1 Jellyfish
Transcript of 1 Jellyfish
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Chapter 9Multicellular and Tissue Levels of
Organization
Phyla Cnidaria and Ctenophora
ZoologyRick Knowles
Liberty Senior High School
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Who are the Cnidarians?
Hydra
Corals
Sea Anemones
Jellyfish
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Whats a Ctenophora?
Comb Jellies
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Phylum Cnidaria Characteristics
Radial Symmetry (or biradialsymmetry)
Diploblastic tissue-level organization
Gel-like mesoglea between epidermaland 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, outerlayer 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 betweenepidermis and gastrodermis; cells in themesoglea are from epi- or gastrodermis; not
triploblastic.
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Jellyfish Antomy Mesoglea - layer of
jelly separating twotissue layers of cup orumbrella-shaped bodyforms.
GastrovascularCavity a centralcavity that serves for
digestion, circulationand reproduction witha single opening thatfunctions as both
mouth and anus.
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Some cnidarians, such as jellies: Have elaborate gastrovascular cavities
Circular
canal
Radial canal
5 cm
Mouth
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No Bones, No Brain, but What aSting!
Cnidocytes specialized cells of cnidariansthat produce and contain stingingnematocysts; unique to Cnidarians.
Cnida (ae) a fluid-filled capsule encasing acoiled hollow tube; used for attachment,defense, and feeding.
Nematocyst a type of barbed cnida thatpenetrates 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 theanimal.
Cnidocytes on the tentacleshave trigger structures that,when touched, release the
coiled nematocyst; oftenbarbed, like a harpoon.
Contains neurotoxins toparalyze prey.
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Nemotocysts
Discharged
NemotocystFiring NemotocystNematocyst
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Dead NH Jellyfish Stings 150 ,
Hospitalizes 9
Dead Lions ManeGiant Jelly, WallisSands State Park,NH, July 22,2010
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Alternation of GenerationsMost Cnidarians have 2 Body Forms in Life
Histories:1. Polyp the sessile (attached) state in the
life cycle; cylindrical body and a mouth
surrounded by tentacles; mouth upwards;usually asexual.
2. Medusa the free-swimming stage in thelife cycle; shaped like inverted bowl; mouth
usually points downward with tentaclesdangling at margin; usually is dioecious(either male or female) and produces
gametes.; sexual.
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Alternation of GenerationsPolyp Form
attached tosubstrate at theaboral end withmouth facing
upward.Medusa Form
free swimmingwith mouthusually facingdownwardsurrounded 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 ofgases, respiration, and reproduction.
Lions mane eats another jelly
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Lions mane jellyfish eating fish
Once in GVC,gastrodermal cells
secrete digestiveenzymes andphagocytize food.
Nutritive-muscularcells contract and helpdistribute food viaperistalsis.Undigested foodleaves via the mouth,no anus.
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RespirationVia diffusion Body is only two cell
layers thick.
Jellies can be long andheavy but must bewithin 0.5 mm fromsurrounding water for
diffusion large S.A. toVolume ratio.
Use the GVC to helpwith 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 contractand push water from the GVC and outmouth polyp collapses.
Circular and radial cells may causerhythmic pulsations of bell.
May also walk along bottom withtentacles.
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Responsiveness
Most primitive nervous system in animals. Have a nerve net below epidermis carriesimpulses from local stimuli around the body.
Some touch and chemical receptorsthroughout the body. Some species have a nerve ring at the
margin of the medusa for swimming. Others have statocyst at the margin CaCo3sensitivity to gravity and coordinatesswimming.
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Sexual Reproduction
Dioecious either male or female; nothermaphrodite. Sperm or egg released into GVC or
released into water for externalfertilization.
Embryo develops into planula ciliated,free-swimming larva.
Planula attaches to substrate, becomespolyp.
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Asexual Reproduction
Polyps mayform frombudding fromother polyps.
Some usefission.
Fission in Sea Anemones
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Class Hydrozoa Small, common, marine and freshwater.
Characteristics:1. Nematocysts only in epidermis
2. Gametes are epidermal released into water andnot GVC.
3. Incomplete digestive tract with unbranched gut.4. Mesoglea is acellular; mostly thin, gel-like.
5. Polyp is dominant body from.
Most have colonial polyps that are specializedfor feeding, budding, defense. Ex. Hydra, Obelia, Gonionemus, Physalia
physalis(Portugese man-of-war)