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Phylum Echinodermata

Phylum Echinodermata. Echinodermata. Bilateral larvae , radial adults . Body surface with five symmetrical radiating areas (ambulacra). Water-vascular system . Often with pedicellaria and Tiedemanns bodies. Endoskeleton of calcareous plates .

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Phylum Echinodermata

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  1. Phylum Echinodermata

  2. Echinodermata • Bilateral larvae, radial adults. • Body surface with five symmetrical radiating areas (ambulacra). • Water-vascular system. • Often with pedicellaria and Tiedemanns bodies. • Endoskeleton of calcareous plates. • “Mutable” connective tissue. Connective tissue can rapidly polymerize from stiff and hard to soft gel and vise versa. • Systems • Taxonomy

  3. Systems • Integumentary - thin epidermis • Skeletal - Mesodermal endoskeleton of calcareous plates (movable or fixed) • Water vascular system- derived from coelomic pouches. • Nervous - a diffused net typically of three rings centered on mouth region with radiating branches. • Excretory - isotonic, some use of amoebocytes from Tiedemann bodies.

  4. Systems continue • Respiratory- skin gills (dermal branchiae or papulae from coelom) cloacal respiratory trees in Holothuroidea. • Digestive - usually complete with anus on aboral surface. Some (Echinoidea) with mouth parts. Most use water vascular system to procure food. • Circulatory- in general no special system, use the water vascular system and the coelom. • Reproductive - Sexes usually separate, no dimorphism. Fertilization usually in the sea. Larva bilateral and usually free swimming. Many readily regenerate body parts.

  5. Echinodermata Taxonomy • Class: Crinoidea • Class: Holothuroidea • Class: Echinoidea • Class: Ophiuroidea • Class: Asteroidea • Asterias dissection

  6. Return to Taxonomy fossils Class Crinoidea • Sea lilies and feather stars • Arms branched attached by a stalk or free-moving. The mouth and anus on oral surface. No spines, madreporite or pedicellariae.

  7. Return to Taxonomy Class Holothuroidea • Sea cucumbers • Elongated body with no arms, spines, or pedicellariae. Skeleton only of microscopic plates mouth ringed by retractile tentacles(modified tube feet). Pedicellariae absent, madreporite internal.

  8. Return to Taxonomy Class Echinoidea • Sea urchins and sand dollars • Skeleton rigid (plates fused), mouth parts present, pedicellariae with 3-jaws. Spines movable. Ambulacral grooves closed. Sea urchin Sand dollar Mouth parts Sea biscuit aboral surface oral surface aboral Aristotle’s lantern endoskeleton oral

  9. Return to Taxonomy Class Ophiuroidea • Brittle stars and basket stars • Arms distinct from central disc. Ambulacral grooves closed, tube fee without suckers (not used in locomotion). Pedicellariae and anus absent. Basket star Aboral surface Oral surface

  10. Return to Taxonomy Asterias dissection Class Asteroidea • Sea stars and starfish • Arms are not sharply distinct from central disc. Ambulacral grooves open, tube feet with suckers, pedicellariae present. Aboral surface Oral surface Aboral surface Oral surface

  11. Return to Taxonomy Asterias dissection 1 Oral surface Aboral surface

  12. Return to Taxonomy Asterias dissection 2 • Aboral surface removed.

  13. Return to Taxonomy Asterias dissection 3 • Aboral surface removed.

  14. Return to Taxonomy Asterias dissection 4 • Aboral surface, stomachs and some pyloric caeca removed

  15. Return to Taxonomy Asterias dissection 5 • Aboral surface, stomachs and some pyloric caeca removed End of dissection

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