Chapter 9 Multicellular and Tissue Levels of Organization

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Chapter 9 Multicellular and Tissue Levels of
Organization

• Phyla Cnidaria and Ctenophora
• Zoology
• Liberty Senior High School

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Who are the Cnidarians?
Hydra
Sea Anemones
Corals
Jellyfish
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Whats a Ctenophora?
Comb Jellies
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Phylum Cnidaria Characteristics

• Radial Symmetry (or biradial symmetry)
• Diploblastic tissue-level organization
• Gel-like mesoglea between epidermal and
  gastrodermal tissue layers
• Gastrovascular Cavity
• Nerve net for a nervous system
• Have cnidocytes specialized cells used in
  defense and feeding

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Radial Symmetry
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Diploblastic Tissue Level

• Ectoderm becomes the epidermis, outer layer of
  body wall.
• Endoderm becomes gastrodermis, inner layer of
  body wall.
• Epidermis and Gastrodermis can become many other
  cell types.
• Mesoglea is a jellylike layer between epidermis
  and gastrodermis cells in the mesoglea are from
  epi- or gastrodermis not triploblastic.

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Jellyfish Antomy

• Mesoglea - layer of jelly separating two tissue
  layers of cup or umbrella-shaped body forms.
• Gastrovascular Cavity a central cavity that
  serves for digestion, circulation and
  reproduction with a single opening that functions
  as both mouth and anus.

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• Some cnidarians, such as jellies
• Have elaborate gastrovascular cavities

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No Bones, No Brain, but What a Sting!

• Cnidocytes specialized cells of cnidarians that
  produce and contain stinging nematocysts unique
  to Cnidarians.
• Cnida (ae) a fluid-filled capsule encasing a
  coiled hollow tube used for attachment, defense,
  and feeding.
• Nematocyst a type of barbed cnida that
  penetrates prey often delivers toxins.

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Cnidarian Tentacles

• Tentacles may have several kinds of cnidae.
• Some cnidae produce mucus to entrap prey or
  anchor the animal.
• Cnidocytes on the tentacles have trigger
  structures that, when touched, release the coiled
  nematocyst often barbed, like a harpoon.
• Contains neurotoxins to paralyze prey.

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Nemotocysts
Discharged Nemotocyst
Firing Nemotocyst
Nematocyst
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Dead NH Jellyfish Stings 150 , Hospitalizes 9
Dead Lions Mane Giant Jelly, Wallis Sands State
Park, NH, July 22, 2010
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Alternation of Generations

• Most Cnidarians have 2 Body Forms in Life
  Histories
• Polyp the sessile (attached) state in the life
  cycle cylindrical body and a mouth surrounded by
  tentacles mouth upwards usually asexual.
• Medusa the free-swimming stage in the life
  cycle shaped like inverted bowl mouth usually
  points downward with tentacles dangling at
  margin usually is dioecious (either male or
  female) and produces gametes. sexual.

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Alternation of Generations

• Polyp Form attached to substrate at the aboral
  end with mouth facing upward.
• Medusa Form free swimming with mouth usually
  facing downward surrounded by feeding tentacles.

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Typical Jellyfish Life Cycle
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Feeding and Digestion

• Carnivorous eat plankton, small crustaceans,
  fish, EACH OTHER!
• Tentacles snag prey and drag to mouth.
• Gastrodermis lines gastrovascular cavity (GVC)
  functions in digestion, exchange of gases,
  respiration, and reproduction.

Lions mane eats another jelly
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Lions mane jellyfish eating fish

• Once in GVC, gastrodermal cells secrete
  digestive enzymes and phagocytize food.
• Nutritive-muscular cells contract and help
  distribute food via peristalsis.
• Undigested food leaves via the mouth, no anus.

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Respiration

• Via diffusion
• Body is only two cell layers thick.
• Jellies can be long and heavy but must be within
  0.5 mm from surrounding water for diffusion large
  S.A. to Volume ratio.
• Use the GVC to help with this.

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Internal Transport

• Via diffusion

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Excretion

• Via diffusion

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Movement

• Buoyancy from water also hydrostatic skeleton
  from the GVC.
• Move on water current or wind.
• Epithelial cells in body wall can contract and
  push water from the GVC and out mouth polyp
  collapses.
• Circular and radial cells may cause rhythmic
  pulsations of bell.
• May also walk along bottom with tentacles.

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Responsiveness

• Most primitive nervous system in animals.
• Have a nerve net below epidermis carries
  impulses from local stimuli around the body.
• Some touch and chemical receptors throughout the
  body.
• Some species have a nerve ring at the margin of
  the medusa for swimming.
• Others have statocyst at the margin CaCo3
  sensitivity to gravity and coordinates swimming.

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Sexual Reproduction

• Dioecious either male or female not
  hermaphrodite.
• Sperm or egg released into GVC or released into
  water for external fertilization.
• Embryo develops into planula ciliated,
  free-swimming larva.
• Planula attaches to substrate, becomes polyp.

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Asexual Reproduction

• Polyps may form from budding from other polyps.
• Some use fission.

Fission in Sea Anemones
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Class Hydrozoa

• Small, common, marine and freshwater.
• Characteristics
• Nematocysts only in epidermis
• Gametes are epidermal released into water and
  not GVC.
• Incomplete digestive tract with unbranched gut.
• Mesoglea is acellular mostly thin, gel-like.
• Polyp is dominant body from.
• Most have colonial polyps that are specialized
  for feeding, budding, defense.
• Ex. Hydra, Obelia, Gonionemus, Physalia physalis
  (Portugese man-of-war)

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Hydrozoan Life Cycle
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Hydra

• Freshwater hydrozoan that lacks a medusa stage.
• Asexually reproduces by budding from the side of
  polyp. Sexual reproduction occurs in polyp stage.

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Hydra Anatomy
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Brown Hydra Budding
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Brown Hydra eating
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Hydra Capturing Daphnia
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Order Siphonophora

• Large colonies of specialized polypoid and
  medusoid individuals.
• Various medusoid individuals form swim bell, sac
  floats, defensive structures, etc.
• Many represent a bridge between colonial animals
  and complex organisms
• Exist as colonies
• Within colonies are special polyps adapted to
  feeding, reproduction, movement, and other
  functions
• Major predators with some consuming significant
  quantities of krill
• Example Portuguese man-of-war

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Physalia physalis , Portuguese man of war(a
Hydrozoan), NOT a true jellyfish
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Man of war colony of specialized medusoid
and polypoid organisms efficient predator of
krill.
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Class Scyphozoa True Jellyfish
Fried egg jelly
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Class Scyphozoa

• All marine, mostly harmless, true jellyfish
• Characteristics
• Dominant stage is medusa form.
• Mesoglea is thicker with some amoeboid cells.
• Incomplete digestive tract with four branches.
• Cnidocytes in gastrodermis and epidermis.
• Gametes are gastrodermal in origin.
• Ex. Aurelia, Mastigias (Stinging nettle)

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Class Scyphozoa

• Range in size from smaller than a coin to more
  than a meter across with tentacles more than 3 m
  long
• Most are large planktonic organisms that swim but
  also drift with the current
• Weak swimmers, move by contracting their rounded
  body, or bell
• Feed on almost anything they catch
• Dangerous species helmet shaped bells, with
  long tentacles and fleshy lobes from oral surface.

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Scyphozoan Life Cycle
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Ecological Role of Scyphozoans

• Efficient predators of plankton, crustraceans,
  fish, etc.
• Prey for leatherback turtle and several species
  of large fishpredators move seasonally with
  jellies.
• Plastic bags, balloons, and small trash often are
  mistaken by turtles as jellies and can harm them
  by obstructing their digestive tracts.

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True Jellyfish
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Red-eyed medusa
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Jellyfish at TCI
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True Jellyfish
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Jellyfish
Lions mane
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Jellyfish
Purple lions mane
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Jellyfish that break the rules Upside Down
Jellyfish
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Sea Nettle
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Could jellyfish ever be a problem?
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Giant Jelly off Coast of Japan
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When Jellyfish are a Problem!
http//abcnews.go.com/video/playerIndex?id9226474

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Cyanea capillata 7 ft. bell, 120 ft tentacles
one of the largest
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Jellyfish Humor
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Class Cubozoa

• Medusa is cuboidal, tentacles hang from each
  corner.
• Polyps are very small
• Active swimmers and feeders in warm tropical
  waters.
• Ex. Sea wasp, box jellies.

Irukandji or Carukia barnesi
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Class Cubozoa Box Jellyfish
Chironex fleckeri
Irukandji or Carukia barnesi
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Chironex fleckerithe sea wasp
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Portuguese Man o War vs. Box Jelly fish
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Class Anthozoa

• All marine, colonial (corals) or solitary (sea
  anemones)
• Characteristics
• Lack a medusa stage.
• Cnidocytes have no cnidocils (triggers).
• Mouth leads to a pharynx and then to the GVC.
• GVC is divided by mesentaries that bear
  cnidocytes and gonads.
• Mesoglea have amoeboid cells
• Ex. Corals and sea anemones

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Sea Anemones

• Mostly solitary and colorful
• Sessile attach to surfaces with a pedal disk
  may burrow or glide on disk. If threatened, may
  force water out GVC and fold over for protection.

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Sea Anemones

• Have a hydrostatic skeleton in GVC and mesentary
  compartments.
• Muscle fibers are gastrodermal.
• May crawl on sides or thrash about, when
  threatened.
• Feed on invertebrates and fish.

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Anemone Reproduction

• Asexual (fragmentation or fission) and sexual
  reproduction monoecious or dioecious.
• If monoecious, male gametes mature earlier than
  female gametes to avoid self-fertilization
  protandry.
• Gametes mature along mesentaries and
  fertilization is either external or within the
  GVC.

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Rosy Sea Anemone
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Anemone Symbiosis

• Found in tropical waters, clown anemonefish
  (e.g. clownfish) receive protection by living
  among the stinging tentacles.
• Has protective mucous and becomes acclimated to
  toxin by rubbing its sides on anemone.
• Fish eats parasites and fans water for anemone
  fish is also protandry Finding Nemo is wrong!
  Dad should become Mom!

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Clown anemonefish eggs with sea anemone
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The Other Anthozoan - Corals

• Stony corals form reefs
• Epithelial cells secrete calcium carbonate
  exoskeleton around base and sides of column.
• When threatened, polyps retract into exoskeleton.
• Reproduction similar to anemone, asexual budding
  produces colonies.

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Coral Life Cycle
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Class Anthozoa Corals
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Brain Coral
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Coral
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Sea Fan
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Flower Coral Coral with Exposed Polyps
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Coral Symbiosis

• Living in epidermis or gastrodermis are algae
  zooanthellae.
• Photosynthetic dinoflaellate zooxanthellae
  provide sugars and other organics for the coral
  (up to 98 of the food for corals).
• Metabolism of coral polyps provide the algae with
  nitrogen and phosphorus.
• Zooxanthellae remove CO2 from water, the pH
  raises and the calcium carbonate precipitates as
  aragonite (exoskeleton for coral polyps.
• Thus, corals must live in warm shallow (less than
  90 m) of water for photosynthesis.

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Zooanthellae Living inside Coral Polyps
Responsible for the bright colors of corals
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Corals with an Attitude!

• Fire Coralscreate a mild burn upon contact
• Waxy, tan appearance and grow in small tree-like
  colonies or as an encrusting colony on an
  existing reef

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Phylum Ctenophora

• Ctenophora comb bearers comb jellies and sea
  walnuts all marine.
• Characteristics
• Diploblastic maybe triploblastic (cellular
  mesoglea)
• Biradial symmetry
• Gel and cellular mesoglea
• True muscle development in mesoglea
• GVC
• Nerve net
• Adhesive structures called colloblasts
• Eight rows of ciliary bands comb rows for
  locomotion

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Ctenophorans

• Comb rows coordinated via statocyst at the aboral
  pole.
• Colloblasts are adhesive cells used to capture
  prey.
• Tentacles bring food to mouth that leads to
  branched GVC.
• Has two anal canals have an anal opening
  (unlike jellies)
• All are monoecious both male and female sex
  organs in same individual.

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Comb Jellies use Rows of Cilia to Move Some are
Bioluminescent