Kingdom%20Animalia

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Kingdom Animalia

• Phylum Cnidaria

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Characteristics

• Radial or biradial symmetry
• Diploblastic organization
• Mesoglea between epidermis and gastrodermis
• Gastrovascular cavity
• Nerve net
• Cnidocytes used in defense and feeding

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Reproduction/Life Cycle

• Can be monoecious or dioecious
• Alternate generations between polyp and medusa
  form
• Polyp asexual and sessile
• Medusa dioecious and free swimming

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Reproduction Contd

• Planula Cnidaria larvae
• Polyps are produced by budding or planula
• Medusae formed by budding from a polyp body wall

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Feeding

• Use cnidocytes to stun or kill prey
• Tentacles contract to bring food to mouth
• Food is digested in gastrovascular cavity

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Support and Locomotion

• Hydrostatic Skeleton
• Some classes have longitudinal muscles that aid
  in movement
• Polyps somersault, inchworm, glide on base, and
  walk on their tentacles
• Medusae swim and float

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Classification

• Class Hydrozoa
• Class Scyphozoa
• Class Cubozoa
• Class Anthozoa

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Class Hydrozoa

• Mostly marine, but the only class with freshwater
  members!
• Alternate generations
• Mostly colonial polyps

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Obelia

• Gastrozooid feeding polyp formed from planula
  larvae
• Grows through budding into more gastrozooids
• Gonozooid reproductive polyp that forms medusa
  by budding
• Medusae then reproduce sexually

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Gastrozooid
Gonozooid
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Gonionemus

• Medusa predominant
• Has a velum (shelf-like lip that projects inward)
• Velum creates jet propulsion
• Mouth at end of a manubrium
• Nerve ring that coordinates swimming movements
• Statocyst responds to gravity

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Hydra

• Freshwater
• Polyps only, no medusae
• Testes form sperm by meiosis
• Ovaries form one egg each

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Physalia

• Portuguese man-of-war
• Colonial
• Cannot swim
• Cnidocytes in tentacles are lethal to small
  vertebrates and dangerous to humans

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Class Scyphozoa

• All marine
• True Jellyfish medusa dominant

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Stinging Nettle, Mastigias
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Aurelia

• Gastrodermal cells have cilia to circulate food
• Feeds on plankton
• Rhopalia chemoreceptors
• Lappets touch receptors
• Statocysts gravity sensors
• Ocelli - photoreceptors

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Class Cubozoa

• Medusae are cuboidal
• Polyps are reduced or absent
• Tentacles hang from corners

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Class Anthozoa

• Polyps only, no medusae
• Mouth has a pharynx
• Gastrovascular cavity is divided into sections
• Sexual and asexual reproduction

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Sea Anemones
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Corals