Echinoderms

1
Echinoderms

• Chapter 28

2
Echinoderm characteristics

• Spiny skin
• Tube feet

• Water vascular system
• Usually body parts are 5x

3
Sea star wrapped around blue mussel
4
Water vascular system

• Filled with fluid
• Carries out metabolic functions respiration,
  circulation, and movement
• Madreporite opening that leads to the outside
  environment, usually forming a ring canal around
  the mouth
• Radial canal extensions in arms from ring canal
• Tube feet suckers on ends

5
 The Anatomy of a Sea Star
Section 28-4
Figure 2823
6
Feeding

• Sea urchins use 5 part jaw to scrape algae from
  rocks
• Sea lilies tube feed and arms to capture
  floating plankton
• Sea stars feed on mollusks soft tissues after
  cracking the shells open

7
Feeding on blue mussel
8
Respiration and Circulation

• Thin wall tissue of tube feet main respiration
  surface area
• Water vascular system circulation

Photo by Biomedia
9
Excretion and Response

• Digestive wastes released in feces through anus
• Nitrogenous waste ammonia, released through tube
  feet tissue and skin gills
• Lack highly developed nervous system
• Nerve ring around mouth
• Radial nerves that connect nerve ring to body
  extensions
• Scattered sensory receptors

10
Movement

• Most use tube feet.
• Movable spines attached to endoskeleton (sea
  urchins, sand dollars)
• Flexible joints (sea stars, brittle stars)
• Crawl on ocean floor (sea cucumber)

11
Reproduction

• External fertilization
• Both sperm and egg shed into open water
• Larvae swim around but develop into adults on the
  ocean floor.
• Asexual regeneration

fragmentation (breaking) of arms
12
Echinoderm groups

• Sea urchins and sand dollars
• Brittle stars
• Sea cucumbers
• Sea stars

13
Sea urchin
14
Live sand dollar
15
Dead sand dollar
16
(No Transcript)
17
Brittle star
18
Blue starfish