Lab: Study Notes on Protozoa and Fungus-like Protista

Introduction

  • Discussion focused on protozoa, the animal-like protista that do not photosynthesize and need to hunt for food.
  • Emphasis on the need to micro-pursue their food sources.

Phylum Amoebozoa

  • Definition: This phylum includes amoebas.

  • Cell Structure: Amoebas have a flexible cell membrane.

  • Movement: They can move their cell membrane around, extending parts of their body as extensions by extruding the cytoplasm.

  • Pseudopodia Formation:

    • Definition: Pseudopodia are extensions of the amoebas used for both movement and feeding.
    • Process of Feeding: When two sides of the pseudopodia connect, they close the membrane, enclosing their prey. This process is called phagocytosis.

  • Genus:

    • Amoeba: A key genus within the phylum.
    • Pelomyxa: Initially mentioned but later crossed out due to similarity to amoeba.

  • Coloration: Amoebas naturally lack color but can appear stained in different colors (e.g., pink, blue).

Phylum Foraminifera

  • Name Meaning: The suffix 'fera' means 'to have'; 'foramen' means 'hole'.
  • Description: Includes organisms that have shells with holes, resembling amoebas inside these shells.
  • Shell Characteristics: When they die, their shells accumulate on the sea floor, contributing to the formation of sand.
  • Genus: No specific genus mentioned as there are multiple species.

Phylum Actinopoda

  • Similarity to Foraminifera: Actinopoda features amoeba-like organisms with an internal skeleton.
  • Movement: These organisms also extend pseudopodia to capture prey.
  • Shell Formation: When they die, their internal skeletons remain on the sea floor, contributing to the sand.
  • Common Name: Radilaria.

Phylum Zoomastigophora

  • Meaning of Suffixes: 'Zoo' refers to animals, while 'mastigo' means whip, indicating whip-like flagella.
  • Key Genera:
    • Giardia: Causes ‘beaver fever’; arises from consuming unfiltered water, resulting in intestinal parasitism and diarrhea.
    • Notable Facts: Giardia is small, often camouflaged in pond scum, and reproduces via cell division, where the two nuclei remain adjacent.
    • Trypanosoma:
    • Species: Includes Trypanosoma brucei gambiense and Trypanosoma cruzi.
    • Health Impact: Both are blood parasites that infect red blood cells.
    • Physical Characteristics: Undulating membrane for movement, slightly larger than red blood cells, requiring oil for microscopy.

Phylum Ciliophora

  • Meaning of Suffix: 'Cilio' refers to cilia, tiny hair-like structures used for movement.
  • Key Genera:
    • Paramecium: Relying significantly on cilia for swimming.
    • Stentor: Uses cilia to create a vortex for feeding, capturing water to trap prey.
    • Notably altered shape due to preservation, may appear as a round ball on slides.
    • Distinctive macronucleus visible under microscopy.

Phylum Apicomplexa

  • Key Genus: Plasmodium, known to cause malaria.

  • Characteristics:

    • An intracellular blood parasite, infects red blood cells, with merozoites bursting from infected cells to propagate.
    • Requires oil for visualization due to small size.

  • Other Genera:

    • Gregorina: Noteworthy for its structure resembling two connected soda bottles.
    • Some specimens are stained purple, while others remain unstained.

Fungus-Like Protista

Phylum Oomycota

  • Definition: Typically referred to as water molds; they exhibit fungus-like properties.
  • Genus: Saprolegnia, commonly found in fish tanks.
  • Reproductive Structures: Characterized by bulbs containing spores resembling a cluster of eggs.

Phylum Myxomycota

  • Description: Known as slime molds, they are still classified under protista but exhibit unique behaviors.
  • Movement: Can crawl actively.
  • Learning Capacity: Notable experiments show these organisms can solve mazes, suggesting a primitive form of memory encoding.
  • Research Significance: Scientist explored slime molds' potential for understanding genetic memory by demonstrating learning through maze pathways.

Practical Considerations for Lab Work

  • Students to utilize prepared slides with live observations of protozoa.
  • Specific organisms require oil immersion for clarity, particularly Giardia, Trypanosoma, and Plasmodium.
  • Virtual considerations for usage and cleaning of slides with alcohol and paper towels.

Conclusion

  • Review of protozoan diversity and their ecological significance is emphasized.
  • Important to ensure proper slide handling and understand key praticial aspect of using the microscope effectively.