Cnidaria

• Cnidaria Classes:

  Hydrozoa, anthozoa, scyphozoa
• Cnidaria Body Forms:

  Polyp: sessile, asexual

  Mesua: pelagic, sexual
• Cnidaria Tissue Construction:

  • diploblastic (2 layers):
  • endoderm + ectoderm + mesoglea
  • gastrovascular cavity / ceolenteron
• Mesoglea:

  Non-living, gelatinous, in-between layer of the endoderm and ectoderm
• Cnidocyte [unique to cnidarians]:

  Cell containing nematocysts

  • singing apparatus + delivers toxins
  • captures prey + used as defense
• Planula:

  The larval stage.

  • contains endoderm, ectoderm, + blastophore / mouth
• Hydrozoa

  Alternates between polyp and medusa stages.

  Has Gastrozooids + Gonozooids
• Gastrozooids:

  Polyps specialized for feeding

  
• Gonozooids:

  Polyps specialized for reproduction

  • produces either sperm or eggs
• Scyphozoa: class comprising of jellyfish


  Defined by: medusa dominant, polyp reduced

  Contains:

  • medusa (oral side facing down + has oral arms that have nematocysts)
  • gastrovascular cavity (4-leaf clover)
  • gonads
  • rhopalia (small sensory structures) (have statocysts)
• Statocysts:

  Balance organs that are acted on by gravity.

  Helps organism remain upright + can tell which way its oriented.
• Anthozoa: flowering animals

  Defined by: loss of medusa, polyp only

  Subclass Hexacorallia

  • Actinaria
  • Scleractinia

  Subclass Octocorallia

  • Gorgonacea
  • Alcyonacea
  • Pennatulacea
• Actinaria: sea anemones

  In Subclass Hexacorallia

  Contains polyp, mouth, + ring of tentacles
• Scleractinia: true corals

  Colony of polyps that are connected by gastrovascular tissue

  • has external calcium carbonate skeleton
  • has tentacles + symbionts for feeding
• Gorgonacea: sea fans, sea whips


  • polyps surrounded by skeleton
• Alcyonacea: soft corals
• Pennatulacea: sea pens, sea pansies
• Sexual Reproduction In Corals: broadcast spawners + brooding (internal fertilization)