1. Echinoderms

2. Name Echino = spiny Dermis = skin
Animals with bumpy and irregular texture

3. General Characteristics
Echinoderms have spiny skins.
Internal skeleton
They have radial symmetry (usually 5 parts)
They lack body segmentation.
Water vascular system
Tube feet = Suction cup like structures
There are more than 7000 species of Echinoderms.

4. The larvae is bilaterally symmetric They are deuterostomes
If they are radially symmetric, why are they considered a “higher” evolutionary phyla?
Echinoderms are the “highest” invertebrates  the most closely related to humans!
The larvae is bilaterally symmetric
They are deuterostomes

5. Nervous System Decentralized nervous system
Radial nerves run under the ambulacra (legs)
Central nerve ring surrounds the gut
Eyespots that can detect light
No specialized sensory organs
and no definitive brain
The arrangement of the central nervous system of echinoderms is quite different from that in other deuterostomes.
Radial nerves run under each of the ambulacra, and contain the cell bodies of almost all
motor neurons and interneurons. A central nerve ring surrounds the gut, and is composed primarily of fiber
tracks connecting the radial nerves. No known echinoderm contains anything that could be called a brain,
although ganglia are present along the radial nerves in some echinoderms. Unlike most bilaterian phyla,
echinoderms lack any trace of cephalization, and have no specialized sense organs.
Sensory neurons are located primarily within the ectoderm of podia, and send axons to the radial nerves.

6. Circulatory Structures
-A Echinoderm has water pumped through its body as part of its very simple circulation system
-no specific structures for the circulatory system
Hemal system of water pumps through the coelom.

7. Digestive/Excretory System
Tubes grab onto food -> invert their stomach -> secrete/squirt juices (enzymes) that digest -> reabsorb digested food through mouth under the center -> wastes out the aboral anus

8. Locomotion
Vascular system consist of a network of hydraulic canals branching into extensions called papullae (tube feet), which provides:
slow movement
feeding
and gas exchange
Tube feet uses hydraulics to create negative pressure which acts as a suction force.

9. SENSORY STRUCTURES -rudimentary senses including:
-light sensitive eyespots
sensory tentacles (modified tube feet) at the tips of the arms
small patches of cells sensitive to chemicals or touch.

10. Reproductive System
Most are dioecious, with separate male and female individuals, but some are hermaphrodites.
Each arm contains two gonads, which release gametes through openings called gonoducts, located on the central body between the arms.
dioecious

11. Types of Echinoderms

12. Class: Crinoidea Class: Holothuroidea Class: Echinoidea
Echinoderm Classes
Class: Crinoidea
Class: Holothuroidea
Class: Echinoidea
Class: Ophiuroidea
Class: Asteroidea

13. Class Crinoidea Sea lilies and feather stars fossils
Arms branched attached by a stalk or free-moving. The mouth and anus on oral surface. No spines. Filter feeders. Most primitive. Sedentary life, attached to substrate.
fossils

14. Class Holothuroidea Sea cucumbers
Elongated body with no arms or spines. Skeleton only of microscopic plates mouth ringed by retractile tentacles(modified tube feet). Detritus feeders. Move in herds.

15. aboral surface oral surface
Class Echinoidea
Sea urchins and sand dollars
Skeleton rigid (plates fused), mouth parts present, mouth with 3-jaws. Spines movable. Detritivores and grazers.
Sea urchin
Sand dollar
Mouth parts
Sea biscuit
aboral surface oral surface
aboral
Aristotle’s lantern
endoskeleton
oral

16. Class Ophiuroidea Basket star Aboral surface Oral surface
Brittle stars and basket stars
Arms distinct from central disc. Tube fee without suckers (not used in locomotion). Can move very fast to escape predators and can leave an arm if caught (detached arm keeps moving to distract predators)
Basket star
Aboral surface
Oral surface

17. Class Asteroidea Sea stars and starfish Aboral surface Oral surface
Arms are not sharply distinct from central disc. Tube feet with suckers (used for locomotion). Carnivores (extreme predators). Can regenerate from parts.
Aboral surface
Oral surface
Aboral surface
Oral surface

18. Life Series Time Lapse Echinoderms