Phylum Echinodermata Introduction

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Phylum EchinodermataIntroduction
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Echinoderms

• There are ______ characteristics of echinoderms.

five

• All echinoderms have

• Spiny skin

• An internal skeleton

• A five part body

• A water vascular system

• Tube feet

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Echinodermata Major characteristics

• secondary pentamerous radial symmetryinternal
  skeleton
• water vascular system

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• General Characteristics
• Adults exhibit pentamerous radial symmetry
• Radially symmetry is secondary larvae are
  bilaterally symmetrical and undergo metamorphosis
  to become radially symmetrical adults.

Echinoderm larva
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Water Vascular System

• Madreporite
• stone canal
• ring canal
• radial canal
• lateral canals
• Ampulae
• tube feet

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• Water Vascular System
• On the aboral surface is the opening of the
  water vascular system the madreporite (sieve
  plate)
• Water enters the madreporite and goes through
  the stone canal canal to the ring canal
• Water then passes through a radial canal
  extending into each arm
• All along the length of these canals are lateral
  canals that terminate in a bulb-like structures
  called ampullae equipped with tube feet
• Tube feet line the grooves on the oral surface -
  ambulacral grooves

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Characteristics of Echinoderms
All echinoderms have __________. Some of them
have small hair-like spines, like the starfish.
spiny skin
Some echinoderms have long spines, like the
sea urchin.
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• How the Podia Operate
• Ampulla contract and force fluid into the podia
  causing it to become extended
• Suckers at the tips of the podia come into
  contact with the substrate and adhere to the
  surface
• Then the podia contract, thereby forcing water
  back into the ampulla, and the body is pulled
  forward

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Class AsteroideaTrue Starfishes
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Asteroidea(star-like)

• starfish or sea stars belong in this class
• found all over coastal shores around the world
• prey on oysters, clams, and other sea food that
  is used by people

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Class Asteroidea True Starfishes

• arms not sharply delineated from central disc
• tube feet with suckers used for
• Locomotion
• obtaining food
• madreporite and anus aborally located
• some have pedicellariae - jawlike appendages of
  epidermis

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Class Asteroidea True Starfishes

• Feeding
• Mouth
• cardiac stomach- can be extruded
• pyloric stomach
• pyloric caecae
• Anus
• feed primarily on sessile organisms

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Class Asteroidea Systems

• Circulation
• poorly developed with fluid filled chambers
• no heart coelom ciliated for fluid movement
• Excretion
• no special organs
• general diffusion across body surfaces like tube
  feet
• Respiration
• no special organs
• across body membranes
• Nervous System
• associated with epidermis
• circular oral nerve ring with branches into arms

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Asteroidea Body wall

• Epidermis- outer surface includes
• mucous cells
• epithelium
• Pedicellariae- jawlike appendages of the
  epidermis
• can open and close
• used to clean body of debris or put debris on
  body
• Dermis- includes
• nerve cells
• connective tissue
• Skeleton- below dermis
• made of ossicles
• lattice like connections
• Calcium carbonate
• with spines and tubercles
• Muscle layer- below dermis
• Peritoneum that lines coelom

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Asteroidea Reproduction

• are dioecious external fertilization
• usually 10 gonads 2 in each arm
• have fissiparity- division of central disc into
  two animals

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Asteroidea Reproduction

• free living larvae
• bipinnaria- first larval form develops into
• brachiolaria - shows development of arms

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Class OphiuroideaBrittle Starfishes
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Ophiuroidea(snakelike)

• largest echinoderm class
• includes basket stars brittle stars
• primarily reside under stones in crevices and
  holes of coral reefs
• have thin brittle arms that break off
  regenerate themselves quickly
• feed by raking food off the ocean floor with
  their arms and bottom of tube feet
• also trap food with mucous strands between their
  spines.

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Class OphiuroideaBrittle Starfishes and Basket
Stars

• 5 arms usually
• central disc well marked off, no branches of gut
  in arms

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Class OphiuroideaBrittle Starfishes and Basket
Stars

• no anus, no ambulacral groove
• madreporite on oral surface
• no suckers on tube feet, no ampullae (have a
  valve to control pressure)
• no pedicellariae
• able to move quickly and snake like hence their
  class name

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Class Echinoideasea urchins, sea bisquits, sand
dollars
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Echinoidea(hedgehoglike)

• sand dollars sea urchins
• test rigid endoskeleton that the internal
  organs are compacted in
• Aristotles lantern complex jaw-like mechanism
  that is used to grind their food
• locomotion tube feet
• protection barbs on their long spines that are
  sometimes venomous

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Class Echinoidea

• no arms
• skeleton is fused into a solid test
• tube feet have suckers
• covered with moveable spines and pedicellariae

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Class Echinoidea
specialized mouth structures - Aristotle's
Lantern
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Class Holothuroidea Sea cucumbers
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Class Holothuroidea Sea cucumbers

• body elongated in oral-aboral axis
• skeletal system reduced or absent
• no spines or pedicellariae
• mouth and anus at opposite ends of body

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Class Holothuroidea Sea cucumbers

• no external madreporite
• tube feet with suckers
• respiration through anal respiratory tree
• dioecious single gonad
• suspension or detritus feeders
• commensal relationship with pearl fish

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Class Crinoidea Sea Lillies
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Crinoidea(lilylike)

• They include
• Sea lilies
• Feather stars
• Crinoidea are sessile
• they have long stalks that attach to rocks or to
  the ocean floor
• feather stars eventually detach themselves
• Sticky tube feet that are at the end of each arm
  catch food and serve as a respiratory surface.

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Class Crinoidea Sea Lillies

• most are extinct
• most primative
• all sessile, with stalk that attaches to
  substrate
• have branched arms for filter feeding
• no suckers on tube feet
• no madreporite
• no pedicellariae