Parazoa and Radiata

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Parazoa and Radiata

• Sponges
• Cnidarians
• Ctenophores

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Phylum Porifera The Sponges
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General Information

• Mainly marine organisms
• May have algae or bacteria that give them color
• Function much like choanoflagellates
• Larva are flagellated, adults considered sessile

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Tube Sponges
Encrusting Sponges
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Characteristics

• Filter feeders / suspension feeders
• Can reproduce sexually or asexually
• Gas exchange and excretion - diffusion at
  individual cells

• Simple animals made of few specialized cells
• NO tissues
• Asymmetrical
• Body with ostia

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Sponge Parts

• Ostia pores, allow water to enter and circulate
• Formed by porocytes
• Spongocoel central cavity
• Osculum large opening at top of sponge where
  water leaves
• Mesohyl, supported by spicules

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Sponge Parts, cont.

• Amoeboid cells (aka wandering cells)
• Secrete spicules and spongin
• Digestion, transport of nutrients
• Develop into gametes
• Choanocytes (collar cells) line inner cavity of
  sponge have flagella to move water through sponge

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Movement through a Sponge
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Sponge Suspension feeding

• Flagella of choanocyte creates current to move
  water in
• Collar cells trap food and it is digested
  (phagocytosis)
• Some food is transferred to amoeboid cells for
  digestion and transfer to epidermis
• Undigested food leaves through osculum

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Sponge Reproduction

• Asexual reproduction bud may break off and
  become new sponge
• Sexually most sponges are hermaphrodites
• Amoeboid cells become egg/sperm
• Sperm released into water
• Fertilization occurs in mesohyl
• Zygote becomes flagellated larva that leaves in
  flow of water

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Phylum Cnidaria
Jellyfish
Box jelly
Sea anemone
Coral
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Main Characteristics

• Diploblastic, radial symmetry
• Cnidocytes with nematocysts concentrated in
  tentacles
• Gastrovascular cavity with 1 opening
• Gas exchange and excretion occur by diffusion

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Discharging of Nematocysts
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Body Structure

• Epidermis protection
• Gastrodermis - digestion
• 2 layers separated by mesoglea

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Structure cont

• Nerve nets
• Connect sensory cells to contractile cells
• Sense organs around edge of body
• Ex. photoreceptors
• Contractile cells
• Not true muscles
• Act as hydrostatic skeleton

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Cnidarians come in 2 forms

• Medusa tentacles down

• Polyp tentacles up

• Many alternate between medusa and polyp
  during life cycle

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4 Classes of Cnidaria

• Hydrozoa Scyphozoa Cuboza Anthozoa

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Cnidarians are Carnivores

• Sting prey with their tentacles
• Push food into their mouth
• Digest food in gastrovascular cavity
• Waste leaves through mouth
• Jellyfish.asf

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A word about corals

• Many have symbiotic relationship with
  zooxanthellae
• Dinoflagellate
• Give coral its color
• During unfavorable conditions, algae may leave
  causing coral bleaching
• Pollution
• Warm temp.
• UV radiation

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Interesting Facts

• Portuguese Man-of-War
• Colonial
• Has sail-like float
• Tentacles can grow up to 165 feet and are nearly
  invisible
• Stings are very painful, like hot charcoal
• Allergic reactions may cause shock or death

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More interesting facts

• Box Jellies
• More toxic than Man-of-War
• Stings can lead to heart failure within minutes
• Difficult to see
• Tentacles may reach 15 feet

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CTENOPHORA THE COMB JELLIES

• Biradial Symmetry
• Swim with 8 rows of ciliary combs
• Have 2 long tentacles with sticky cells
• Eat large amounts of fish larva and plankton
• Diploblastic
• Mouth 2 anal pores