Supergroups Excavata and Amoebozoa – Lab Exercises

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Please choose one live specimen or prepared slide to image. Take a picture under the microscope and submit via Canvas. Make sure that your picture is appropriately centered, cropped, and focused. Add a scale bar.

Supergroup Excavata

Exercise 1: Examine prepared slides of Giardia

Examine prepared slides of Giardia cysts and trophozoites. Draw at least one of each. Using the 63x objective, measure the length and width.

Length____________ Width_____________                                                   Length____________ Width_____________

Exercise 2: Squeeze termites to isolate gut symbionts

Termites digest wood and other cellulose-containing plant material. To do so, they rely on endosymbionts that live in their hindguts. The termite microbiome includes bacteria, archaea, and unicellular eukaryotes. Many are parabasalids, including Trychonympha, or oxymonads, including Personympha.

  1. Make a hindgut symbiont preparation of one of your termites:
  1. Place a drop of water on a slide.
    • Grasp the front end of the termite with forceps.
    • Using a second pair of forceps, gently squeeze the hindgut, allowing the contents to drop onto the slide.
    • Quickly coverslip the water/gut fluid.
  1. If you see endosymbionts, please alert your instructor before disposing of the slide. You may want to use one of the microscopes with phase contrast/darkfield for a better view.

Exercise 3: Examine prepared slides of kinetoplastids

Examine prepared slides of trypanosomes. The majority of cells you will see are blood cells, with the trypanosomes among them. Draw a trypanosome among blood cells and measure its length and width. 

Exercise 4: Examine live culture of Euglena

  1. Make a wet mount of Euglena by adding a drop of culture to a slide and covering it with a coverslip.
  2. Observe the Euglena. 
    1. How quickly are they moving?
  3. Make a second wet mount, this time using a drop of Protoslo (methyl cellulose) to slow their movement.
  4. Try to identify the nucleus, flagellum, eyespot (small red dot near flagellar attachment), and chloroplasts.

Draw a Euglena cell, labeling the parts you are able to identify.

Supergroup Amoebozoa

Exercise 5.1: Examine and feed naked amoeba Amoeba proteus

Carefully pipet an amoeba into a concave slide. If there is not already food in the culture, add a drop of Chilomonas and observe the amoeba. Draw the amoeba and label any structures that you can identify. Is the amoeba feeding?

Exercise 5.2: Examine and feed naked amoeba Chaos carolinensis

Carefully pipet a live Chaos into a concave slide. You may wish to use the stereo microscope to locate a Chaos. Add Paramecium and observe the amoeba. Draw the amoeba and label any structures that you can identify. Is the amoeba feeding?

Exercise 6.1: Examine testate amoeba Arcella vulgaris

Make a wet mount to observe Arcella. Can you see pseudopodia extending from the test? Draw a cell.

Exercise 6.2: Examine testate amoeba Difflugia lobostoma

Make a wet mount of Difflugia. Can you see pseudopodia extending from the test? Draw a cell. What differences do you observe between the test of Arcella and Difflugia?

Do you observe Difflugia feeding on the charophyte?

Exercise 7.1: Examine plasmodial slime mold Physarum polycephalum. 

Observe under the stereo microscope. Do you see cytoplasmic streaming?

Exercise 7.2: Build a maze for Physarum polycephalum

Physarum polycephalum is noted in the scientific literature for solving mazes, by connecting food sources with the shortest path. You will build a maze for the slime mold and allow it grow throughout the dish. 

  1. In groups of 4-5, build a small maze with Lego that will fit in a 100x20mm Petri plate. 
  1. Fill the maze with agar to cover the bottom of the dish. Do not overfill the dish.
  2. Allow agar to cool and solidify.
  4. Use sterile forceps to place an oat or filter paper colonized with P. polycephalum (culture side down) in the maze. (you can flame the forceps to sterilize them). 
  5. Add 2-5 oats to the maze.
  6. Seal the sides of the plate with Parafilm®.
  7. One group member can take the culture home and take pictures of slime mold growth to assess whether the slime mold finds the shortest path between food sources.
Physarum after three days of growth through a student-built maze
Melissa Hardy, CC BY-SA 4.0

Exercise 8: Examine cellular slime mold Dictyostelium discoideum

Observe the culture of Dictyolstelium under the stereo microscope. Can you see fruiting bodies?