The document summarizes the five classes of echinoderms: Asteroidea (starfish), Ophiuroidea (brittle stars), Echinoidea (sea urchins and sand dollars), Holothuroidea (sea cucumbers), and Crinoidea (sea lilies). It describes the key characteristics of each class, including their anatomy, physiology, reproduction, and distinguishing features. The classes are defined by attributes such as number of arms, presence of a central disc, tube foot structure, feeding method, and whether they are sessile or mobile.

1. Phylum Echinodermata
Introduction

2. • About 6000 species, all marine
Echinodermata

3. • secondary
pentamerous radial
symmetry
internal skeleton
• water vascular
system
Echinodermata
Major characteristics

4. Water Vascular System
• Madreporite
• stone canal
• ring canal
• radial canal
• lateral canals
• Ampulae
• tube feet

5. CLASSIFICATION OF
ECHINODERMATA
• Class Asteroidea
• Class Ophiuroidea
• Class Echinoidea
• Class Holothuroidea
• Class Crinoidea

6. Class Asteroidea
True Starfishes

7. Class Asteroidea
True Starfishes• arms not sharply
delineated from
central disc
• tube feet with
suckers; used for
– Locomotion
– obtaining food
• madreporite and
anus aborally
located
• some have
pedicellariae -
jawlike appendages
of epidermis

8. • Feeding
– Mouth
– cardiac stomach-
can be extruded
– pyloric stomach
– pyloric caecae
– Anus
– feed primarily on
sessile organisms
Class Asteroidea
True Starfishes

9. • Circulation
– poorly developed with fluid filled chambers;
– no heart;
coelom ciliated for fluid movement
• Excretion
– no special organs
– general diffusion across body surfaces like tube feet
• Respiration
– no special organs
– across body membranes
• Nervous System
– associated with epidermis
– circular oral nerve ring with branches into arms
Class Asteroidea
Systems

10. • Epidermis- outer surface; includes
– mucous cells
– epithelium
– Pedicellariae- jawlike appendages of the epidermis
• can open and close
• used to clean body of debris or put debris on body
• Dermis- includes
– nerve cells
– connective tissue
• Skeleton- below dermis
– made of ossicles
– lattice like connections
– Calcium carbonate
– with spines and tubercles
• Muscle layer- below dermis
• Peritoneum that lines coelom
Asteroidea
Body wall

11. • are dioecious;
external
fertilization
• usually 10 gonads;
2 in each arm
• have fissiparity-
division of central
disc into two
animals
Asteroidea Reproduction

12. • free living larvae
• bipinnaria- first
larval form develops
into
• brachiolaria - shows
development of arms
Asteroidea Reproduction

13. Class Ophiuroidea
Brittle Starfishes

14. • 5 arms
usually
• central disc
well marked
off, no
branches of
gut in arms
Class Ophiuroidea
Brittle Starfishes and Basket Stars

15. • no anus, no
ambulacral groove
• madreporite on oral
surface
• no suckers on tube
feet, no ampullae
(have a valve to
control pressure)
• no pedicellariae
• able to move quickly
and snake like hence
their class name
Class Ophiuroidea
Brittle Starfishes and Basket Stars

16. Class Echinoidea
sea urchins, sea bisquits, sand dollars

17. • no arms
• skeleton is
fused into a
solid test
• tube feet have
suckers
• covered with
moveable
spines and
pedicellariae
Class Echinoidea

18. Class Echinoidea
specialized mouth structures - Aristotle's
Lantern

19. Class Holothuroidea
Sea cucumbers

20. • body elongated
in oral-aboral
axis
• skeletal system
reduced or
absent
• no spines or
pedicellariae
• mouth and anus
at opposite ends
of body
Class Holothuroidea
Sea cucumbers

21. • no external
madreporite
• tube feet with suckers
• respiration through
anal respiratory tree
• dioecious; single gonad
• suspension or detritus
feeders
• commensal
relationship with pearl
fish
Class Holothuroidea
Sea cucumbers

22. Class Crinoidea
Sea Lillies

23. • most are extinct
• most primative
• all sessile, with
stalk that
attaches to
substrate
• have branched
arms for filter
feeding
• no suckers on
tube feet
• no madreporite
• no pedicellariae
Class Crinoidea
Sea Lillies