Echinoderms are marine animals characterized by spiny skin, internal skeletons, and tube feet. They exhibit five-part radial symmetry and have a water vascular system for functions like respiration, circulation, and movement. Echinoderms reproduce through external fertilization and have larvae that swim before settling. They lack complex nervous systems but can sense their environments. Common echinoderms include sea stars, sea urchins, sand dollars, sea cucumbers, brittle stars, feather stars, and sea lilies.

1. Echinoderms

2. What is an Echinoderm? Echinoderms are characterized by spiny skin, an internal skeleton, a water vascular system, and suction-cuplike structures called Tube Feet Most echinoderms exhibit a five-part radial symmetry

3. Anatomy of Echinoderms

4. The Water Vascular System

5. The Water Vascular System (continued) The water Vascular System, which is filled with fluid, carries out many essential body functions in echinoderms Among these functions are respiration, circulation, and movement The Madreporite is the opening to the outside

6. Tube Feet A Tube Foot is a structure that operates like suction cups. Think of an Octopus, or the end of a rubber dart on a toy gun. Now, multiply that by hundreds of times to get an idea of how many a Sea Star has

7. Feeding Sea Stars are carnivorous. They wrap around bivalve animals like clams or mussels, use their tube feet to break them open, and push their own stomach out into the shell to break the clam down with its stomach enzymes

8. Feeding (continued) Other animals, like this Feather Star, are filter feeders Feather Stars stretch their tube feet and hope to catch as much plankton as they can from the sea

9. Feeding (continued) Sea Cucumbers act like the vacuum cleaners of the sea. They crawl around and eat all the algae and debris from the ocean floor Sea Urchins scrape rocks and the sea floor with their needles and eat all the algae they can find

10. Respiration and Circulation Oxygen, food processing, and waste are carried out by the Water Vascular System Sea Stars also use their Tube Feet to excrete gas and oxygen while other species use skin gills to breathe

11. Reproduction Echinoderms reproduce by external fertilization Both types of gametes are excreted into the open water where fertilization occurs Larvae can freely swim around before settling into the sea floor to mature into adults

12. Nervous System Echinoderms lack a complex Nervous System Echinoderms lack a brain, but they make up for it in a simple system of scattered nerve cells around their body which can sense light, gravity, and chemicals released by potential prey

13. Types of Echinoderms Sea Stars are the most common Echinoderms and perhaps the most famous They are slow-moving and have rough skin If torn into pieces, each piece can regenerate as long as a piece of the central part of their body is intact

14. Types of Echinoderms (continued) Like a Sea Star, only faster. Brittle Stars have longer and slender arms compared to Sea Stars Like a lizard who can shed its tail to distract a predator, Brittle Stars can shed an arm or two to escape their predators

15. Types of Echinoderms (continued) Sea Urchins and Sand Dollars are detritivores (underwater grazers) who eat algae Sea Urchins defend themselves by using their sharp needles, and Sand Dollars can burrow under sand and mud to escape their predators

16. Types of Echinoderms (continued) Sea Cucumbers are little underwater vacuum cleaners They are essential to the ecosystem since they eat all debris andorganic matter from the sea floor. Without them, swimming at sea would be like swimming in an unclean fish tank

17. Types of Echinoderms (continued) Feather Stars and Sea Lilies are among the world’s oldest living creatures They look like little Palm Trees stretching up to the sea and collect plankton with their tube feet

18. Echinoderms in Popular Media