Echino

• Phylum Echinodermata


  • Brittle Stars
  • Starfish
  • Sea Urchins
  • Sand Dollars
  • Sea Cucumbers
  • Feather Stars
• Echinoderms


  • Spiny Skin
  • 7,000 living species
  • Marine Environments
  • Shallow and deep waters
  • Vary in size (from 1cm to 1m (3feet))
  • Often brilliantly colored
• Echinoderms


  • Radial Symmetry (adult form)
  • Lack cephalization
  • Larvae are bilaterally symmetrical
• Deuterostomes


  Echinoderms are deuterostomes, which makes them different from all of the other invertebrates
• Deuterostomes


  Coelomates whose embryos have radial cleavage and anus forms near the blastopore, with mesoderm arising from outpockets of the endoderm
• Echinoderms


  • Pentaradial symmetry - the body parts extend from the center along five spokes
  • Endoskeleton composed of calcium carbonate plates
  • Many small, movable extensions of the water-vascular system called tube feet, which aid in Movement, Feeding, Respiration, Excretion
• Echinoderm Classification - Classes

  • Crinoidea
  • Asteroidea
  • Ophiuroidea
  • Echinoidea
  • Holothuroidea
• Class Crinoidea


  "lily-like" - Five arms extend from the body and branch to form many more arms, tube feet for gas exchange, cilia on arms direct food to the mouth, mouth faces up, spines absent
• Class Ophiuroidea


  "snake-tail" - Long, narrow arms help them move quickly, can break and regenerate easily, live on the ocean's floor, either rake in food with arms or trap it with their tube feet or mucus between their spines
• Class Ophiuroidea


  Star-shaped, with arms sharply demarcated from central disc, ambulacral grooves closed, covered by ossicles, tube feet without suckers and not used for locomotion
• Class Echinoidea


  "spinelike" - Test is compact, rigid endoskeleton, urchins have five teeth + their muscles = Aristotle's Lantern, spines can be sharp and contain venom, sand dollars burrow into the sand and use spines for locomotion and burrowing
• Class Echinoidea


  Globular or disc-shaped, with no arms, compact skeleton or test with closely fitting plates, movable spines, ambulacral grooves closed, tube feet often with suckers
• Class Holothuroidea


  "water polyp" - Soft bodies because the particles that make up their endoskeleton are small, use tentacles to bring food to the mouth
• Class Holothuroidea


  Cylindrical, with no arms, spines absent, microscopic ossicles embedded in muscular body wall, anus present, ambulacral grooves closed, tube feet with suckers, oral tentacles (modified tube feet), Cuverian tubules (defense)
• Class Asteroidea


  "starlike" - Live in coastal waters around the world, prey on oysters, clams, and other foods humans eat
• Class Asteroidea


  Star-shaped, with arms not sharply demarcated from the central disc, ambulacral grooves open, with tube feet on oral side, tube feet often with suckers, anus and madreporite aboral
• Sea stars


  • Typically have 5 arms, but in some species, there may be as many as 24
  • Two rows of tube feet run along the underside of each arm
• Sea stars and sea urchins

  • Pedicellariae, or little pincers, help keep the body surface free of foreign objects, including algae and small animals that might damage its soft tissues
• Gas exchange and waste excretion

  Take place by diffusion through the skin or gills
• Nervous system


  • Primitive, no brain, consists mainly of a nerve ring that circles the mouth and radial nerves that run along each arm, together they coordinate the movements of the tube feet
  • Also have a nerve net near the body surface that controls the movements of the spines, pedicellariae, and skin gills
  • Eyespot on each arm responds to light, tube feet respond to touch and chemicals
• Water-Vascular System


  • Madreporite - water enters through this small pore
  • Stone canal - connects madreporite and ring canal
  • Radial canal - extends down each arm and carries water to hundreds of hollow tube feet, has valves to ensure one way flow
• Feeding and Digestion


  • Most echinoderms are carnivores
  • A sea star captures a clam and attaches to both shells with its tube feet, eventually tiring the clam's muscles. Once the shell is opened every so slightly, the sea star ejects a portion of its stomach into the clam to digest the tissue
  • Waste is expelled through anus on aboral surface
• Reproduction


  • Most echinoderms are dioecious
  • Fertilization occurs externally after the organisms spawn
  • A free-swimming larva called a bipinnaria results and eventually develops into an adult
  • As long as a portion of the central ring remains intact, a sea star can regenerate
• Adaptive Diversification


  • Diversification of echinoderms has been limited by their most important characters: radial symmetry, water-vascular system, dermal endoskeleton
• Which Class?


  • Asteroidea
  • Ophiuroidea
  • Holothuroidea
  • Echinoidea
  • Crinoidea
• Class Crinoidea


  A class of echinoderms also known as sea lilies or feather stars, characterized by five arms that extend from the body and branch to form many more arms, tube feet for gas exchange, cilia on arms to direct food to the mouth, mouth facing up, and absence of spines.
• Five arms


  Sea lilies have five primary arms that extend from the central body (calyx).
• Tube feet


  Sea lilies have tube feet, which are used for gas exchange and movement.
• Cilia on arms


  The arms of sea lilies are covered in tiny hair-like structures called cilia, which help to direct food towards the mouth.
• Absence of spines


  Unlike some other echinoderms, sea lilies do not have spines on their bodies.
• Mouth facing up


  The mouth of a sea lily is located on the upper surface of the body, and is used to capture food particles floating in the water.