Phylum Echinodermata

1. Phylum Echinodermata Sea stars, sea urchins, sea cucumbers

2. Choanoflagellates

3. General Characteristics • Echino- (spiny) derm (skin) • Exclusively Marine – usually shallow, coastal waters and ocean trenches • Unsegmented Body • Larvae are free-swimming and bilaterally symmetrical • Adults become bottom-dwelling with radial symmetry • Most have five radii or multiples of five which is known as pentaradial symmetry • Unique water vascular system

4. Larval Echinoderms with bilateral symmetry

5. General Characteristics • First phylum with endoskeleton (with exceptions) • With dermal calcium plates (calcareous ossicles) • Some with protruding spines or spicules • Complete Digestive System • No defined circulatory, respiratory, or excretory systems (no kidneys) • Instead, have tiny tube feet that aid in movement, feeding, respiration, and excretion • Distinct males and females reproduce sexually and/or asexually (Dioecious) • Have a nervous system but no head or brain.

6. Asteroidea – Sea Star

7. Class Asteroidea (“star-like”) Examples: Sea Stars Found all over coastal shores around the world Use tube feet to pry open the shells of oysters, clams, and other sea food that are used by people They also scavenge on dead crustaceans found on the ocean floor

8. Body Plan of the Sea Star Oral surface: mouth located on the underside of the body Aboral surface: top of the body (anus is located here) Ossicles: sharp protective spines made of calcium plates, covered with thin epidermal layer (this is what makes it spiny) Pedicellariae: tiny forceps that camouflage or clean the body surface (white structures)

9. External Anatomy Aboral Surface Oral Surface

10. Internal Anatomy

13. Ophiurodea – Brittle Star, Basket Star

14. Class Ophiuroidea (“snake-like”) Examples: Basket Stars & Brittle Stars Largest echinoderm class Primarily reside under stones, in crevices, and holes in coral reefs 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 Trap food with mucous strands between their spines.

15. Ophiuroidea (“snake-like”) No anus Madreporite on oral surface rather than aboral surface No suckers on tube feet, no ampullae (have a valve to control water pressure) No pedicellariae Gametes (sperm or eggs) released through bursal slits

16. Brittle star anatomy

17. Echinoidea – Sea Urchin, Sand Dollar

18. Examples: Sand Dollars and Sea Urchins Sand Dollar: Live along seacoasts & sandy areas Flat, round shape bodies Adapted for shallow burrowing Short spines allow for movement (also aid in burrowing & cleaning their bodies) Use tubes to filter food out of water Class Echinoidea (“hedgehog-like”)

19. Class Echinoidea Sea Urchins: Test: rigid endoskeleton that the internal organs are compacted in Aristotle’s lantern: complex jaw-like mechanism that is used to grind their food Tube feet allow for movement Barbs on their long spines are sometimes venomous provide protection from predators

20. Anatomy of a Sea Urchin

21. Aristotle’s Lantern – Sea Urchin

22. Holothuroidea – Sea Cucumber

23. Class Holothuroidea Example: Sea cucumbers Bodies are tough and leathery, yet still have a soft feel Skeletal system reduced or absent No hard spines or pedicellariae Feed by sweeping up sediment from the water with tentacles around mouth Protect themselves by ejecting internal organs through the anus which is also known as evisceration.

24. Sea Cucumber Anatomy

26. Crinoidea – Sea Feathers, Sea Lily

27. Class Crinoidea (“lily-like”) Examples: Sea lilies and Feather stars Sessile They have long stalks that attach to rocks or to the ocean floor Feather stars eventually detach themselves Sticky tube feet that are at the end of each arm catch food and serve as a respiratory surface.

28. Class Concentricycloidea Example: Sea Daisy

29. Class Concentricycloidea (“circular”) Examples: Sea Daisy Less than 1 cm in diameter (so extremely small) Disc-shaped with no arms Tube feet are located around the disc-shaped center Looks very much like a daisy

30. Other Structures

31. Water-Vascular System Hydrostatic pressure permits movement Path of water in the Water-Vascular System Enters the madreporite (sieve plate) Passes through stone canal Traces a path from the ring canal encircling the mouth and on to 5 radial canals that extend to each arm Ampulla: bulblike sac that each foot connects to Tube feet contract so that water enters; this allows them to be able to suction onto the surface of slippery rocks

32. Other Body Parts Fluid in coelom bathes organs to distribute nutrients & oxygen Skin gills: protect coelom lining; gases are exchanged Respiratory Trees: sea cucumbers use respiratory trees for respiration; gas exchange Nerve ring: surrounds mouth & branches off into nerve cords in each arm. Eyespots: end of each arm that responds to light

33. Reproduction Sexually reproduces with each arm producing sperm or egg Releases sperm or egg into the water for fertilization (oviparous fertilization) A fertilized egg develops into a free-swimming larvae It settles to the bottom and develops into an adult through complete metamorphosis Asexually reproduces by regenerating lost parts