1. Bi 212: Lecture 6
Phylum Echinodermata

2. Phylum Echinodermata: Spiny-skinned

3. Evolutionary relationships
Deuterostomes!
and HOX genes

4. Echinodermata: 4 key features
Calcareous internal skeleton
Parts: Plates, spines and pedicellariae
Why considered “internal”?
Symmetry
Bilateral symmetry (larvae)
Pentamerous radial symmetry (adults)
Water vascular system
Derived from coelom
Layout (next slide shows…)
Key function: tube foot control
Other functions
Mutable connective tissue
What does this mean?

5. Body plan: Other aspects
Perivisceral coelom
Houses organs
Gas exchange
Hydrostatic skeleton
Digestive system
Can be highly branched
Complete in some
Nervous system
No brain
Branches parallel water vascular system
Sensory (sea stars)
Eye spots
Receptors associated with tube feet
No circulatory system
No excretory system

6. Class Asteroidea: sea stars
Feeding
Stomach eversion
Enzymes
Respiration
Tube foot  ?  ?
Dermal papulae  ?
Protection
Mechanisms?

7. Class Echinoidea: Sea urchins and others
Feeding
Aristotle’s lantern
Main type of food?
Respiration
Tube foot  ?  ?
Peristomial gills  ?
Protection
Mechanisms?

8. Class Holothuroidea: Sea cucumbers
Symmetry?
Feeding
Deposit feeders (what does this mean?)
Respiration
Respiratory tree?
Water entry into tree?
Body surface ?
Tube feet ? ?
Protection
Cuvarian tubules
Evisceration…

9. Class Ophiuroidea: Brittle stars, basket stars

10. Class Crinoidea Sea lilies