Protozoan Taxonomy
2 likes1,176 views
The document provides a comprehensive overview of protozoan taxonomy, detailing the classification and characteristics of various groups including flagellates, ciliates, and amoebae. It discusses the historical context of protozoa discovery, their ecological roles, and the significance of certain species as pathogens. The document includes information on the life cycles of parasites like Plasmodium and Toxoplasma, highlighting their impact on humans and other animals.
Protozoan Taxonomy
- 2. Outlines: Introduction Animal-like protists Classification of Phylum Protozoa Subphylum Super classes Classes References
- 3. Introduction: • In 1674, Antony van Leewenhoek described the first protozoan “animalcule”. • The protozoa were classified into four major groups based on their means of locomotion. Flagellates (Mastigophora) Cilia (Ciliophora or Infusoria) Amoeba (Sarcodina) Sporozoa
- 4. Cont... • Recent morphological, biochemical, and phylogenetic analysis have resulted in the development of a higher-level classification for the protists, including the protozoa. • In 2005, this scheme as a proposed by the International Society of Protistologists.
- 5. Animal-like Protists: • Animal-like protists are called protozoa. • Protozoa are single-celled eukaryotes that share some traits with animals. • Protozoa defined as “microscopic acellular animals existing singly or in colonies, without tissue and organs, having one or more nuclei”. • They are heterotrophs. • Animal- like protists include the flagellates, ciliates, and the sporozoans.
- 6. Classification of Phylum Protozoa
- 7. Phylum Sacromastigophora: • With over 18,000 described species, Sarcomastigophora is the largest protozoan phylum and has the following characteristics: • Unicellular or colonial • Locomotion by flagella, pseudopodia, or both • Autotrophic , saprozoic (living in decaying organic matter), or heterotrophic. • Single type of nucleus • Sexual reproduction (usually)
- 8. Subphylum Mastigophora: (Flagellum Locomotion) • Members of the subphylum Mastigophora (masti- gofo-rah) use flagella in locomotion. • Flagella may produce two-dimensional i. whiplike movements or ii. helical movements. • These movements that push or pull the protozoan through its aquatic medium.
- 9. Class Phytomastigophorea: (Phytoflagellated protozoa) • The subphylum Mastigophora has two classes. • It possess chlorophyll and one or two flagella. • Phytomastigophoreans produce a large portion of the food in marine food webs. • Much of the oxygen used in aquatic habitats comes from photosynthesis by these marine organisms.
- 10. Cont… • Marine phytomastigophorean include the dinoflagellates , have one flagellum that wraps around the organism in a transverse groove. • The primary action of this flagellum causes the organism to spin on its axis. • A second flagellum is a trailing flagellum that pushes the organism forward. • In addition to chlorophyll, many dinoflagellates contain xanthophyll pigments, which give them a golden brown color.
- 11. Cont… • At times, dinoflagellates become so numerous that they color the water. • Several genera, such as Gymnodinium, have representatives that produce toxins. • Periodic “blooms” of these organisms are called “red tides” and result in fish kills along the continental shelves.
- 12. Cont… • Humans who consume tainted molluscs or fish may die. • The Bible reports that the first plague Moses visited upon the Egyptians was a blood-red tide that killed fish and fouled water. • Indeed, the Red Sea is probably named after these toxic dinoflagellate blooms. • Phyloflagellated protozoa possess one or two flagella and produce a large portion of the food in marine food webs.
- 13. Cont... Oxygen used in aquatic habitats comes from photosynthesis by these marine protozoa. Euglena is a fresh water . Each chloroplast has a pyrenoid, which synthesis and stores polysaccharides. In the dark, euglenoids lack chloroplasts and are always heterotrophic
- 14. Euglenozoa: • Members of the Euglenozoa are either; • Phytoflagellated (photosynthesizing) protozoa that possess chlorophyll and acquired their chloroplasts through endosymbiosis • Zooflagellated (particle-feeding and parasitic) protozoa. • They have one or two flagella inserted into an apical pocket, possess two kinetosomes and the mitochondria have discoid cristae.
- 15. Cont.. • Euglena orients toward light of certain intestities. • Pigment shield (stigma) covers a photoreceptor at the base of the flagellum. • The stigma permits light to strike the photoreceptor from only one direction and move in relation to a light source. • Euglenoid flagellates are haploid and reproduce by longitudinal binary fission. • Sexual reproduction in these species is unknown.
- 17. Class Zoomastigophorea (Zooflagellated protozoa) • Members of the class Zoomastigophorea lack chloroplasts and are heterotrophic. • Protists also have a single, large mitochondrion that that contains an organized mass of DNA called a kinetoplast. • Most important species is Trypanosoma brucei. • Species are divided into three subspecies T. b. brucei, T. b. gambiense often reffered as the Trypanosoma brucei complex.
- 18. Cont… • Three subspecies is a parasite of non-human mammals: • Two cause Africa sleeping sickness in humans and Tsetse flies are intermediate hosts and vectors of all three subspecies. • When a testse fly bites an infected human or mammal, it picks up parasites in addition to its meal of blood. • Trypanosomes asexually in the gut of the fly for about 10 days, then migrate to the salivary glands.
- 20. Cont... • When the infected testse fly bites another vertebrate host, the parasites travel with salivary secretions into the blood of a new definitive host. • Parasites multiply asexually in the new host and again transform through a number of body forms. • Parasites may live in the blood, lymph spleen, central nervous system and cerebrospinal fluid. • When trypanosomes enter the central nervous system, they cause general apathy, mental dullness and lack of coordination.
- 21. Cont… • “Sleepness” develops and the infected individual may fall asleep during normal daytime activities. • Death results from the pathology occuring in the nervous system, as well as from heart failure, • malnutrition, and • other weakened conditions. • If detected early, sleeping sickness is ciurable. • Infection has advanced to the central nervous system.
- 22. Subphylum Sarcodina: Pseudopodia and Amoeboid locomotion: • Members of the subphylum Sarcodina are the amoebae. • When feeding and moving, they form temporary cell extensions called pseudopodia. • Lobopodia are broad cell processes containing ectoplasm and endoplasm and are used for locomotion and engulfing food. • Filopodia contain ectoplasm only and provide a constant two-way streaming that delivers food in a conveyor-belt fashion.
- 23. Cont… • Reticulopodia are similar to filopodia, they branch and rejoin to form a netlike series of cell extensions. • Axpodia are thin, filamentous, and supported by a central axis of microtubules. • Food caught on axopodia can be delivered to the central cytoplasm of the amoeba. • This group lack a test, cell wall, or other supporting structures. • These amoebae are naked and normally found on shallow-water substrates of freshwater ponds, lakes, and slow-moving streams.
- 25. Superclass Rhizopoda: Class Lobosea: • The most familiar amoebae belong to the superclass Rhizopoda, Class Lobosea and the genus Amoeba. • These amoebae are naked (they have no test or shell) and are normally found on shallow-water substrates of freshwater ponds, lakes, and slow-moving streams. • Where they feed on other protists and bacteria.
- 26. Cont… • They engulf food by phagocytosis. • In the process, food is incorporate into food vacoules. • Binary fission occurs when an amoeba reaches a certain size limit. • Tests are protective structures that the cytoplasm secrets. • They may be calcareous, siliceous, and proteinaceous. • Tests may be composed of sand or other debris cemented into a secreted matrix.
- 27. Cont… • Arcella is a common freshwater, shelled amoeba. • It has a brown, proteinaceous test that is flattened on one side and domed on the other. • Pseudopodia project from an opening on the flattened side. • Difflugia is another common freshwater, shelled amoeba. • Its test is vase shaped and is composed of mineral particles embedded in a secreted matrix.
- 29. Entamoebida: • First rank have no flagella or centrioles. • Lack mitochondria. • All free-living amoebae are particle feeders, using their pseudopodia to capture food; few are pathogenetic. • Example: Entamoeba histolytica causes one form • of dysentery in humans. • Amoebic dysentry is a worldwide problem that plagues humans in crowded, unsanitary conditions.
- 30. Cont… • Amoeba live in the folds of the intestinal wall, feeding on starch and mucoid secretions. • They pass from one host to another in the form of cysts transmitted by fecal contamination of food or water. • After ingestion by a new host, amoeba leave their cysts and take up residence in the hosts intestinal wall. • It causing multiple of problems.
- 31. Subphylum Actinopoda: (Foraminifera, Heliozoans, Radialoria): • Foraminiferans are primarily a marine group of amoebae. • Foraminiferans possess reticulopodia and secrete a test that is primarily calcium carbonate. • As foraminiferans grow, they secrete new, larger chambers that remain attached to the older chambers. • Test enlargement follows a symmetrical pattern that may result in a straight chain of chambers or a spiral arrangement that resembles a snail shell.
- 32. Foraminifera: • Many of these tests become relatively large; For example: “Mermaid’s pennies,” found in Australia, may be several centimeters in diameter. • Foram tests are abundant in the fossil record since the Cambrian period. • They make up a large component of marine sediments, and their accumulation on the floor of primeval oceans resulted in limestone and chalk deposits. • The white cliffs of Dover in England are one example of a foraminiferan-chalk deposit.
- 33. Heliozoans: • Heliozoans are aquatic amoebae that are either planktonic or live attached by a stalk to some substrate. • (The plankton of a body of water consists of those organisms that float freely in the water.) • Heliozoans are either naked or enclosed within a test that contains openings for axopodia.
- 34. Radiolarians: • Radiolarians are planktonic marine and freshwater amoebae. • They are relatively large; some colonial forms may reach several centimeters in diameter. • They possess a test (usually siliceous)of long, movable spines and needles or of a highly sculptured and ornamented lattice. • When radiolarians die, their tests drift to the ocean floor.
- 36. Phylum Labyrinthomorpha: • The very small phylum Labyrinthomorpha consists of protozoa with spindle-shaped, nonamoeboid, vegetative cells. • In some genera, amoeboid cells use a typical gliding motion to move within a network of mucous tracks. • Most members are marine, and either saprozoic or parasitic on algae or seagrass. • Several years ago, Labyrinthula killed most of the “eel grass” (a grasslike marine flowering plant).
- 37. Phylum Apicomplexa: • Members of the phylum Apicomplexa are all parasites. Characteristics of the phylum include: • Apical complex for penetrating host cells • Single type of nucleus • No cilia and flagella, except in certain reproductive stages • Life cycles that typically include asexual (schizogony, sporogony) and sexual (gametogony) phases.
- 38. Class Sporozoea: • The most important species in the phylum Apicomplexa are members of the class Sporozoea. • The class name derives from most sporozoeans producing a resistant spore or oocyst following sexual reproduction. Some members of this class, including; • Plasmodium and coccidians, cause a variety of diseases in domestic animals and humans. • Many are intracellular parasites, and their life cycles have three phases.
- 39. Cont… • Schizogony is multiple fission of an asexual stage in host cells to form many more (usually asexual) individuals, called merozoites. • Some of the merozoites undergo gametogony, which begins the sexual phase of the life cycle. • The parasite forms either microgametocytes or macrogametocytes. • Microgametocytes undergo multiple fission to produce biflagellate microgametes that emerge from the infected host cell.
- 40. Cont… • The macrogametocyte develops directly into a single macrogamete. • A microgamete fertilizes a macrogamete to produce a zygote that becomes enclosed and is called an oocyst. • The zygote undergoes meiosis, and the resulting cells divide repeatedly by mitosis. • This process, called sporogony, produces many rodlike sporozoites in the oocyst.
- 41. Plasmodium Life Cycle: • One sporozoean genus, Plasmodium, causes malaria and has a long history. • Malaria contributed significantly to the failure of the Crusades during the medieval era, and along with typhus, has devastated more armies than has actual combat. • Recently (since the early1970s), malaria has resurged throughout the world. • Over 100 million humans are estimated to annually contract the disease.
- 42. l Life cycle of Plasmodium
- 43. Cont.. • The Plasmodium life cycle involves vertebrate and mosquito hosts. • A mosquito takes in gametocytes during a meal of blood, and the gametocytes subsequently fuse. • The zygote penetrates the gut of the mosquito and transforms into an oocyst. • Sporogony forms haploid sporozoites that may enter a new host when the mosquito bites the host. • The symptoms of malaria recur periodically and are called paroxysms.
- 44. Cont… • Chills and fever correlate with the maturation of parasites, the rupture of red blood cells, and the release of toxic metabolites. • Four species of Plasmodium are the most important human malarial species. • P. vivax causes malaria in which the paroxysms recur every 48 hours. • P. falciparum causes the most virulent form of malaria in humans.
- 45. Cont… • Other members of the class Sporozoea also cause important diseases. • Coccidiosis is primarily a disease of poultry, sheep, cattle, and rabbits. • Two genera, Isospora and Eimeria, are particularly important parasites of poultry. • Another coccidian, Cryptosporidium, has become more well known with the advent of AIDS since it causes chronic diarrhea in AIDS patients.
- 46. Cont… • Toxoplasmosis is a disease of mammals, including humans, and birds. • Sexual reproduction of Toxoplasma occurs primarily in cats. Infections occur when oocysts are ingested with food contaminated by cat feces. • Most infections in humans are asymptomatic, and once infection occurs, an effective immunity develops. • However, if a woman is infected near the time of pregnancy, or during pregnancy, congenital toxoplasmosis may develop in a fetus.
- 47. Cont… • Congenital toxoplasmosis is a major cause of stillbirths and spontaneous abortions. • Feruses that survive frequently show signs of mental retardation and epileptic seizures. • Congenital toxoplasmosis has no cure. • Toxoplasmosis also ranks high among the opportunistic diseases afflicting AIDS patients.
- 48. Steps to avoid infection: Steps to avoid infections by; • Toxoplasma include keeping stray and pet cats away from children’s • sandboxes; using sandbox covers; and awareness, on the • part of couples considering having children, of the potential dangers • of eating raw or very rare pork, lamb, and beef.
- 49. Phylum Microspora: • Members of the phylum Microspora commonly called microsporidia, are small, obligatory intracellular parasites. • Nosema bombicus parasitizes silkworms causing the disease pebrine, and N. apis causes serious dysentery (foul brood) in honeybees. • These parasites have a possible role as biological control agents for insect pests.
- 50. Cont… • For example, the U.S. Environmental Protection Agency. • It has approved and registered N. locustae for use in residual control of rangeland grasshoppers. • Recently, four microsporidian genera have been implicated in secondary infections of immunosuppressed and AIDS patients.
- 51. Phylum Acetophora: • Acetospora is a relatively small phylum that consists exclusively of obligatory extracellular parasites characterized by spores lacking polar caps or polar filaments. • The acetosporeans (e.g., Haplosporidium) primarily are parasitic in the cells, tissues, and body cavities of molluscs.
- 52. Phylum Ciliophora: • The phylum Ciliophora includes some of the most complex protozoa. • Characteristics of the phylum Ciliophora include: • Cilia for locomotion and for the generation of feeding currents in water. • Relatively rigid pellicle and more or less fixed shape. • Distinct cytostome (mouth) structure. • Dimorphic nuclei, typically a larger macronucleus and one more smaller micronuclei.
- 53. Cilia and other Pellicular Structures: • Cilia are generally similar to flagella, except that they are much shorter. • Many ciliates can reverse the direction of ciliary beating and the direction of cell movement. • Basal bodies (kinetosomes) of adjacent cilia are interconnected with an elaborate network of fibers that are believed to anchor the cilia and give shape to the organism.
- 55. Cont….. • Some ciliates have evolved specialized cilia. • Cilia may cover the outer surface of the protozoan. • Trichocysts: are pellicular structures primarily used for protection. They are rod like or oval organelles oriented perpendicular to the plasma membrane. • In Paramecium, they have a “golf tee” appearance. The pellicle can discharge trichocysts, which then remain connected to the body by a sticky thread.
- 56. Trichocysts :
- 57. Nutrition: • Some ciliates, such as Paramecium, have a ciliated oral groove along one side of the body. • Cilia of the oral groove sweep small food particles toward the cytopharynx, where a food vacuole forms. • When the food vacuole reaches an upper size limit, it breaks free and circulates through the endoplasm.
- 58. Cont… • Some free-living ciliates prey upon other protists or small animals. Prey capture is usually a case of fortuitous contact. • The ciliate Didinium feeds principally on Paramecium, a prey that is bigger than itself. • Didinium forms a temporary opening that can greatly enlarge to consume its prey
- 59. References: • Miller and Harley Book 5th and 10th Edition