Invertebrata - Protozoa (PDF)

BIOLOGY II INVERTEBRATA UNICELLULAR EUKARYOTES PROTOZOAN GROUPS KINGDOM PROTISTA SUBKINGDOM PROTOZOA CHARACTERISTICS 1. Unicellular. 2. Microscopic. 3. Symmetry - none, bilateral, radial or spherical. 4. No germ layer. 5. Specialized organelles, no organs, no tissues; nucleus...

BIOLOGY II INVERTEBRATA UNICELLULAR EUKARYOTES PROTOZOAN GROUPS KINGDOM PROTISTA SUBKINGDOM PROTOZOA CHARACTERISTICS 1. Unicellular. 2. Microscopic. 3. Symmetry - none, bilateral, radial or spherical. 4. No germ layer. 5. Specialized organelles, no organs, no tissues; nucleus single or multiple. 6. Mostly free living: commencialistic, mutualistic or parasitic. 7. Locomotion - pseudopodia, flagella, cilia and direct cell movements. 8. Mostly naked, some with protective exoskeletons, ectoplasm, pellicle & test. 9. All types of nutrition: a) Autotrophic (manufacturing own nutrients by photosynthesis). b) Heterotrophic (depending on other plants or animals for food). c) Holozoïc (depending on other living organisms for food). d) Saprozoïc (depending on dead organic materials). 10. Asexual reproduction - binary fission, multiple fission or budding. Sexual reproduction - syngamy, conjugation & autogamy. FORM & FUNCTION BODY COVERINGS / EXOSKELETON 1. Mostly naked. 2. Ectoplasm. 3. Cell membrane or plasmalemma. 4. Pellicle. 5. Protective covering / exoskeletons of gelatinous, cellulose or chitin (test). ENDOSKELETON 1. Hydrostatic pressure. 2. Endoplasm. LOCOMOTION 1. pseudopodia, 2. cilia, 3. flagella, 4. direct cell movements. Pseudopodia a) Temporary extensions of cell-form & retract at different areas of surface. b) Plasmalemma covers ectoplasm which encloses endoplasm. c) Ectoplasm firm & gelatinous; endoplasm fluid (plasmasol). d) Movement of endoplasm - study (Hickman et al., 2017, p. 222-223). Thickening of ectoplasm to form hyaline cap. Endoplasm flows into hyaline cap. At tip: endoplasm is converted to ectoplasm, forming tube for forward flow. At posterior side: ectoplasm converts back to fluid endoplasm, replenishing flow. Types of pseudopodia:  lobopodia: Relative large, blunt extensions of the cell body containing both endoplasm and ectoplasm. Examples: Amoeba, Arcella, Difflugia.  filipodia: Are thin extensions, usually branching, containing only ectoplasm. Examples: Euglypha, Chlamydophrys. Euglypha  reticulopodia: Reticulopodia repeatedly rejoin to form a netlike mesh, containing only ectoplasm. Example: Globigerina.  axopodia: Long, thin pseudopodia supported by axial rods of microtubules, which are arranged in a definite spiral or geometrical array, and constitute the axoneme of the axopod. Examples: Actinophrys, Clathrulina. Cilia and Flagella Similarities:  Both protoplasmic extensions.  Nine pairs of longitudinal microtubules arranged in circle around central pair.  “9 + 2” configuration = axoneme.  Base: kinetosome = nine triplets of microtubules.  Axoneme covered with membrane continuous with cell membrane.  Functions: locomotion, create water current for feeding & handling food.  Base: kinetosome = nine triplets of microtubules. Differences: Cilia Flagella Short Long Numerous One to two Study: cilium / flagellum morphology, kinetosome / blepharoplast. EXCRETION & OSMOREGULATION 1. Contractile vacuoles pump to remove excess water from cytoplasm. 2. Also direct through body surface – diffusion. RESPIRATION Exchanges of O2 and CO2 occur by diffusion through cell membrane. NUTRITION & DIGESTION Autotrophic Heterotrophic 1. Euglena and Volvox -chlorophyll (autotrophic). 2. Some absorb nutrients from the water (saprozoïc / osmotrophs). 3. Ingest solid/liquid food - oral opening (cytostome) (holozoïc / phagotrophs). 4. Food digested within food vacuoles (phagositosis). 5. Lysosomes produced by Golgi bodies, contain digestive enzymes. Digested products are absorbed into surrounding cytoplasm and indigestible wastes are expelled to the outside.  Endocytosis – material brought into the cell. Exocytosis – material expelled from cell. Endocytosis includes two different processes: Phagocytosis – solid materials taken in. Pinocytosis – substances taken in are in solution. REPRODUCTION (i) Asexual reproduction a) Binary fission resulting in two daughter organisms similar to mother. Both nucleus and cytoplasm divide. Nucleus divides by mitosis. b) Budding involves unequal division; parent retains own identity, while forming internally and externally one or more small cells. c) Multiple fission (schizogony / sporogony). Nucleus divides a number of times, followed by division of organism into as many parts as there are nuclei. (ii) Sexual reproduction a) Formation and union of male and female gametes which unite to form a zygote. By division the zygote gives rise to new individuals. Isogametes – gametes of both sexes are alike in size and appearance. Anisogametes – gametes are different in form or size.  Syngamy: fertilization of one gamete with another individual gamete to form a zygote. Autogamy: condition in which the gametic nuclei produced by meiosis fuse within the same organism that produced them to restore the diploid number. b) Conjugation: temporary union of two individuals during which they exchange nuclear materials. CLASSIFICATION (Hickman et al., 2017, p. 227-243) Kingdom: Protista PHYLUM: VIRIDIPLANTAE Genus: Chlamydomonas Genus: Volvox PHYLUM: DIPLOMONDA Genus: Giardia PHYLUM: PARABASALA Order: Trichomonadida Genus: Trichomonas  Life cycle of Trichomonas vaginalis: PHYLUM: EUGLENOZOA SUBPHYLUM: Euglenida Class: Euglenoidea Genus: Euglena SUBPHYLUM: KINETOPLASTA Trypanosoma brucei gambiense cause African sleeping sickness. Trypanosoma cruzi causes Chagas disease. Genus: Leishmania (Leishmaniasis) Leishmania tropica (promastigote stage) Picture of a sand fly biting a human arm. PHYLUM STRAMENOPILES Genus: Actinophrium, Actinophrys PHYLUM: APICOMPLEXA Class: Gregarinea Genus: Gregarina Class: Coccidea Genus: Plasmodium PHYLUM: CILIOPHORA Genus: Paramecium Genus: Stentor Genus: Vorticella PHYLUM: DINOFLAGELLATA Genus: Ceratium Amebas PHYLUM: AMOEBOZOA (Rhizopodans) Genus: Amoeba Genus: Entamoeba PHYLUM: FORAMINIFERA (Granuloreticulosans) Genus: Globigerina PHYLUM: RADIOLARIA (Actinopodans) Genus: Tetrapyle Unicellular Eukaryotes PHYLUM: VIRIDIPLANTAE Contains autotrophic single-celled algae like: Chlamydomonas colonial forms like Volvox. Volvox globator Colonial flagellate. Freshwater, mostly green. Cellulose cell wall with 2 short flagella. Volvox = colony of thousands of zooids embedded in a gelatinous surface of a jelly ball. Each cell = nucleus, pair of flagella, large chloroplast & stigma. Division of labour – nutrition, locomotion, reproduction.  Asexual reproduction:  Mitotic division of 1 germ cell: form hollow sphere of cells.  Sphere turns inside out to form daughter cells/colony.  Many daughter colonies form inside parent.  Sexual reproduction:  Zooids differentiate into macrogametes or microgametes.  Microgametes form bundles of flagellated sperm.  Sperm surge for mature ovum.  Fertilization takes place.  Zygote develops and secretes hard, spiny protective shell.  Zygote undergoes repeated division; produces small colony. PHYLUM: EUGLENOZOA Longitudinal microtubules beneath cell membrane form a pellicle. Divided into two subphyla: EUGLENIDA and KINETOPLASTA.  Euglenida = free living  Kinetoplast = parasitic SUBPHYLUM: EUGLENIDA Chloroplasts contain chlorophyll b for photosynthesis. Characteristics: i. Protected by proteinaceous strips - pellicle. ii. Flagellum anterior extends from reservoir; second flagellum in reservoir. iii. Kinetosome at base of flagellum. iv. Body filled with chloroplasts, bearing chlorophyll. v. Paramylon bodies store food material. vi. Contractile vacuole empties into reservoir. vii. Eyespot or stigma for orientation to light. viii. Nutrition: autotrophic (holozoic) / saprozoic. ix. Reproduction: binary fission. Euglena viridis: SUBPHYLUM: KINETOPLASTA 1. Colorless, lack chromoplasts, are holozoïc or saprozoïc and symbiotic. 2. Many are parasitic. 3. Trypanosoma brucei gambiense cause African sleeping sickness in humans and T. brucei brucei in domestic animals. 4. Trypanosomes are transmitted by tsetse flies (Glossina spp.). 5. Trypanosoma cruzi causes Chagas disease in humans in Central America & South America. Self study: life cycles of: Trypanosoma brucei gambiense Trypanosoma brucei rhodesiense Diagnostic Stage trypanosomes multiply in peripheral blood early in the disease, later in lymph nodes and central nervous system Infective Stage and trypanosomes ingested TRYPOMASTIGOTE FORM: Method of Infection: by tsetse fly (Glossina spp) tsetse fly bites man, crithidial forms multiply trypanosomes from in fly gut, infective form salivary gland deposited moves to salivary gland PHYLUM: DIPLOMONADA Divided into: Retortamonads & Diplomonads. Diplomonads example: Giardia Trophozoites: Cysts:  Self study: Life cycle of Giardia lamblia PHYLUM: PARABASALA Order: Trichomonadida Genus: Trichomonas PHYLUM: STRAMENOPILES Genus: Actinophrium, Actinophrys ALVEOLATA Contains alveoli, membrane-bound sacs lying beneath cell membrane. 3 Groups: Ciliophora, Dinoflagellata & Apicomplexa. PHYLUM: CILIOPHORA (Ciliates) 1. Free living / commensal / parasitic. 2. Movement by cilia. 3. Multinucleated, large macronucleus and small micronucleus. 4. Pellicle (may consist only of cell membrane). 5. Cilia terminate in basal bodies (kinetosomes) beneath pellicle. 6. Kinety = cilia + kinetosomes + fibrils. 7. Holozoïc feeders (cilia to cytostome, to ciliated groove or cytopharynx, to food vacuole that receives enzymes (phagocytosis). 8. Undigested residues discharged through exocytosis, at cytopyge (excretory pore). 9. Trichocyst (defense = expel long thread-like structure) & Toxicyst = release poison to paralyze prey. Free-living ciliates: Paramecium caudatum: 1. Asymmetric with oral groove ventrally. 2. Pellicle clear, elastic membrane; covered by cilia. 3. Trichocysts embedded in ectoplasm. 4. Oral groove leads to cytostome, leads to cytopharynx, leads to food vacuole. 5. Cytoproct discharge faecal material out of body. 6. Water regulation: two contractile vacuoles present. 7. Macronucleus large (for metabolism and development). Micronucleus small (contains chromosomes). 8. Paramecia are holozoic, live on bacteria, algae. 9. Asexual reproduction: binary fission where micronucleus divides by mitosis and macronucleus divides amitotically. 10. Sexual reproduction is through conjugation and autogamy. Vorticella: Vorticella: Stentor: Binary fission (p. 233): Conjugation (p. 234): Sexual Reproduction: Individuals come into contact on oral surface; Micronuclei prepare to divide; Micronuclei divide twice via meiosis; Forming 4 haploid nuclei; 3 nuclei degenerate; Remaining nuclei divides to form “male” & “female” pronuclei; Male pronuclei are exchanged between conjugants; “male” & “female” pronuclei fuse to form synkaryon (diploid); Conjugants separate; Synkaryon divides 3 times forming 8 micronuclei; Old macronucleus gradually resorbed; 4 micronuclei become macronuclei; 3 micronuclei are resorbed; 1 micronuclei divide twice; End in daughter cells: 4 macronuclei with 4 micronuclei. Autogamy: Autogamy is the process of self-fertilization, similar to conjugation, except that there is no exchange of nuclei. After disintegration of the macronucleus and meiotic divisions of the micronucleus, the two haploid pronuclei fuse to form a synkaryon that is homozygous. PHYLUM: DINOFLAGELLATA Members are autotrophic and heterotrophic. Bear two flagella, one equatorial and one longitudinal. Examples: Ceratium, Noctiluca & Gymnodinium. Noctiluca can produce light (bioluminescence). Red tides are population explosions (or blooms) of dinoflagellates. Self-study: “Why do they produce a “red tide”? Alexandrium sp., a red tide organism.  Dinoflagellates are the organisms responsible for red tide events, or "harmful algal blooms". Blooms (population explosions) of dinoflagellates are sometimes called "red tides" because dinoflagellates can reach such high densities that they actually change the color of the water in which they reside. Depending on the pigments present in these dinoflagellates, these tides actually appear brown, red, orange, or yellow. A number of dinoflagellate species release toxins into the water, killing many aquatic animals and poisoning others with sub-lethal doses of toxins. The primary function of these compounds is probably defensive, warding off or poisoning grazers, and perhaps preventing competing algal species from gaining a foothold in non-specific mats of plankton.  Filter feeders (e.g., shellfish) are particularly vulnerable to these compounds because they actively ingest plankton. Heterotrophs (e.g., humans) that eat poisoned animals are often themselves unintended victims of dinoflagellate's defensive chemicals, contracting such conditions as paralytic shellfish poisoning. The compounds involved are neurotoxins, poisons that attack the central nervous system, producing symptoms such as delirium and respiratory paralysis. One red tide organism, Pfiesteria, is unusual in that it uses toxins specifically to kill fish, stunning them and then feeding on their tissues. Pfiesteria also produce some of the most ecologically severe red tides, sometimes killing enormous numbers of fish. It is not clear how Pfiesteria affect humans, but there does seem to be considerable evidence that people exposed to its toxin by physical contact with affected fish or water containing Pfiesteria suffer various symptoms (e.g., skin lesions and loss of cognitive functions). PHYLUM: APICOMPLEXA (Sporozoans) 1. Unique apical complex. 2. Endoparasitic. 3. Develop spores (oocysts). CLASS: COCCIDEA Self study: Life cycle of Plasmodium. Trophozoites of Plasmodium falciparum, which is responsible for cerebral malaria. Trophozoite of Plasmodium ovale. The presence in a thin blood film of a number of irregularly-shaped host red blood cells such as the one depicted here is a feature of P. ovale infection that is important diagnostically. The characteristic crescentic gametocyte of Plasmodium falciparum. Gametocytes initiate infection in the mosquito vector. Dormant stages of malaria parasites are obstacles to the eradication of malaria (since 2007, the new ultimate goal of malarial research) because their activation leads to production of gametocytes which, in turn, results in renewed trans-mission of malaria in human populations. Research Notes Prof. Miles Markus University of the Witwatersrand In the 1970s, Professor Miles Markus (University of the Witwatersrand) correctly predicted that a “hypnozoite” stage (he coined the term) would be found to be part of the malarial parasite’s life cycle. Hypnozoites are thought to give rise to relapse in particular types of malaria. He has now raised the question of whether there could be a second source of recurring Plasmodium vivax malaria, a clinical phenomenon that has intrigued and puzzled humans for millennia. Recent research results suggest that latent merozoites might be a cause.  Plasmodium vivax, the cause of relapsing benign tertian malaria. Infected erythrocytes become enlarged and stippling is evident in the host cells. Reference: Markus, M.B. 2011. Origin of recurrent Plasmodium vivax malaria – a new theory. South African Medical Journal 101: 682–4; Markus, M.B. 2012. Dormancy in mammalian malaria. Trends in Parasitology 28: 39–45. Toxoplasma gondii  Definitive host: cats (Felidae) 3 – 10 days bradyzoites ≥ 13 days tachyzoites sporogony in faeces ≥ 18 days oocysts oocysts  PARABASALIDS PHYLUM: AMOEBOZOA AMEBAS 1. Movement -pseudopodia (lobopodia). 2. Pellicle consists of cell membrane. 3. Prominent ectoplasm and endoplasm. 4. Nutrition: holozoïc by phagocytosis. 5. Reproduction: binary fission. Amoeba proteus Many amebae are endoparasitic, mostly in the intestine of man or other animals. Entamoeba histolytica infects cell-linings in the human colon, causing amebic dysentery. ENTAMOEBIDAE Life inside humans or other animals. Have branched pseudopodia – rhizopod amebas. Self study: Life cycle of Entamoeba histolytica. PHYLUM: FORAMINIFERA CLASS: GRANULORETICULOSEA Pseudopodia extend through openings in test, branch and run together to form a protoplasmic net (reticulopodia). Mostly foraminiferans. Skeletons of calcium carbonate. Example: Globigerina ACTINOPOD AMEBAS PHYLUM: RADIOLARIA CLASS: ACTINOPODA Known as radiolarians. All with axopodia. Have a protective test; skeletons made of silica or strontium sulfate. Example: Tetrapyle PHYLOGENY 1. Ancestral eukaryote diversified into many distinct clades. 2. Most characteristics for phylogenetic analyses come from structural features of protozoan organelles. 3. Ancient organelles formed through symbioses among prokaryotes should be distinguished from more recently acquired organelles formed through secondary symbioses among eukaryotes. 4. As mitochondria were added to eukaryote cells, developmental lines leading to Fungi and Metazoa split from those leading to other phyla. 5. Some protozoans like choanoflagellates are phylogenetically related to fungi and animals, and may share a recent common ancestor with sponges. 6. The common ancestor of green plants and green algae acquired their chlorophyll- bearing plastids by symbiogenesis with a cyanobacterium, having two membranes. 7. In Euglenozoa acquisition of their plastids apparently occurred after divergence from ancestors of Kinetoplasta. 8. Among alveolates, many dinoflagellates are photo-autotrophs with their chloroplasts, but some lost them. 9. Apicomplexans have a small circular, plastid-like DNA that was possibly inherited from their common ancestor with dinoflagellates. 10. Ancestors of ciliophorans either lost their plastid symbionts or diverged from their common ancestor with dinoflagellates before secondary symbiogenesis occurred.  POSSIBLE PHYLOGENETIC DEVELOPMENT OF PROTOZOA Bacteria Flagellates Euglenoidea Kinetoplastida Plants Animals colonial (chloroplasts) (no chloroplasts) multi-cellular (autotrophic) (holozoic / saprozoic / parasitic cell aggregation differentiation Amebas Ciliates (free-living) movement ciliary coordination cell-cell communication Parasitic Apicomplexa Metazoa SUMMARY & REVIEW QUESTIONS Study p. 244 and students should be able to answer Questions 1 - 18 (Hickman et al., 2017, p. 237). THE END