Protozoa

presentation

1. Unicellular Eukaryotes Protozoan Groups 1

2. Unicellular Eukaryotes (protozoans) Origins of eukaryotes First evidence for life 3.5 bya These organisms were prokaryotes Eukaryotes arose by symbiogenesis (aka, endosymbiosis) whereby, one cell engulfed another Alpha-protobacterium derived energy from carbon compounds became mitochondria Cyanobacterium derived energy from sunlight became plastid, specifically chloroplast 2

3. Unicellular Eukaryotes (protozoans) Protozoan Literally “first animal-like organisms in time” Not animals, but with animal features Lack cell wall At least one motile stage during life 3

4. Unicellular Eukaryotes (protozoans) 4

5. Unicellular Eukaryotes (protozoa) Diversity 64,000 named species (Hickman et al. 2017) Possibly 250,000 species Difficulties from revisions and species concepts 5

6. Unicellular Eukaryotes (protozoa) General characteristics Many species are symbiotic (living with other species) Mutualistic, commensalistic, or parasitic Movement - once used for classification; no longer Flagella, cilia, and pseudopodia No germ layers, tissues, or organs present 6

7. Unicellular Eukaryotes (protozoa) Movement - once used for classification; no longer Flagella, cilia, and pseudopodia Flagella - generally few, long, and propel water parallel to the main axis of the flagella 7

8. Unicellular Eukaryotes (protozoa) Movement - once used for classification; no longer Flagella, cilia, and pseudopodia Cilia - many, short, and propel water parallel to surface on which its attached 8

9. Unicellular Eukaryotes (protozoa) Movement - once used for classification; no longer Flagella, cilia, and pseudopodia Pseudopodia - extensions of the cytoplasm 9

10. Unicellular Eukaryotes (protozoa) Microstructure of cilia and flagella 9+2 arrangement of microtubules (= axoneme) Where axoneme enters body, a plate of 9 microtubules triplets (= kinetosome) Identical to centrioles that organize the mitotic spindle 10

11. Unicellular Eukaryotes (protozoa) Functional components Nucleus Genetic material on chromosomes; communicates with cells via pores; nucleoli present, ciliates with two nuclei (macro and micro) Mitochondria Recovers energy from carbon bonds Golgi complex Participates in intracellular digestion Plastids Photosynthetic elements 11

12. Unicellular Eukaryotes (protozoa) Nutrition Phagocytosis - food particle enveloped by cell Creates a food vacuole; lysosomes will fuse with vacuole and excrete digestive enzymes Digested products are absorbed across vacuole membrane In some groups the cite of phagocytosis is fixed; not in others. Saprozoic feeding - absorb foods from the environment 12

13. Unicellular Eukaryotes (protozoas) Homeostatic functions and structures No circulatory, respiratory, or excretory system present Diffusion in all cases is sufficient No temperature regulation Osmoregulation by contractile vacuole 13

14. Unicellular Eukaryotes (protozoa) Reproduction Sexual reproduction in most; no embryological development Both syngamy and autogamy are known Asexual reproduction common Binary fission Schizogony Budding 14

15. Unicellular Eukaryotes (protozoa) Phylum Parabasala Approximately 400 species Presence of axostyle is diagnostic Have many flagella Some are of medical and veterinary importance E.g., Trichomonas , Tritrichomonas Trichomonas vaginalis STD - in humans Tritrichomonas foetus infertility and spontaneous abortion in cattle Trichomonas gallinae parasite of pigeons/doves and other birds 15

16. Unicellular Eukaryotes (protozoa) Phylum Parabasala 16

17. Unicellular Eukaryotes (protozoa) Phylum Euglenozoa Pellicle is present Divided into two subphyla - Euglenida and Kinetoplasta Euglenida are free-living; Kinetoplasta are parasitic 17

18. Unicellular Eukaryotes (protozoa) Phylum Euglenozoa Euglenida Chloroplasts with chlorophyll b Live in freshwater Single, long flagellum Often with red stigma (i.e., eyespot) Normally autotrophic, but can become saprozoic if held in darkness 18

19. Unicellular Eukaryotes (protozoa) Phylum Euglenozoa Kinetoplasta Some important parasites Flagella and undulating membrane for locomotion Trypanosoma brucei , transmitted by tsetse fly causes African sleeping sickness T. cruzi , transmitted by Triatoma, causes Chagas disease Leishmania spp., transmitted by sand flies, causes leishmaniasis 19

20. Unicellular Eukaryotes (protozoa) Phylum Ciliophora Many species have bodies entirely covered with cilia Others have cilia near oral region only Generally much larger than other protozoans Most are free-living, some commensals, some parasitic Great variation in body form Always multinucleate (macro and micronucleus) May possess trichocysts or toxocysts Defense and offense 20

21. Unicellular Eukaryotes (protozoa) Phylum Ciliophora 21

22. Unicellular Eukaryotes (protozoa) Phylum Dinoflagellata Important primary producers in marine ecosystems About half are autotrophic Typically with two flagella Found in grooves Body often covered in plates Important mutualism with corals as zooxanthellae Without zooxanthellae, corals don’t thrive 22

23. Unicellular Eukaryotes (protozoa) Phylum Dinoflagellata Some are bioluminescent Others produce toxins that can lead to fish kills (i.e., red tides) 23

24. Unicellular Eukaryotes (protozoa) Phylum Apicomplexa Almost all are endoparasitic Presence of unique organelles, the apical complex, is diagnostic Hypothesized to be useful for penetrating host’s cells and tissues Locomotor organelles are less known; pseudopodia is some reproductive stages. Plasmodium spp. responsible for causing malaria 24

25. Unicellular Eukaryotes (protozoa) Phylum Apicomplexa 25

26. Unicellular Eukaryotes (protozoa) Phylum Foraminifera Testate amoebas Pseupodia as reticulopodia Most are benthic Tests are chambered and made of calcium carbonate (most) Dead individuals make up ocean floor ooze Important for limestone and chalk 26

27. Unicellular Eukaryotes (protozoa) Phylum Foraminifera 27

28. Unicellular Eukaryotes (protozoa) Phylum Foraminifera 28

29. Unicellular Eukaryotes (protozoa) Phylum “Radiolaria” Testate amoebas Pseudopodia as axopodia Inhabit surface waters Tests may be silicate Form into chert 29

30. Unicellular Eukaryotes (protozoa) Phylum Viridiplantae Belongs in clade Plantae with familiar green plants and algaes Unicellular, colonial, and multicellualr Multicellular implies cellular division of labor Members are photosynthetic Use flagella to move Cells either zooids or daughter colonies 30

31. Unicellular Eukaryotes (protozoa) Phylum Amoebozoa Naked and testate forms Some notable disease causing species Acanthamoeba castellanii - kills cells of cornea, spread through improperly disinfected contact lenses. Entamoeba histolytica - amoebic dysentery Naegleria fowleri - brain-eating amoeba 31

32. Unicellular Eukaryotes (protozoa) Phylum Opisthokonta Also a clade which contains animals, fungi, and some unicellular eukaryotes Choanoflagellates are solitary or colonial Choanoflagellate morphology is similar to the collar cells of sponges Thus, they are hypothesized to represent a sister taxa to the animals. 32