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Chapter DigiDiv

BIO 2135 Chapter Notes - Chapter DigiDiv: Water Vascular System, Tube Feet, Coelom

Course Code
BIO 2135
Jon Houseman

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Phylum Echinodermata
- Marine animals
- Includes sea stars, sea urchins, brittle stars, sea cucumbers, basket stars
- Pentaradial symmetry
- Sessile suspension feeding
- Water vascular system formed from the mesocoel of the tripartite coelom
- Madreporite:
the opening of the water vascular system
- Tube feet:
hollow, fluid-filled tubes that are part of vascular system
- Muscles contract and bend to move the organism
- Sea cucumbers use a hydrostatic skeleton, brittle stars use flexible arms
- Body cavities (perivisceral cavity and water vascular system) are lined with cilia
- Excretion occurs by simple diffusion across tube feel and dermal branchiae
- Third coelomic space = hemal system
- Endoskeleton: formed from porous ossicles, fused into plates of separated and
- Complete digestive system, including digestive ceca
- Nervous system = ring that surrounds the mouth, radial nerves down the arms
- Dioecious
Class Crinoidea
- Ancient echinoderms
- Sea lilies → attached to substrate
- Feather stars → crawl across substrate
- Mouth is in the center of the upper oral surface (tegmen
- Cup-shaped calyx of calcareous plates inside
- Anus is on the oral surface, to one side at the top of the anal cone
- May have delicate arms
- Each branching arm has two rows of small lateral branches; pinnules
increase surface
- Triplets of tube feet on either side of the ambulacral groove
of the pinnule trap food
- Tube feet don’t have ampullae
- Open ambulacral grooves
- Water vascular system does not have a madreporite
- Stone canals
; seawater enters through here
- Complete gut
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