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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

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Echinoderms: Sea Stars

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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


  • bilaterally symmetrical larvae; radially symmetrical adults

  • eucoelomate

  • deuterostome

Phylum Echinodermata

  • eumetazoan (true tissues)


Phylum Echinodermata

Class Astroidae

Class

Ophiuroidae

Class

Echinoidae

Class

Holothuroidae

Sea stars

Brittle stars

Sea urchins

Sea cucumbers

Class

Crinoidae

Crinoids


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


Starfish Development

Unfertilized egg

2 blastomeres

4 blastomeres

After fertilization & 1st cleavage

2nd cleavage

6th cleavage, next slide

3rd cleavage

5th cleavage

4th cleavage

32 blastomeres

16 blastomeres

8 blastomeres


Starfish Development (continued)

64 blastomeres

Non-motile blastula

Ciliated blastula

* blastula is same size as unfertilized egg

Next slide

blastopore

Gastrula: Archenteron, no mesenchyme

Gastrula: During invagination

Gastrula: Beginning invagination


Starfish Development (continued)

Gastrula: Archenteron with mesenchyme

Early bipinnaria larva, lateral view

Late gastrula: lateral view

2nd opening becomes mouth

blastopore becomes anus

Late bipinnaria larva, lateral view

Young starfish

Brachiolaria larva


Phylum Echinodermata

Water Vascular System

Tube feet & associated plumbing

Used for walking, clinging to substrate & holding food


Starfish water vascular system


Class Echinoidea: sea urchins

Slate pencil urchin

Collector urchin

Echinometra mathaei

Echinothrix calamaris

Colobocentrotus atratus


Class Holothuroidea: Sea Cucumbers

Polyplectana kerfersteninii

Holothuria atra


Class Asteroidea: Sea Stars

Linckia sp.

Maui, Hawaii

Acanthaster planci

Pin cushion


Class Ophiuroidea: Brittle Stars


Class Crinoidea: Feather Stars


Starfish Dissection: Schematic View


Mouth

Tube feet

Ambulacral groove

Spines

Starfish: Oral View


Pyloric stomach

Stone canal

Gonads

Digestive glands

Cardiac stomach

Starfish Dissection: Skeleton Removed: Aboral View


Cardiac Stomach

Gonads

Ampullae

Ambulacral Plates

Starfish Arm: Digestive Glands Removed


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