Echinoderms are marine invertebrates with a pentaradial symmetry as adults and a water vascular system. They include sea stars, sea urchins, sand dollars, brittle stars, sea cucumbers, and sea lilies. The document describes the key characteristics, anatomy, lifecycles, and functions of the five classes of echinoderms.

2. • Spiny skin.
• sea-star, sea-urchins, sea-cucumbers, sand
dollars, sea-lilies.
• Larval stage bilateral.
• Adult stage Pentaradial.
• Arms are movable appendages radiating
around central disk.

3. Larva with bilateral symmetry Adult with radial symmetry

4. Skeleton:
• Internal
• Mesodermal in origin.
• Consist ossicles covered by epidermis.
• Ossicles enclosing other tissues in flexible and
tough covering.

5. Water Vascular System
• Contains series of water filled canals which are
connected to tube feet.
• Main elements of water vascular system.
1.Ring canal.
2.Radial canals.
3.Lateral canals.
4.Madreporite.
5.Tube feet.
6.Hemal system.

6. • Ring canal have
1.Tiedmann Bodies produce coelomocytes.
2.Polian Vesicles a fluid storage sac.
• Canal system ends in to tube feet.
• Tube feet are for feeding locomotion,
respiration.
• Valves and suction cups present in tube feet.
• Hemal system strand of tissues, it transport
large molecules, hormones and coelomocytes.

9. Functions of Water Vascular System
Water vascular system perform many functions
in echinoderms like:
• Locomotion.
• Respiration.
• Attachment.
• Feeding.
• Exchange to environment.

10. • No excretory organs.
• No respiratory system.
• No well developed head.
• Poorly developed brain.
• Complete digestive tract.
• Ability to regenerate.
• Reproduced asexually and sexually.

11. Phylum echinodermata is divided into five
classes:
1. Class Asteroidea (sea stars).
2. Class Ophiuroidea (brittle star).
3. Class Echinoidea (sea urchin).
4. Class Holothuroidea (sea cucumber).
5. Class Crinoidea (sea lilies, feather stars).

12. Class Asteroidea
• Common member sea-stars.
• Mostly marine, may live in sandy/muddy area.
• Pentagonal/star-shaped body plan.
• Large coelome.
• Oral surface oriented downward.
• Aboral surface directed upward.

14. • Ossicles provide skeletal support.
• Between ossicles dermal branchiae present for gas
exchange.
• Pedicellariae is organ of defense.
• Ambulacral groove to capture food.
• Five groove present, one on each arm.
• Move in stepping motion.
• All feet move in one direction, under the control of
nervous system.
• Suction cups will maintain the position of animals.

15. • Sea stars feed on snails, crustaceans, corals.
• Complete gut system.
Stomach divided into two parts:
1. Large cardiac stomach.
2. Smaller pyloric stomach.
• Pyloric cecae helps in digestion.
• Gas exchange, nutrients metabolic waste transported
in coelome by ciliary movement of body cavity.
• Nerve ring and radial nerve present.
• Sensory receptors are on the body surface.
• They respond to light, chemicals, mechanical stimuli.

16. • Sea stars can reproduced asexually by
regeneration.
• Sexually,they are dioecious.
• External fertilization.
• Fertilized egg first develop into bipinnaria
larva.
• Then brachiolaria larva form with
development of arms.
• Larva are bilateral.
• Have bands of cilia for swimming.

17. • Larva undergoes metamorphosis and grows
into adult.
• Left side of larva become oral surface of adult,
and faces down.
• Right side become aboral surface, faces
upward.
• Larva settled to sea floor.
• Adapt adult radial symmetry.

19. Sea Daisy
• Unusual group.
• Tiny animals.
• Upper surface made of scales lined by spines.
• Lacks arms.
• No internal digestive system.
• Thin membrane Velum cover the outer surface,
through which nutrients absorbed & digested.
• Internal pouch to hold embryo during development.
• Free swimming larval stage absent.

20. Sea Daisy

21. Class Ophiuroidea
• Include basket star, brittle star.
• All are marine.
• Brittle stars have unbranched arms.
• Basket stars have branched arms.
• Dermal branches, pedicellariae absent.
• Tube feet lacks suction cups.
• Madreporite present on oral surface.
• Arms & tube feet used to sweep food to mouth.

22. • Mouth located in centre and surrounded by
five jaws for chewing.
• Mouth lead to stomach.
• No other digestive part extended into arms.
• Reduced coelome.
• Ammonia is primary waste product.

24. Basket Star

25. Class Echinoidea
• Includes sea-urchins, sand dollars, heart
urchins.
• May be round/heart shaped/flat.
• Body of sea-urchin covered by rigid shell
called test.
• Test is made of interlocking plates of calcium
carbonate.
• Test is lined by spines.

26. Sea urchin
Heart urchin
Sand dollar

27. • Spines are sharp, hollow, contain venom.
• Pedicellariae may contain venom sac, injected
into predators.
• Water vascular system similar to others.
• Tube feet has suction cups.
• Echinoids move by using tube feet and spines.
• Special chewing organ is Aristotle’s Lantern.
• It is feeding organ consisting of 35 ossicles
and muscles.

30. • Large coelome present.
• Small gills present.
• Gas exchange through gills.
• They are dioecious.
• Coelome filled with gametes during breeding
season.
• Fertilization external.
• Early development lead to larval stage.
• Larva undergo metamorphosis and develop
into adult.

31. Class Holothuroidea
• They are sea cucumber.
• Arms absent.
• Tube feet modified into tentacles.
• Body wall thick, lacks spines and pedicellaries.
• Ossicles embedded in dermis.
• Ossicles may be microscopic or large.
• Large ossicles form calcareous ring around oral end
of digestive tract.
• Ring serve as attachment organ.
• Madreporite is internal.

33. • Water vascular system filled with coelomic fluid.
• Ring canal, radial canal lateral canals and an
additional canals for tentacles.
• Tube feet have suction cups.
• Three rows of tube feet used for attachment.
• Two other rows are reduced/absent.

35. Sea cucumber

36. Class Crionoidea
• Sea lilies with long stalk.
• Unattached end is Crown.
• Aboral end of crown has calyx.
• Five arms attached to calyx.
• Arms are branched giving feather like
appearance.

38. • Arms supported by ossicles.
• Tube feet present along each arm.
• Feather-star lack stalk.
• They have cirri for attachment.
• Gas exchange & excretion similar to
echinoderms.
• Trap prey by tube feet.
• Nerve ring absent.

41. • Cup-shaped nervous mass below calyx, which
give radial nerve, that control the movement of
tube feet.
• Dioecious/monoecious.
• External fertilization.
• Metamorphosis occurs.
• Larval stage develop to adult stage.
• They reproduced asexually by regeneration