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Cnidarians

  • Page ID
    2900
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    This laboratory exercise covers the following animals. You should learn this classification scheme and be able to classify the animals into these categories.

    Phylum: Cnidaria

    • Class: Hydrozoa (Hydra and relatives)
    • Class: Anthozoa (Sea Anemones and Corals)
    • Class: Scyphozoa (Jellyfishes)

    Read the Cnidarians section of the lecture notes.

    Hydrozoa

    Hydra

    1. Use a dropper to place a live Hydra on a slide. Examine the Hydra using a dissection microscope.

    Hydra (Live) X 40    
         
    Hydra (Live) tentacle
    X 100
       

     

    Click here: VIDEO - Hydra movement, X40, X100 (3.59 MB)

    2. Hydra reproduce both sexually and asexually by budding. Try to find a live Hydra with buds. If you cannot find a live Hydra budding, look for budding in a prepared slide of Hydra.

    Hydra budding
    This is a form of 
    asexual reproduction.
    Hydra budding

    3. Add a drop of vinegar to the slide containing Hydra. Describe what happened to the cnidocytes.

    Hydra (Live) Exposed to
    5% Vinegar Solution X 100
    Hydra (Live) Exposed to
    5% Vinegar Solution X 200

    3. Examine microscope slides of hydra l.s. and hydra c.s. Look for the presence of two tissue layers. Identify stinging cells (Cnidocytes) in a slide of the whole animal.

    Hydra l.s. X 100 Hydra c.s. X 100 Hydra c.s. X 200
     
    Portion of a Hydra tentacle showing cnidocytes 
    Hydra l.s. X 40 Hydra l.s. with ingested food X 40

    Obelia

    1. Examine a preserved specimen of Obelia in a jar.

    2. Examine a microscope slide of Obelia. Find feeding polyps and reproductive polyps.

    3. Examine a microscope slide of an Obelia medusa. What reproductive cells are produced by Obelia medusae?

    Obelia, preserved specimen Obelia Colony X 40 Obelia medusa X 100
         
       
    Obelia medusa in feeding
    position X 100
       

    Other Hydrozoans

    1. Examine preserved specimens of Gonionemius, Polyorchis, and Physalia.

    Gonionemus, preserved Polyorchis, preserved Portuguese Man-Of-War

    Sea Anemones and Coral (Class Anthozoa)

    1. Examine a sea anemone and coral.

       
    Sea anemone, preserved    
         
    Astrangia (Northern Coral)
    Skeleton
    Coral Skeleton Coral Skeleton

    Jellyfish (Class Schyphozoa)

    Examine preserved jellyfish on display.

    Aurelia