Faunal Diversity

General Characteristics of Phylum Protozoa

  • Definition: Protozoa are unicellular organisms, mostly microscopic in size.

  • Habitat: They can be free-living or parasitic. Found in:

    • Marine environments

    • Freshwater

    • Damp soils

    • Some are saprophytes and commensals.

  • Body Structure:

    • The body can be naked or covered with a definite pellicle.

    • Protoplasm is divided into two layers:

    • Ectoplasm: Outer layer

    • Endoplasm: Inner layer

  • Respiration: Takes place through the general body surface via the process of diffusion.

  • Nutrition Types:

    • Holozoic: Animal-like nutrition

    • Holophytic: Plant-like nutrition

    • Saprophytic or parasitic: Decomposing or living off other organisms

Classification of Protozoa by Locomotory Organs

  1. Rhizopoda / Sarcodina

    • Locomotion: Pseudopodia

    • Body Structure: Lacks a definite pellicle

    • Nutrition: Holozoic or saprozoic

    • Examples: Amoeba, Entamoeba

  2. Ciliata

    • Locomotion: Cilia

    • Body Structure: Has a definite pellicle

    • Nutrition: Holozoic

    • Examples: Paramecium, Vorticella

  3. Flagellata

    • Locomotion: Flagella

    • Body Structure: Thin pellicle

    • Nutrition: Autotrophic or heterotrophic

    • Examples: Euglena, Trypanosoma

  4. Sporozoa

    • Locomotion: Absent locomotory organelle

    • Body Structure: Exclusively endoparasitic, no definite contractile vacuoles

    • Reproduction: Asexual reproduction via spores

    • Examples: Plasmodium, Monocystis

Detailed Study of Paramecium

Taxonomy

  • Kingdom: Protista

  • Phylum: Protozoa

  • Sub-phylum: Ciliophora

  • Class: Ciliate

  • Genus: Paramecium

  • Species: Caudatum

Habit and Habitat

  • Distribution: Freshwater organisms found in lakes, rivers, streams, and ponds, particularly in stagnant water with abundant organic matter.

  • Feeding: Paramecium feeds on bacteria, small protozoa, and decomposing organic matter using oral cilia.

Structure

  • Shape: Slipper-like due to cell structure resembling the sole of a shoe.

  • Cytoplasm Divisions:

    • Ectoplasm: The outer distinct part

    • Endoplasm: Inner granular part

  • Components:

    1. Cilia:

    • Hair-like structures distributed uniformly (except at the posterior end)

    • Types:

      • Somatic Cilia: Aid in locomotion

      • Oral/Buccal Cilia: Assist in feeding by collecting food materials

    1. Pellicle:

    • Thin, elastic, layered membrane that covers the cytoplasm.

    1. Trichocyst:

    • Oval, elongated structures arranged perpendicularly in the pellicle’s inner wall.

    1. Oral Groove:

    • A large depression located on the ventrolateral side of the paramecium’s body.

    1. Cytopyge:

    • An opening on the ventrolateral side near the posterior end used for excretion.

    1. Nucleus:

    • Characterized by:

      • Micronucleus: Small, diploid, involved in reproduction.

      • Macronucleus: Larger, bean-shaped structure controlling metabolic activities.

Reproduction in Paramecium
Asexual Reproduction: Transverse Binary Fission

  • Condition: Occurs in favorable conditions (temperature and food availability).

  • Process:

    1. Formation of two contractile vacuoles on either side of a partition.

    2. Anterior part is called 'proter' and the posterior 'opisthe.'

    3. After division, both paramecia lead an independent life.

    4. Duration of binary fission: 30-120 minutes, varies with environmental factors.

    5. Typical success: 2-3 divisions per 24 hours, leading to 4-8 new individuals.

Sexual Reproduction: Conjugation

  • Process: Morphologically similar but physiologically dissimilar paramecia attach laterally to exchange nuclear material.

    1. Four haploid nuclei formed, three degenerate, remaining divides into two types:

    • Female Pronucleus: Large and stationary

    • Male Pronucleus: Smaller and migratory

    1. Pronuclei unite to form a diploid zygote nucleus.

    2. After zygote formation, ex-conjugants separate.

    3. Result: Formation of eight new paramecia from each conjugation event.

Significance of Conjugation

  • Resource Regeneration: Enhances part regeneration, improving efficiency for binary fission.

  • Two Macronuclei Formation: Enhances control over metabolic processes.

Modified Forms of Reproduction

  1. Autogamy:

    • A modified form of self-fertilization identified in species with bimicronucleus.

    • Occurs within a single individual.

  2. Cytogamy:

    • A sexual process similar to conjugation without nuclear exchange, where smaller paramecia temporarily unite.

Study of Plasmodium
Taxonomy

  • Kingdom: Protista

  • Phylum: Protozoa

  • Class: Sporozoa

  • Genus: Plasmodium

  • Species: Plasmodium vivax (Malarial Parasite)

Habit and Habitat

  • Distribution: Cosmopolitan, primarily found in tropical and subtropical regions.

  • Lifecycle: A digenetic intracellular parasite affecting humans and other vertebrates.

    • Malaria-Causative Species: Includes Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale.

Structure of Plasmodium
Trophozoite

  • Fully grown, amoeboid, and uninucleated form;

    • Surrounded by a plasma membrane;

    • Contains a nucleus with nucleolus and cytoplasm with dark granules.

    • Endoplasmic reticulum composed of vesicles.

    • Contains food vacuoles with hemosporin.

Sporozoite

  • Small (10-15 mm), sickle-shaped, motile, and uninucleated;

    • Composed of pellicle, cytoplasm, and nucleus;

    • Capable of wriggling movements.

Life Cycle of Plasmodium vivax

  • Hosts: Two-host lifecycle

    1. Asexual cycle in humans (intermediate host)

    2. Sexual cycle in female Anopheles mosquitoes (definitive host).

Asexual Cycle Phases in Humans

  1. Pre-erythrocytic Phase:

    • After a mosquito bite, sporozoites circulate and invade liver cells, forming schizonts.

  2. Exo-erythrocytic Phase:

    • Schizonts release crytomerzoites which invade fresh liver cells, forming new schizonts.

  3. Erythrocytic Phase:

    • Micro metacryptomerzoites enter RBCs, forming trophozoites that feed on hemoglobin and develop into signet ring structures. Resulting merozoites can continue the erythrocytic cycle or form gametocytes.

Sexual Cycle in Mosquitoes

  • Micro and macro gametocytes enter the mosquito; the nucleus of microgametes divides, leading to flagellated structures that fertilize macrogametes forming new sporozoites for transmission.

Symptoms of Malaria Fever

  • Stages of Symptoms:

    • Prodromal Stage: Mild symptoms such as headache, nausea, and loss of appetite.

    • Paroxysmal Stage: Severe symptoms including chills, shivering, high fever (up to 104°F), and excessive sweating after fever subsides from temperature peak. Anemia results from RBC destruction.

Treatment of Malaria Fever

  • Recommended Drugs:

    • Quinine, chloroquine, daraprin, atabrin, primaquine.

Control Measures for Malaria Parasite

  1. Destruction of Breeding Areas:

    • Drain swamps and stagnant water; consider kerosene oil for areas that cannot be drained.

  2. Larvae and Pupa Control:

    • Use kerosene, paris green powder, and DDT for effective larval and pupal destruction.

  3. Biological Control:

    • Introduce fish that feed on larvae; use ducks and floating plants for better management.

  4. Adult Mosquito Control:

    • Utilize burning sulfur, tar, and DDT for adult mosquito eradication.

Lifecycle Statistics

  • Incubation Times:

    • P. falciparum: Pre-erythrocytic: 12-11 days, Erythrocytic: 48 hours

    • P. vivax: Pre-erythrocytic: 14 days, Erythrocytic: 36-48 hours

    • Total merozoites after pre-erythrocytic cycle:

    • P. falciparum: 10,000

    • P. vivax: 24,000