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Marine Biology. Unit IX – Phylum Echinodermata. Page 81 Phylum Echinodermata. The term “echinos” = spiny, “derma” = skin, and “ata” = group. There are approximately 6,000 extant species and about 20,000 extinct species. Characteristics of Echinoderms:
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Marine Biology Unit IX – Phylum Echinodermata
Page 81 Phylum Echinodermata The term “echinos” = spiny, “derma” = skin, and “ata” = group. There are approximately 6,000 extant species and about 20,000 extinct species. Characteristics of Echinoderms: • Free-swimming larval stage has bilateral symmetry • Adults have radial or pentamerous symmetry • No head or brain • Nervous system with a circumoral ring and radial nerves • Calcareous skeleton • Posses a water vascualr system for extending their tube feet • Locomotion by movement of tube feet, spines, or extending their arms from a central disk • Complete digestive system • Circulatory System is very reduced, called a Blood Vascular System • Respiration through tube feet, skin, and respiratory tree (in the sea cucumber) • External fertilization • Most are sexually dimorphic, some are hermaphroditic
Page 82 Phylum Echinodermata – Classes of Echinoderms Class Crinoidea - (Gr) “krinon” = lily and “zoa” = animal - Examples are Sea Lillies and Feather Stars Class Stelleroidea - (L) “stela” = star and “eidos” = form - Examples are Sea Stars, Brittle Stars, and Basket Stars Class Echinoidea - (Gr) “echinos” = spiny and “eidos” = form - Examples are Sea Urchins, Sand Dollars, and Sea Biscuits Class Holothuroidea - “holothourion” = sea cucumber and “eidos” = form - Example is the Sea Cucumber
Page 83 Phylum Echinodermata – Class Crinoidea Anatomy of a Sea Lilly Feather Star
Biodiversity of the Class Crinoidea Sea Lillies Featherstars
Page 84 Phylum Echinodermata – Class Stelleroidea North Atlantic Sea Star, Asterias rubens Marginated Sea Star, Astropecten articulatus Yellow Sea Star, Fromia polypora Sunflower Sea Star, Pycnopodia helianthoides
Page 85 “The Person and the Starfish” During a sunrise walk a person was seen dancing through the waves on the sand. Every now and then the person would bend over and pick up a starfish and toss it back into the ocean. I asked the person, “Why?” He said, “The tide is going out, if I don’t throw them back they will die.” I said, “Since there are so many starfish laying on this beach, you can’t make a difference.” Bending over picking up another starfish, the person stated, as he threw it back into the ocean, “It made a difference for that one!” Vision without action is merely a dream. Action without vision just passes the time. Vision with action can change the world.
The favorite food of sea stars are clams! They grab them with their tube feet (suction cup appendages) located on their arms and then the sea star stretches the clam apart.
The Biodiversity of Sea Stars Blue Sea Star Crown of Thorns Sea Star – responsible for the destruction of coral reefs North Atlantic Sea Star Common Sea Star
Page 86Phylum Echinodermata – Class Stelleroidea Banded Serpent Star Assorted Brittlestars Brittlestar Larva
Page 87Phylum Echinodermata – Class Stelleroidea Assorted Basket Stars
Page 88Phylum Echinodermata – Class Echinoidea The internal shell of a sea urchin is called its “test”! Purple Sea Urchin, Arbacia punctulata The Ventral View of a Sea Urchin The Dorsal View of a Sea Urchin
The Biodiversity of Sea Urchins Larval stage of a Red Urchin Planktonic stage of a Purple Sea Urchin
Page 89Phylum Echinodermata – Class Echinoidea Oral Surface of a Sand Dollar The Anatomy of a Sea Star The “doves” from the internal anatomy of a Sand Dollar. Their function is support. Aboral Surface of a Sand Dollar
Page 90Phylum Echinodermata – Class Echinoidea Sea Biscuit *Sea Biscuits are echinoderms which resemble Sand Dollars except for the fact that Sea Biscuits are much thicker than Sand Dollars.
Page 91 Phylum Echinodermata – Class Holothuroidea Dorsal and Ventral Surface of the Sea Cucumber, Cucumaria
Page 92 Phylum Echinodermata – Class Holothuroidea Internal Anatomy of the Sea Cucumber, Cucumaria