1. Dr Akeredolu Excellkence
Echinodermata
Dr Akeredolu Excellkence

2. Echinoderm Classes Asteroidea – Sea Stars:
Riley Galton
Echinoderm Classes
Asteroidea – Sea Stars:
Multiple arms radiating from central disk
Tube feet on bottom
Ophiuroidea – Brittle Stars:
Distinct central disk with snake like arms
Tube feet lack suckers

3. Echinoderm Classes Echinoidea – Sea Urchins and Sand Dollars:
Riley Galton
Echinoderm Classes
Echinoidea – Sea Urchins and Sand Dollars:
No arms, but 5 rows of tube feet
Have muscles that can move
spines
Crinoidea – Feather Stars and Sea Lilies
Flexible arms used in suspension feeding
Haven’t changed in 500 million years

4. Echinoderm Classes Holothuroidea – Sea Cucumbers
Riley Galton
Echinoderm Classes
Holothuroidea – Sea Cucumbers
Reduced endoskeleton
Five rows of tube feet
Concentricycloidea – Sea Daisies
Only two known species
Disk shaped, less than 1cm in diameter

5. Echinoderm Sensory Structures
Riley Galton
Echinoderm Sensory Structures
Eyespots on the ends of ambulacra are sensitive to light
Pedicellariae (jaw like skeletal structures used to keep organisms from settling on skin), tube feet, and spines are sensitive to touch

6. Echinoderm Reproduction
Riley Galton
Echinoderm Reproduction
Sexual:
Eggs and sperm are released into the water where they are fertilized
Larvae are planktonic
Internal fertilization has been observed in certain species of sea stars, brittle stars, and sea cucumbers
Asexual:
Echinoderms can regenerate body parts and organs
Asexual reproduction can occur (though not by will) if the echinoderm is torn with enough of the body on each part

7. Body Cavity (Coelom) PRESENT!
Julia Heunis
Body Cavity (Coelom)
PRESENT!
Coelom = A fluid-filled cavity between body wall and gut; lined by mesoderm
Two parts:
Perivisceral coelom – large, fluid-filled cavity where major organs, digestive tube and sex organs, are suspended
Water Vascular System - network of hydraulic canals unique to echinoderms that branches into extensions (tube feet) which function in locomotion, feeding and gas exchange

8. Body Symmetry evolved from animals with bilateral symmetry
Julia Heunis
Body Symmetry
evolved from animals with bilateral symmetry
adult echinoderms possess radial symmetry
All echinoderms exhibit fivefold radial symmetry in portions of their body at some stage of life (5 parts around central axis), even if they have secondary bilateral symmetry
For the most part…
LARVAE ~ bilateral
ADULTS ~ radial

9. Excretory System NO true excretory system!
Julia Heunis
Excretory System
NO true excretory system!
Main opening of a sponge used only to EXPEL WASTE
Anus leads directly from stomach/digestive tract
Anus = top
mouth = bottom
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10. Olivia Heunis

11. Skeletal Type Echinodermata: “Spiny Skinned”
Julia Heunis
Skeletal Type Echinodermata: “Spiny Skinned”
DO NOT possess an exoskeleton
a thin outermost skin covers a mesodermal endoskeleton made of tiny calcified plates and spines - forms rigid support contained within tissues of the organism
Skeleton composed of skeletal plates called ossicles
Ossicles = small bones
In some species, such as the sea urchin, plates of the skeleton are locked together to form a rigid structure.
most sea stars and brittle stars can flex their ‘arms’ = skeleton has gaps, flexible plate junctures

12. Other Unique Features Echinoderms can REGENERATE
Julia Heunis
Other Unique Features
Echinoderms can REGENERATE
ex: sea cucumbers can eject a portion of gut in response to predators and regenerate when safe
Water vascular system (described earlier) is unique to echinoderms; varies water pressure to control tube feet
Crinoids and some brittle stars = passive filter-feeders, absorbing suspended particles from passing water
sea urchins = grazers
sea cucumbers = deposit feeders
starfish = active hunters

13. Julia Heunis
More Unique Features
Autonomy = The spontaneous self amputation of an appendage when the organism is injured or under attack. The autotomized part is usually regenerated.
“arms” → multiples of 5; some have more because of regeneration
mutable collagenous tissue ~ connect ossicles; can maintain different positions without much effort

14. Nervous System Decentralized
David Lin
Nervous System
Decentralized
central nerve ring surrounds gut, connect radial nerves.
Radial nerves run under each arm, coordinate movement, etc.
Do not have “brains,” but some have ganglia along radial nerves

15. David Lin
Digestive System
Complete digestive system (tubular gut), mouth to anus. (bottom to top)
Crinoidia: filter-feed, use cilia
Asteroidea: Cardiac (evert), pyloric stomach, digestive glands
Urchins: “Aristotle’s lantern” (masticatory apparatus)
Holothurians: suspension/deposit feeders, use tentacles.

16. Locomotion/Musculature
David Lin
Locomotion/Musculature
Utilize water vascular system and tube feet
Water in from madreporite, pumped into ampulla by radial canal
Ampulla contracts, water to podia
Podia contracts, water to ampulla
Podia bend, shorten allows movement (vacuum and suction)

17. Gas Exchange Asteroids, crinoids: dermal gills (thin epidermis)
David Lin
Gas Exchange
Asteroids, crinoids: dermal gills (thin epidermis)
Urchins: infolds of body wall (bursae) opening to outside
Sand dollars: modified podia on top (petaloids) which are thin-walled and flaplike.
Holothurians: highly branched hindgut called "respiratory tree"

18. David Lin
Circulatory System
Mostly in perivisceral coelom, enhanced by water vascular system and hemal system.
Hemal system: series of canals and spaces mostly in coelomic channels. Fluid movement by cilia. Used to distribute nutrients. No respiratory system.

19. Quiz
Echinodermata have ________ symmetry as larvae, but display ________ symmetry as adults.
What allows Echinoderms to function in locomotion, feeding and gas exchange?
Sea stars can grow new arms and sea cucumbers can replace their gut after ejecting them. What feature of echinoderms does this demonstrate?
Name the stomachs of a sea star. Functions?

20. Answers Bilateral, radial Water vascular system Regeneration
Cardiac, pyloric; evert and enzymes, further digestion