1. Echinoderms: Sea Stars
Goals of the lab:
to introduce general characteristics of the phylum Echinodermata
to understand the embryological differences between protostomes and deuterostomes
to observe initial stages of embryo development, using prepared slides of starfish embryos
to examine external and internal features of the starfish, as a representative of the phylum Echinodermata

2. Phylum Echinodermata
eumetazoan (true tissues)
bilaterally symmetrical larvae; radially symmetrical adults
eucoelomate
deuterostome

3. Phylum Echinodermata Class Astroidae Class Ophiuroidae Class
Echinoidae
Class
Holothuroidae
Sea stars
Brittle stars
Sea urchins
Sea cucumbers
Class
Crinoidae
Crinoids

4. Phylum Echinodermata No circulatory system No respiratory system
Excretion (N elimination) by diffusion
Simple nervous system, no brain
Water-vascular system

5. A Comparison of Early Development in Protostomes and Deuterostomes

6. Early Embryonic Development

7. After fertilization & 1st cleavage
Starfish Development
Unfertilized egg
2 blastomeres
After fertilization & 1st cleavage
4 blastomeres
2nd cleavage
8 blastomeres
3rd cleavage
32 blastomeres
6th cleavage, next slide
5th cleavage
16 blastomeres
4th cleavage

8. Starfish Development (continued)
64 blastomeres
Non-motile blastula
Ciliated blastula
* blastula is same size as unfertilized egg
Gastrula: Beginning invagination
blastopore
Gastrula: Archenteron, no mesenchyme
Next slide
Gastrula: During invagination

9. Starfish Development (continued)
Gastrula: Archenteron with mesenchyme
Early bipinnaria larva, lateral view
Late gastrula: lateral view
Late bipinnaria larva, lateral view
blastopore becomes anus
2nd opening becomes mouth
Young starfish
Brachiolaria larva

10. Phylum Echinodermata Water Vascular System
Tube feet & associated plumbing
Used for walking, clinging to substrate & holding food

11. Starfish water vascular system

12. Class Echinoidea: sea urchins
Slate pencil urchin
Collector urchin
Echinometra mathaei
Echinothrix calamaris
Colobocentrotus atratus

13. Class Holothuroidea: Sea Cucumbers
Polyplectana kerfersteninii
Holothuria atra

14. Class Asteroidea: Sea Stars
Linckia sp.
Maui, Hawaii
Acanthaster planci
Pin cushion

15. Class Ophiuroidea: Brittle Stars

16. Class Crinoidea: Feather Stars

17. Starfish Dissection: Schematic View

18. Starfish: Oral View
Mouth
Tube feet
Ambulacral groove
Spines

19. Starfish Dissection: Skeleton Removed: Aboral View
Pyloric stomach
Stone canal
Gonads
Cardiac stomach
Digestive glands

20. Starfish Arm: Digestive Glands Removed
Cardiac Stomach
Gonads
Ampullae
Ambulacral Plates