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Body Structure



Nervous System and Oxygen Transport

  • Length: approx. .5cm
  • Single Opening – mouth
  • Both sexual and asexual.
  • .

    • Lacks brain and spinal cord
  • Shape: cylindrical
  • Food enters the gastrovascular cavity.
  • Asexually by budding
  • Mesoglea contains nerve cells to distribute messages throughout the body.
  • Cell Layer: (2)
  • Endoderm- inner layer
  • Ectoderm: outer layer
  • Mesoglea: lies between the two layers.
  • Digestion begins with the release of specialized enzymes.
  • Phagocytosis: the process by which food particles are ingested by endoderm cells.
  • Sexually- Sexual organs are produced, Gonads: testes and ovaries.
  • Fertilization occurs when sperm swims to ovaries of another hydra.
  • Zygote develops attached to the wall of the parent and forms a gastrula that then drops from the parent .
  • Tentacles are another form of sensory organs.
  • Basal disk: Means for attaching to surfaces.
  • Food is distributed throughout the body.
  • Hydra emerges from its protective coat in the spring.
  • Lacks a special transport system.
  • Diffusion is the process by which oxygen moves in, and carbon dioxide moves out.
  • Tentacles : means for trapping food organisms.
  • Food is excreted through the mouth .
    • Diffusion is also the hydra’s means for intercellular circulation.




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    The hydra can be fed with brine shrimp larvae or Daphnia.



    brine shrimp

    Tentacles have a stinging device to immobilize large prey.


     Prepared Slides album

    Hydra (wet mount) 40x 100x 400x

    Hydra (longitudinal section) 100x 400x

    Hydra (cross sectional) 400x

    Hydra (nematocysts) 400x