ECHINODERMATA

• Echinoderms are Pentaradial symmetry
• Echinoderms Lack of Excretory Organs

  (diffuse through body wall or

  tube feet)
• Pedicellariae can remove debris, deter predators, and defend against parasites.
• Echinoderms have a unique hydraulic system called the water vascular system, which functions in locomotion, feeding, gas exchange, and sensory perception.
• Excretion

  ✓ Digestive waste exits the anus on opposite side of mouth.

  ✓ No distinct excretory organs – nitrogenous waste is removed from the water

  vascular system via diffusion through tube feet or with digestive waste.

  Respiration

  ✓ Use water vascular system in respiration and circulation.

  ✓ Gas exchange occurs through simple gills and diffusion through tube feet.

  Circulation

  ✓ Reduced circulatory system.

  ✓ All fluids and “blood” circle throughout the hydraulic-like water vascular

  system. Blood has no pigment (no color)

  ✓ No heart
• External fertilization

  Gametes (eggs and sperm) are released into the water (broadcast spawning) where fertilization occurs
• Echinoderms

  • Most reproduce sexually, with separate sexes and external fertilization
  • Females can release up to 100 million eggs at one time
  • Fertilized embryo develops into bilateral, planktonic larvae
  • The planktonic larvae gradually change into radially symmetrical adults under the course of two-months and settle on the ocean floor
• Asexual reproduction: Regeneration

  Due to repetition of organs in each area and a nerve disk, echinoderms can regenerate if they are fragmented with a piece of their central disk