1. Echinoderms: Spiny-skinned animals Section 31.1

2. Animal Development  Echinoderms are related to vertebrates due to their early development  The gastrula is the early embryo – a hollow ball of cells with an opening called a blastopore  Other animals are protostomes – their mouth develops first from or near the blastopore  Echinoderms and chordates (vertebrates) are deuterostomes – their anus develops from the blastopore & their mouth develops second from another part of the gastrula

3. Development, continued…  First deuterostomes were marine echinoderms  Also the first animals to develop endoskeletons  Chordates (including all vertebrates) are deuterostomes

4. Features of Modern Echinoderms 1.Endoskeleton Calcium-rich Composed of plates called ossicles In adults the plates may fuse and hold spines that protrude through the skin 2.Five-part radial symmetry Bilateral symmetry as larvae; develop radial symmetry as adults Have no head or brain, only a central ring of nerves with branches into each arm

5. Features, continued… 3. Water-vascular system Made of interconnected canals and hollow tube feet The tube feet extend through the ossicles They are used for locomotion and feeding, as well as some gas exchange and waste excretion 4. Coelomic circulation & respiration The body cavity acts as a simple circulatory and respiratory system Skin gills may grow along the spines to increase surface area

6. Echinoderm Diversity  Sea Stars Mostly carnivores  Brittle Stars The largest class of echinoderms Have slender, branched arms Most are filter feeders  Sea Lilies and Feather Stars Most primitive echinoderms Their mouth is located on their upper surface Usually sessile

7. Sea Stars

8. Brittle Stars

9. Sea Lilies

10. Feather Star

11. Diversity, continued…  Sea Urchins and Sand Dollars Lack distinct arms Flattened bodies with protruding spines that may have poison  Sea Cucumbers Soft and slug-like Ossicles are not fused  Sea Daisies Small group, discovered in deep water

12. Sea Urchin

13. Sand Dollar

14. Sea Cucumber

15. Sea Daisy