KINGDOM ANIMALIA Phylum Echinodermata

1. KINGDOM ANIMALIAPhylum Echinodermata

2. Members of the Phylum Echinodermata • Date back 570 million years ago • 13,000 fossil species • Only 7,000 species today • Most are marine and benthic (90%) • Range in size (<1cm to 2 m) • 5 Classes

3. Class Crinoidea • Most ancient/primitive • 625 species • Base of 5 or 10 arms that can branch up to 200 arms • Suspension feeders • Each arm bears suckerless podia that produce mucus to capture detritus and transport it to mouth

4. Class Crinoidea • Sessile sea lily • Cup-like body attached to stalk • Attached to substrate • Can bend stalk and flex/extend arms

5. Class Crinoidea • Free-moving feather star • Stalk lost during larval development • Can crawl/swim • Jointed appendages (cirri) help it regain balance

6. Class Asteroidea • 1500 species of sea stars • 5 or more broad arms surround a central disk • Crawl on rocks or live on sea bottom • Most are scavengers or predators • Each arm bears podia with suckers • Evert stomach into prey and digest it

7. Class Ophiuroidea • 2000 species of brittle stars • Usually concealed in sand or under objects • Some live in sponges or other colonial organisms • Only 5 arms that are usually highly branched

8. Class Ophiuroidea • Arms are distinct from central disk • Can crawl/cling • Predators, scavengers, or suspension feeders • Flexible arms bear suckerless podia that secrete mucus to entrap food and transport it to mouth

9. Class Echinoidea • 1000 species of sea urchins/sand dollars • Movable spines and podia surround body; used for locomotion • Herbivorous, detrivorous, suspension feed, a few predators

10. Class Echinoidea • Unique feeding apparatus called Aristotle’s lantern • Hard plates and muscles just inside mouth • Possesses 5 calcareous teeth • Teeth protract to scrape algae off rocks or tear chunks of kelp

11. Class Holothuroidea • 1150 species of sea cucumbers • Mucus-covered oral tentacles trap on plankton or ingest sand organic matter • Gut modified to produce respiratory trees used for gas exchange • Expel portions of these trees as defense mechanism; regenerate

12. Common Body Plan • Adults are pentaradially symmetrical • 5 sets of body parts around an oral-aboral axis

13. Common Body Plan • However, larvae are bilaterally symmetrical • Settle near adults of their species and attach to substrate • Metamorphosis: left side becomes oral surface of the adult and right side becomes aboral • Larval mouth/anus disappear, gut migrates to adult position, and new mouth/anus open

14. Endoskeleton • Unique system of calcareous plates (ossicles) • Reduced in sea cucumbers • Fused to form a solid test in sea urchins/sand dollars

15. Endoskeleton • Skeletal elements bear pincer-like structures called pedicellariae • Use to rid body of debris, defense, grasp objects to hide, or capture/hold prey

16. Water-vascular system • Hydraulic system of canals and reservoirs controls the movement of tube feet (podia) • Critical to locomotion, gas exchange, feeding, and sensory reception

17. Water-vascular system • Water enters sieve plate (madreporite) • Flows from stone canal to radial canals in each arm • Lateral canals perpendicular to the radial canal terminate in muscular bulb (ampulla) connected to a tube foot

18. Water-vascular system • Water enters bulb, it contracts and water forced into foot • Extends foot, pressing terminal sucker onto substrate • Foot contracts, forcing water back into bulb and raises center of sucker • Creates a vacuum seal; only broken when bulb contracts water into foot again