Echinoderms: Sea Stars Goals of the lab: to introduce general characteristics of the phylum...
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Transcript of Echinoderms: Sea Stars Goals of the lab: to introduce general characteristics of the phylum...
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
Phylum Echinodermata
• eumetazoan (true tissues)
• bilaterally symmetrical larvae; radially symmetrical adults
• eucoelomate
• deuterostome
Phylum Echinodermata
Class Astroidae
Class Ophiuroidae
Class Echinoidae
Class Holothuroidae
Class Crinoidae
Sea stars Brittle stars
Crinoids
Sea urchins Sea cucumbers
Phylum Echinodermata
No circulatory system
No respiratory system
Excretion (N elimination) by diffusion
Simple nervous system, no brain
Water-vascular system
A Comparison of Early
Development in Protostomes
and Deuterostomes
Early Embryonic Development
Unfertilized egg
Starfish Development
2 blastomeres
After fertilization
& 1st cleavage
4 blastomeres
2nd cleavage
8 blastomeres
3rd cleavage
16 blastomeres
4th cleavage
32 blastomeres
6th cleavage, next slide
5th cleavage
Starfish Development (continued)
64 blastomeres
Non-motile blastula Ciliated blastula
* blastula is same size as unfertilized
egg
Gastrula: Beginning invagination
blastopore
Gastrula: During invagination
Gastrula: Archenteron, no
mesenchyme
Next slide
Starfish Development (continued)
Gastrula: Archenteron with mesenchyme
Late gastrula: lateral view
Early bipinnaria larva, lateral view
Brachiolaria larvaYoung starfish
Late bipinnaria larva, lateral view
blastopore becomes
anus
2nd opening becomes
mouth
Phylum Echinodermata
Tube feet & associated plumbing
Used for walking, clinging to substrate & holding food
Water Vascular System
Starfish water vascular system
Class Echinoidea: sea urchins
Echinometra mathaei
Colobocentrotus atratus
Echinothrix calamaris
Slate pencil urchin
Collector urchin
Class Holothuroidea: Sea Cucumbers
Holothuria atra
Polyplectana kerfersteninii
Linckia sp.
Acanthaster planci
Class Asteroidea: Sea Stars
Maui, Hawaii
Pin cushion
Class Ophiuroidea: Brittle Stars
Class Crinoidea: Feather Stars
Starfish Dissection: Schematic View
Starfish: Oral View
Mouth
Ambulacral groove
Spines
Tube feet
Starfish Dissection: Skeleton Removed: Aboral View
Stone canal
Digestive glands
Gonads
Pyloric stomach
Cardiac stomach
Starfish Arm: Digestive Glands
Removed
Ambulacral Plates
Ampullae
Cardiac Stomach
Gonads