale

Other Body Parts  fluid in coelom bathes organs & distributes nutrients & oxygen  skin gills: protect coelom lining; gases are exchanged  nerve ring: surrounds mouth & branches off into nerve cords in each arm.  Eyespots: on each arm that responds to light  tentacles: responds to touch copyright cmassengale

Reproduction   each arm produces sperm & egg  sexual reproduction occurs externally  bipinnaria: free-swimming larva that a fertilized egg develops into  settles in the bottom and develops into an adult through metamorphosis  reproduce asexually by regenerating lost parts copyright cmassengale

(“snakelike”) C. Basket stars & Brittle stars (“snakelike”)  largest echinoderm class  primarily reside under stones & in crevices and holes of coral reefs  have thin brittle arms that break off & regenerate themselves quickly  feed by raking food off the ocean floor with their arms and bottom of tube feet  also trap food with mucous strands between their spines. copyright cmassengale

(“hedgehoglike”) D. Sand dollars & Sea urchins (“hedgehoglike”)  Internal organs are compacted in rigid endoskeleton  Aristotle’s lantern: complex jaw-like mechanism that is used to grind their food  No arms  Locomotion: tube feet and use spines

1. Sea Urchins Sea urchins look like big pin cushions. They use these spines for protection against predators. They eat mostly algae. Important role in marine ecosystem - Help control algae growth They live mostly attached to rocky crevices, which protect them from waves and tide surges. They have become a popular item to eat and are being harvested in alarming numbers.

Sea Urchin Anatomy

2. Sand dollars  live along seacoasts & sandy areas,  Thin & flat; an adaptation for shallow burrowing  locomotion: short spines (also aid in burrowing & cleaning their bodies)  use tubes to filter food out of water

Sand Dollars They feed standing on edge with their tube feet acting as filters. The star pattern seen on top of the sand dollars is actually caused by special breathing tube feet! The mouth is found on the under side of the animal.

Sand Dollar Anatomy

Sea Cucumbers Sea cucumbers have tentacles at their mouth openings to grab and hold food. They look like snails (soft bodied) but have radial symmetry and spiny bodies like all other echinoderms. When provoked, or annoyed, Sea cucumbers throw out their intestines to entangle, frighten, or confuse their predator! Then the intestines are regenerated. They are filter feeders and have a sticky slime that covers their tentacles and lets them grab particles from the ocean floor. Sea Cucumbers are considered a delicacy in Asian cultures.

Sea Cucumber Anatomy

Interesting Stuff Some Sea cucumbers are quite poisonous, and the poison has been used as an inhibitor of Cancer growth. Sea Cucumbers secrete a sticky glue as a defense mechanism that has been used as a bandage to bind wounds. Sea Cucumbers will stick each tentacle in their mouths, lick them off and then do the same with the next one- kind of like you licking your fingers after eating!