1. 5-WAY SYMMETRY “spiny-skinned” movie
ECHINODERMS
5-WAY SYMMETRY
“spiny-skinned”
movie

2. ECHINODERM CHARACTERISTICS
Radially symmetrical-adults
Pentamerous – based on 5-parts
Bilaterally symmetrical- planktonic larvae
No head
No anterior/posterior end; no ventral/dorsal side
Refer to the oral and aboral side
Complete digestive tract
Well-developed coelom

3. Water-vascular system- waterfilled canals
Endoskeleton
Water-vascular system- waterfilled canals
Tube feet- muscular extensions of canals
Extended when filled with water- have muscular sacs called ampullae
Used for movement, attachment, and receiving chemical and mechanical stimuli
Madeporite- or sieve plate- in sea stars and sea urchins; on the aboral side; where water enters the water vascular system

4. BIOLOGY OF ECHINODERMS
Radial symmetry = sedentary life style
Feeding and digestion- sea stars are carnivorous; they extend their stomach out through their mouth and excrete digestive enzymes; the food is then carried into the digestive gland and the stomach moves back into the body; if intestines are present, they are very small
Brittle stars- no anus; very simple guts
Crinoids- simple guts

5. Feeding and digestion cont.
Sea urchins and sea cucumbers have long coiled guts (sea urchins need this because they are herbivores and the sea cucumbers need this because they need to process sediment)
In all echinoderms, nutrients are passed in the coelomic fluid within the coelom
Also transports oxygen because they don’t have a circulatory system
Sea cucumbers have respiratory trees- which are thin, branched tubes that are connected to the gut and extend out to the anus

6. REPRODUCTION AND LIFE HISTORY-
NERVOUS SYSTEM AND BEHAVIOR- have a nerve net- more complex actions than cnidarians though
REPRODUCTION AND LIFE HISTORY-
Separate sexes
External fertilization
Zygote develops into a ciliated larva
Some don’t have larva but brood their offspring in specialized pouches
Some reproduce asexually by the separation of the central disc or body into two pieces- REGENERATION

8. TYPES OF ECHINODERMS 7000 KNOWN SPECIES- all marine Bottom dwellers
1. Class Asteroidea= sea stars
5 arms that radiate from central disk
Amulacral groove= the radiating channels on the arms
Can move in any direction
Endoskeleton = interconnected plates of calcium carbonate creating very flexible arms; aboral surface may be covered with spines that are modified into pincer like organs called pedicellariae which helps to keep the surface clean

9. Class Ophiuroidea= brittle stars; 5 arms are very long and brittle
Asteroidea cont.
Most are predators of bivalves, snails, barnacles or other attached or slow moving animals
Class Ophiuroidea= brittle stars; 5 arms are very long and brittle
Most eat detritus and small animals
Tube feet don’t have suckers, used for feeding
No anus
Most species (2000)

10. Indian Sea Star
Anthenea crassa

11. Sunflower Sea Star
Choriaster granulatus , the dough-boy star

12. Astropectin polyacanthus
Arctic Sea Stars eating
a Clam

13. Brittle star (Ophiocoma imbricatus)
Orange-banded Brittle Star (Ophiothrix)

14. Brittle star larvae

15. CLASS ECHINOIDEA OR SEA URCHINS
Endoskeleton forms a round, rigid, shell-like test with movable spines and pedicellariae
Body forms a sphere
Mouth on bottom; anus on top
Graze on seaweeds and seagrasses
Have Aristotle’s Lantern- the set of jaws and associated muscles used by sea urchins to bite food
1000 species

16. Purple Sea Urchin with spines
Purple Sea urchin’s test w/o
spines

17. Banded Sea urchin
Pencil Sea urchin

18. Class Echinoidea cont.
Heart urchins and sand dollars have flattened bodies and short spines
They are deposit feeders using tube feet and mucus to pick up particles

19. Heart Urchin with and without spines

20. Internal Sand dollar

21. Keyhole sand dollar with and without spines

22. CLASS HOLOTHUROIDEA OR SEA CUCUMBER
Worm like
No spines and no obvious radial symmetry
Look stretched
Lies on one side where the 5 rows of tube feet are; oral and aboral surface on the ends
Endoskeleton has microscopic spicules
Deposit feeders; tube feet around mouth are modified into branced tentacles

23. Class Holothuroidea cont.
Defensive mechanisms
Secrete toxic chemicals in filament
Might expel the gut or other internal organs; this is called evisceration
Prickly red sea cucumber

24. Orange sea cucumber
Warty Sea cucumber

25. Sea cucumber eviscerating

26. CLASS CRINOIDEA OR CRINOIDS
Suspension feeders
Feathery arms
600 species of feather stars and sea lilies
Sea lilies are in deep water and attached to bottom
Feather stars perch and crawl in both shallow and deep water
An upside down brittle star with the amulacral grooves and mouth facing upward

27. Class Crinodea cont. Can have up to 200 arms
Passion flower feather star

28. Sea lily
Feather star

29. Sea lily reef