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Download Unit 6.2 - Echinodermata - Jutzi
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Unit 6.2 Phylum Echinodermata 1 Phylum Echinodermata • Radial symmetry • No head or brain – they rely on neural ganglia located in several locations to coordinate movement. • Spiny skin • Water vascular system • No excretory organs • Deuterostome • Bilateral larvae 2 Porifera Platyhelmithes Mollusca Arthropoda Cnidaria Nematoda Annelida Echinodermata Hemichordata Lophophores Chordata Protozoans 3 Class Asteroidea Sea Stars • 5 or more tapering arms • Mouth located ventrally • Exoskeleton is comprised of interlocking disks of calcium called ossicles • Tube feet allow for attachment to numerous surfaces during movement • Feed on mollusks and sea urchins 4 Class Asteroidea Aboral surface Oral surface 5 6 Aboral Surface Madreporite Madreporite 7 Oral Surface 8 Pedicellaria Spine Pedicellaria Dermal branchia • Aid in prey capture and in keeping the aboral surface clean of parasites • Located between spines on the dorsal surface 9 Pedicellaria 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Water-Vascular System of a Sea Star 11 Tube feet • Water is filtered and enters through the madreporite • Water pressure causes ampullae to extend pushing the tube foot out • Retractor muscles bend tube foot in direction of travel • Water exits back out through the madreporite and the tube foot relaxes 12 Tube foot Ampulla Lateral canal Body wall Tube foot Retractor muscles Podial muscle Sucker 13 Movement of tube feet 14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Body Wall and Internal Anatomy of a Sea Star 15 16 Feeding • Sea stars use their tube feet and their water vascular systems to attach to mollusks and pry their shells open • They may extend their stomachs externally to surround and digest prey that is too large or is otherwise inaccessible 17 Sea Stars Are Eaten Too!! 18 Reproduction • Sea stars are dioecious – separate sexes • Fertilization takes place externally • Sea stars usually gather in large groups and release their eggs and sperm into the water near each other 19 Regeneration • Many sea stars can regenerate their arms if they are lost due to predation or if they are used as decoys • Some sea stars carry most of their vital organs in their arms and can thus grow an entire new organism from just one arm 20 Regeneration Arm regenerating a body Body regenerating an arm 21 Class Ophiuroidea Brittle Stars and Basket Stars • Central disc with distinct arms like Class Asteroidea, but the similarities stop there • No pedicellariae (the little dorsal pinchers) • Tube feet lack suckers and ampullae 22 Class Ophiuroidea Brittle Stars and Basket Stars • The central disk is sharply marked off from the arms • Central disk contains all of the visceral organs • Digestive and reproductive systems do not extent into the arms like they do in Asteroidea • Tend to live in deeper waters than the sea stars as well 23 24 25 26 27 Class Echinoidea Sea Urchins • Shell (test) encloses body • Ossicles form interconnected plates that completely protect the animal • No arms • Long spines deter predators and are often coated with venom • Tube feet located between spines aid in movement 28 Sea Urchin Internal Anatomy 29 30 Class Echinoidea Sand Dollars • Burrow into the sea floor and filter out organic detritus from the sand • Madreporite is located centrally on the aboral surface • Mouth is located centrally on the oral surface 31 Class Echinoidea Sand Dollars Gonopore Madreporite Ambulacral region Lunule 32 33 Class Holothuroidea Sea Cucumbers • Soft body with reduced ossicles • Tentacles near mouth • Respiratory tree extends from the cloaca – they breath through their anus! • Able to expel a sticky, glue-like protein that dissuades predators from attack 34 35 36 Class Cridoidea Feather Stars and Sea Lilies • Most primitive of the echinoderms • Feather like arms used for suspension feeding – filter plankton from the passing water • Tube feet trap planktonic organisms • Cilia in ambulacral grooves carry food down arms to the mouth which is located on the aboral surface 37 Sea Lilies Attach to a Substrate via their Stalks 38 Feather Stars may Swim or Crawl via their Cirri 39 Central disk All the visceral organs are located in the central disk. This is similar to that of the brittle stars Mouth Anus Pinnule 40 41 The End 42
