Phylum Echinodermata

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Phylum Echinodermata
ECHINODERMS!
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Class Crinoidea

• Special Characteristics Mouth Faces Upward and
  is surrounded by many arms 600 species
• Species include- Sea Lilies and Feather Stars

Florometra serratissima
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Class Asteroidea

• Body usually has five arms and double rows of
  tube feet on each arm
• Mouth faces downward
• 1,500 Species
• Ex. Sea Star
• Six-Rayed Starfish
• Leptasterias hexactis

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Class Ophiuroidea

• Usually has five slender and delicate arms or
  rays
• 2,000 Species
• Ex. Brittle Stars and Basket Stars

Daisy Brittle Star--Ophiopholis aculeata
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Class Echinoidea

• Body is Spherical, oval, or disck shaped
• Arms lacking but five part body plan is still
  seen
• 900 Species
• Ex. Sea Urchins and Sand Dollars
• Centrostephanus rodgersii

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Class Holothuroidea

• Elongated, thickened body
• Tentacles around Mouth
• 1,500 Species
• Ex. Sea Cucumbers

Thelenota rubralineata
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Evolution

• Echinoderms first evolved from a single-celled
  organism
• Popular Belief that Echinoderms evolved from
  ancestors which lived in the Pre-Cambrian and
  Cambrian Periods
• Supported by a fossils paleontologists found that
  they believe was a pre-echinoderm ancestor in the
  Pre-Cambrian period
• Other echinoderms resemble fossils of the
  Cambrian Period as well
• No Fossils found of direct Echinoderms due to the
  lack of calcium carbonate in the Echinoderms
  exoskeleton
• Echinoderms are most closely related to the
  Phylum Chordata

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Symmetry/Structural Support of an Echinoderm

• Symmetry- Echinoderms have Pentaradial symmetry
• What's Pentaradial Symmetry?
• Pentaradial Symmetry is a form of body symmetry
  where the body parts extend from the center along
  five spokes Ex. Star Fish
• Structural Support- Echinoderms have an
  endoskeleton composed of Ossicles
• Ossicles are plates composed of calcium carbonate

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Body Cavity of Echinoderms

• Body Cavity- Echinoderms have a Deuterostome body
  cavity
• That means that in the embryos of echinoderms,
  the blastopore develops into the anus, and a
  second opening in the embryo becomes the mouth

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Nutrition/Digestion

• Class Crinoidea
• Sea lilies and Feather Stars-Feed by using their
  stick tube feet, which suck small organisms from
  the water
• The organisms get filtered and get transported by
  cilia to the Crinoids' mouth which, unlike most
  echinoderms, faces up
• Class Ophiuroidea
• Basket Stars and Brittle Stars-Use their long
  arms to rake food in, such as small organisms
  from the bottom of the ocean or from Coral reefs
• Also, trap food particles with their tube feet or
  with mucous strands
• Class Echinoidea
• Sea Urchins-Use their five teeth surrounding
  their mouth to scrape algae from surfaces
• Sand Dollars- use their tube feet to capture food
  that lands on their body or swims over them

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Nutrition/Digestion Cont

• Class Holothuroidea
• Sea Cucumbers extend their tentacles, made up
  of miniature tube feet, out of their mouths and
  sweeps up food around itself
• Then it brings its tentacles inside its mouth and
  cleans the food off of them

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Nutrition/Digestion Cont

• Class Asteroidea
• Sea Stars are carnivorous and feed on mollusks,
  worms, clams, and slow moving objects
• Sea Stars, once they capture their prey extract
  their cardiac stomach which sucks the food into
  itself
• When finished the Cardiac Stomach goes back into
  the mouth and transfers the food to the Pyloric
  Stomach
• The Pyloric Stomach is connected to digestive
  glands in each arm which digest the food
  completely and absorb the nutrients

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Transportation/Circulation

• Echinoderms use the Water-Vascular System for
  Transportation
• The Water-Vascular System is a network of canals
  filled with water that connect to the tube feet
  of echinoderms and through water pressure the
  tube feet extend and contract causing the
  organism to move
• Water enters the system through small pores in
  the madreporite
• Then it heads to the stone canal, a tube that
  connects the madreporite to the ring canal, which
  goes around the mouth
• Then the Radial canal extends from the ring canal
  to the end of each arm sending water to the tubes
• Confused? Heres a Movie to show you the movement
  of the tube feet
• Circulation- All Echinoderms lack a circulatory
  system however fluid from the coelom distributes
  nutrients and oxygen to the organism

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Gas Exchange/Respiration

• Echinoderms dont posses a system of Respiration
  except the fluid from the coelem that gives the
  organism oxygen
• Gas exchange takes place by diffusion through the
  skin gills, hollow tubes that protect from the
  coelom lining to the exterior
• Some echinoderms use their tube feet to exchange
  oxygen and carbon dioxide with the water

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Water Balance/Excretion

• Echinoderms lack any main excretory systems, but
  do excrete their wastes through the thin walls of
  the tube feet
• Echinoderms use their tube feet to extract water
  and use their madreporite to take water in, which
  are part of the Water-Vascular System

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Reproduction/Development

• Most species of echinoderms are separate sexes
• Each arm that is attached to the central region
  contains a pair of ovaries or testes which
  produce eggs or sperm
• Each is released from a different echinoderm and
  fertilization occurs externally
• Each fertilized egg develops into a bipinnaria, a
  bilaterally symmetrical free-swimming larva
• After a certain amount of time, usually two
  months, the larva settles to the bottom of the
  ocean or sea and begins metamorphosis
• During Metamorphosis the larva changes from a
  bilaterally symmetrical organism to a
  pentaradially symmetrical adult

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Unique Characteristics and Facts

• Echinoderms are able to regenerate any one of
  their five appendages so long as it is attached
  to the central region
• Regeneration may take up to a year
• This can be used as a great defense mechanism
• Echinoderms have always been great souvenirs, so
  long as they have been properly dried
• Echinoderms are beloved characters of movies and
  television, most notably Patrick Star
• From SpongeBob SquarePants