Of the republic of kazakhstan state university

Phytoflagellates are primarily autotrophic and contain chlorophyll. When the chlorophyll is not masked by other pigments, a flagellate appears green in color, like the phytom onads and euglenids. If the xanthophylls dominate, the color is red,

orange, yellow, or brown.

Strict heterotrophic nutrition occurs in zooflagellates as well as some other groups, and there are many parasitic species. The mechanism s of food capture and ingestion vary greatly, and the methods employed by some of the better known groups will be described in the following sections Phytoflagellates store reserve foods, such as oils or fats, or they may store carbohydrates as typical plant starch or in other forms. In zooflagellates, glycogen is the usual reserve food product.

1 Flagellates are distinguished by the presence of one or more flagella.

3 The remaining heterotrophs (zooflagellates) are a small, heterogeneous assemblage. A few are free living, but most are parasitic, commensal, or

mutualistic in other animals.

4 Flagella (and cilia) are composed of microtubules surrounded by the plasma membrane. The arrangement of m icrotubules in which nine pairs (doublets) surround two central m icrotubules is with few exceptions characteristic of flagella and cilia in all eukaryote organism s. Movement of the organelle is thought to result from the sliding ofated with the microtubules relative to each other. Each flagellum (or cilium] arises from a basal body, or kinetosome.

attachment and the combined action, when there is more than one flagellum.

The subphylum Sarcodina contains those protozoa in which adults possess flowing extensions of the body called pseudopodia. Pseudopodia are used for capturing prey in all Sarcodina, and in benthic groups, pseudopodia are also used as locom otor organelles.

The subphylum includes the familiar amebas as well as many other marine, freshwater, and terrestrial forms. The slime molds are sometimes included in the Sarcodina, but in the following discussion, the slim e m olds will be considered

to be fungi and left to the mycologists.

The Sarcodina either are asymmetrical or have a spherical symmetry. They possess relatively few organelles and in this respect are perhaps the simplest

protozoa. However, skeletal structures, which are found in the majority of species, reach a complexity and beauty that is surpassed by few other organisms.

The presence of flagellated gametes among many Sarcodina and the tendency of many flagellates to lose their flagella during some phase of the life cycle, often becoming ameboid, are important reasons for uniting the mastigophorans and sarcodines within a single phylum. These facts would also seem to indicate that the Mastigophora are the ancestral group.

SUM M ARY

1. Members of the phylum Sarcodina are distinguished by the presence of flowing extensions of cytoplasm called pseudopodia, which are used in feeding and, in some, for locomotion. The pseupseudopodia are given different names, depending on their shape and structure.

by the nature of their skeletons and their pseudopodia.

permits the protrusion of cytoplasm , which may cover the exterior of the test. Long, delicate, and often anastomosing reticulopodia extend from the protruded cytoplasm and are used in food trapping and locomotion.

6 Heliozoans are spherical, radially arranged, floating, and benthic Sarcodina that are largely restricted to fresh water. Long, radiating, needle-like pseudopodia (axopods) are used in trapping food. The axopods arise from the interior (medulla) and extend through an outer ectoplasmic cortex, which is com m only vacuolated. The cortex often contains a siliceous skeleton of plates, tubes, and needles.

7 Radiolarians are marine planktonic Sarcodina with spherical bodies and radiating axopods. An organic capsule wall separates a central cortex from extracapsular cytoplasm . Radiolarians have complex skeletons of silicon dioxide or strontium

sulfate within the extracapsular cytoplasm , organized in the form of lattice spheres or radiating spines or both.

One to many flagella present. Asexual reproduction by binary, more or less symmetrogenic, fission. Autotrophic or heterotrophic or both.

Small flagellates with yellow or brown chromoplasts and two unequal flagella.

Siliceous scales commonly cover the body. M arine and freshwater. Chromulina,

Ochromonas, Synura.

Order Silicoflagellida [Chrysophyta).

Flagellum single or absent and chromoplasts brown. Internal siliceous skeleton.

Marine. Dictyocha. Known mostly from fossil forms.

Order Coccolithophorida (Haptophyta).

Tiny marine flagellates covered by calcareous platelets— coccoliths. Two flagella

and yellow to brown chromoplasts. No endogenous siliceous cysts. Coccolithus,

Rhabdosphaera.

Order Heterochlorida [Xanthophyta).

Two unequal flagella and yellow-green chromoplasts. Siliceous cysts. Heterochloris, Myxochloris.

Compressed, biflagcllate, with an anterior depression or reservoir. Two chromoplastids, usually yellow to brown or colorless. Marine and freshwater. Chilomonas is a com m on colorless genus in polluted water.

An equatorial and a posterior longitudinal flagellum located in grooves. Body either naked or covered by cellulose plates or valves or by a cellulose membrane.

Brown or yellow chromoplasts and stigma usually present, but there are many colorless species. Largely marine; some parasites. Includes the marine genera

Gonyaulax, N octiluca, Histiophysis, and Ornithocercus, and the marine and

freshwater genera Glenodinium , Gymnodinium,Ceratium , O odinium , and

Biflagellate, with no chromoplasts; internal siliceous skeleton. Mainly fossil. Ebria.

Elongated green or colorless flagellates with two flagella arising from an anterior recess. Stigma present in colored forms. Primarily freshwater. Euglena, Phacus,

‘ Order Chloromonadida (Chloromonadophyta or Rhaphidiophyta]

Small, dorsoventrally flattened flagellates with numerous green chromoplasts. Two flagella, one trailing. Gonyostom um .

Order Volvocida (Chlorophyta; order Volvocales).

Body with green, usually single, cup-shaped chromoplast, stigma, and often two to four apical flagella per cell. Some colorless forms. Many colonial species. Largely freshwater forms. Chlamydomonas,Polytomella,Haematococcus, Gonium, Pandorina, Platydorina, Eudorina, Pleodorina, Volvox.

Flagellates with neither chromoplasts nor leucoplasts. One to many flagella, in most cases with basal granule complex. Many commensals, symbionts, and

parasites.

Order Choanoflagellida.

Freshwater flagellates, with a single flagellum surrounded by a collar. Sessile, sometimes stalked, sometimes with lorica; solitary or colonial. Codosiga, Proterospongia, Salpingoeca.

Ameboid forms, with one to many flagella. Chiefly freshwater. M astigamoeba, Dimorpha.

One or two flagella emerging from a pit. Mostly parasitic. Bodo, Leishmania, Trypanosoma.

Gut parasites of insects or vertebrates, with two or four flagella. One flagellum associated ventrally located cytostome. Chilomastix.

Bilaterally symmetrical flagellates, with one or two nuclei,each nucleus associated with one to four flagella. Mostly parasites. Hexamita,Giardia.

Commensal or mutualistic flagellates in the guts of insects; a few in vertebrates. One to many nuclei, each nucleus associated with four flagella, some of which are turned posteriorly and adhere to body surface. Oxymonas, Pyrsonympha.

Parasitic flagellates. Four to six flagella, one of which is trailing. Trichomonas (Fig. 2 -9A).

Many flagella, with kinetosomes arranged in a circle, plate, or longitudinal or spiral rows. Symbionts in guts of termites, cockroaches, and wood roaches. Lophomonas, Trichonym pha, Barbulanympha.

Body covered by longitudinal, oblique rows of cilia rising from anterior subterminal rows. Two or many monomorphic nuclei. Binary fission generally symmetrogenic. Sexual reproduction involves syngamy with flagellated

gametes. Gut commensals of anurans; less commonly of fishes, salamanders, and reptiles. O palina, Zelleriella.
SYSTEM ATIC RESUME OF SUBPHYLUM SARCODINA

Protozoa with pseudopodia as feeding and locomotor organelles; flagella, when present, only in developmental stages. Little development of cortical organelles. Skeletons of various form s and composition characteristic of some groups.

Lobopodia, filopodia, or reticulopodia used for locomotion and feeding.

Pseudopodia, usually lobopods.

Amebas that lack shells.

Naked amebas that lack flagellated stages. Largely freshwater, some marine; many parasites. Chaos,Amoeba, Entameoba, Hydramoeba.

Naked amebas with flagellated stages. Marine, freshwater, and soil species. Naegleria, Acantham oeba.

Naked, multinucleated amebas with one pseudopod and no flagellated stages. Pelomyxa.

Amebas with shells.

Body enclosed in a shell or test with an aperture through which the pseudopodia protrude. Free living, largely in fresh water. A rcella, Difflugia, Centropyxis.

Amebas with filopods.

Naked amebas. Freshwater and parasites of algae. Vampyrella.

Shelled amebas. Mostly in fresh water and soil. Gromia,Euglypha.

Sarcodina with delicate granular reticulopodia.

Chiefly marine species with mostly multichambered shells. Shells may be organic, but most commonly are calcareous. Globigerina, Orbulina, D iscorbis, Spirillina, Nummulites.

Primarily floating or sessile Sarcodina with actinopodia radiating from a spherical body.

Radiolarians with a radiating skeleton of strontium sulfate; axopodia. Most without a central capsule separating endoplasm and ectoplasm . Marine. Acanthom etra.

Radiolarians with a siliceous skeleton and a perforated capsular membrane.

Radiolarians with a siliceous skeleton but a capsular membrane containing

only three pores. Aulacantha.

Class Heliozoa.

Without central capsule. Naked, or if skeleton present, of siliceous scales and

spines. Primarily in fresh water. Actinophrys, A ctinosphaerium , Camptonem a.

Lecture #2. Features of the life cycle and structure of Sporozoa.

1. 
   Features of the organization due to the parasitic way of life. Structure apical complex cells. Alternation of asexual and sexual reproduction.
   
2. 
   General characteristics Class spore.
   
3. 
   Sporozoa lifecycle.
   

Sporozoans are parasitic protozoa, living within or between cells of their invertebrate or vertebrate hosts. They belong to two phyla, the Apicomplexa and the Microspora, both form erly composing an old protozoan grouping, the Sporozoa. Sporozoan, which refers to the presence of sporelike stages, continues to be used as a com m on name.

Most known sporozoans and all those of known economic and medical importance belong to the phylum Apicomplexa, so named because of a complex

of ringlike, tubular, filamentous organelles at the apical end, visible only with the electron m icroscope (Fig. 2-21). The function of the apical complex is uncertain but may include entry into the host cell. One or more feeding pores are located on

the side of the body.

Figure 2-21 Lateral view of a generalized aptcomplexan sporozoan. (From Farmer, J. N., 1980: The Proto­zoa. С. V. Mosby Co., St. Louis, p. 360.)

PHYLUM APICOMPLEXA

With apical complex at some stage. Spores usually present but lacking polar filaments. All species parasitic.

Class Sporozoa.

Reproduction sexual and asexual.

Subclass Gregarinia.

Mature trophozoites large and occur in host's gut and body cavities. Par­asites of annelids and arthropods. Gregarina, Monocystis (common parasite of earthworm's seminal receptacles).

Subclass Coccidia. Mature trophozoites small and intracellular. Eimeria, Isospora, Aggregata, Plasmodium, Toxoplasma.

Class Piroplasmea.

Parasites of vertebrate red blood cells transmitted by ticks. No spores. Theileria, Babesia.

PHYLUM MICROSPORA

Spores with polar filament present. All species par­asitic. Nosema.

1 Sporozoans are parasitic protozoa belonging to two phyla, the Sporozoa and the Microspora. Some species possess sporelike infective stages, from which the name sporozoan is derived.

2 The phylum Apicomplexa contains the gregarines, which are parasites of insects and ane-lids, and the coccidians, which are intracellular parasites of gut and blood cells of vertebrates and invertebrates. Plasmodium, the causal agent of ma­laria, is the best known and most familiar coccidian.

3 The complex life cycles usually involve fis­sion (schizogony), sexual reproduction (gamogony), and spore formation (sporogony).

4 The phylum Microspora contains intracellu­lar parasites, especially of insects. The name mi­crospora is derived from the spore, which contains filaments that can be everted.
3. Sporozoa lifecycle.
The life cycle of apicomplcxans typically involves an asexual and a sexual phase (Fig. 2-22). An infective stage, called a sporozoite, invades the host and undergoes asexual m ultiplication by fission, producing individuals called merozoites. Merozoites can continue schizogamy but eventually form gametes (gamogony) that fuse to form a zygote. The zygote undergoes meiosis to form

sporozoites.

The nature and life cycle of apicomplexan sporozoans can be illustrated by the coccidians, which include the parasites that cause malaria in humans. Malaria continues to be one of the worst scourges of mankind. About 300 million people are believed to be infected each year. The untreated disease can be long lasting and terribly debilitating. Malaria has played a m ajor and often unrecognized role in

human history. The name means literally "bad air" because the disease was originally thought to be caused by the air of swamps and marshes. Although

malaria had been recognized since ancient times, the causative agent was not discovered until 1880, when a physician with the French army in North Africa identified the coccidian parasite Plasmodium in the blood cells of a malarial patient. In 1887 the mosquito was recognized to be the vector.

The introduction of the parasite into a human host is brought about by the bite of certain species of mosquitoes, which inject the sporozoites along with their salivary secretions into the capillaries of the skin (Fig. 2-23). The parasite is carried by the bloodstream to the liver, where it invades a liver cell. Here further development results in asexual reproduction through multiple fission. These

daughter cells invade other liver cells and continue to reproduce. After a week or so there is an invasion of red blood cells by parasites produced in the liver. Within the red cell the parasite increases in size and undergoes multiple fission. The individuals (merozoites) produced by fission within the red cells escape and invade other red cells. The liberation and reinvasion are not continuous but occur

simultaneously from all infected red blood cells. The timing of the event depends on the period of time required to complete the developmental cycle within the host's cells. The release causes chills and fever, the typical symptom s of malaria.

Eventually, some of the parasites invading red cells do not undergo fission but become transformed into gametocytes. The gametocyte remains within the red blood cell. If such a cell is ingested by a mosquito, the gametocyte is liberated within the new host's gut. After some further development, a male gametocyte (microgametocyte) fuses with a fem ale gametocyte (macrogametocyte) to

form a zygote. The zygote penetrates the stomach wall and gives rise to a large number of spore stages (sporozoites). It is these stages, which migrate to the salivary glands, that are introduced into the hum an host by the bite of the mosquito.

The asexual stage of other coccidians occurs in blood cells or in gut cells. A number of diseases of domesticated animals are caused by coccidians. The genus Eimeria, for example, affects chickens, turkeys, pigs, sheep, and cattle (Fig. 2-22).

Another common group of apicomplexans contains the gregarines, which attain the largest size among the sporozoans. They are parasites of invertebrates, especially annelids and insects, and therefore not of economic importance. Intracellular par­asitic species are only a few microns long, but those that inhabit the body or gut cavities of the host may reach 10 mm in length. The body of a gregarine trophozoite is elongate (Fig. 2-24), and the an­terior part sometimes possesses hooks, a sucker or suckers, or a simple filament or knob for anchoring the parasite into the host's cells. The host becomes infected through ingesting spores containing sporozoites of the parasites (Fig. 2-25). Depending on the species, the liberated gregarine sporozoites either remain in the gut of the host or penetrate the gut wall to reach other areas of the body. The life cycle commonly lacks schizogony.

Members of the class Piroplasmea are another small group of sporozoans that also attack the red blood cells of vertebrates. Spores and gametes are not produced, and the parasites are transmitted by ticks. Pathogenic infections in cattle and other do­mesticated animals are of considerable economic importance.

The phylum Microspora contains a smaller number of intracellular parasites, but they are found in most animal groups, especially arthro­pods. They lack the apical complex of other spo­rozoans, and the sporelike stage is characterized by a polar filament that is extruded when this stage is taken into the host. The filament appears to be in­volved in some way with the invasion of the host's cell. As parasites of the honeybee and silkworm, the microsporidians are of economic importance. One of the early studies of sporozoans was that of Pasteur in 1870, on Nosema bombycis in silk­worms.

Figure 2-22 Life cycle of an eimcriid coccidian, a destruc­tive intracellular parasite of the gut epithelium of many verte­brates, including domesticated buds and mammals.

IN RED BLOOD CELL IN RED BLOOD CELL IN LIVER CELL

(gametocytes) (merozoites) (cryptozoites)
Figure 2-23 The life cycles of Plasmodium in a mosquito and in man. Reinvasion of liver cells in the tissue cycle does not occur in Plasmodium falciparum.

Figure 2-24 Trophozoites of the gregarinc Gregarina gamhami attacking the midgut epithelium of a locust.

Figure 2-25 Life cycle of a gregarine, Stylocephalus longicollis, an intestinal parasite of a beetle. There is no schizogony in this species.

1. 
   General characteristics of ciliates as the most highly differentiated and protozoa.
   
2. 
   Reproduction of ciliates (conjugation).
   
3. 
   The main classes of ciliates.
   

The phylum Ciliophora is the largest and the most homogeneous of the principal protozoan groups, and all evidence indicates that they share a com­mon evolutionary ancestry (Fig. 2-43). Some 7200 species have been described, and many groups are still not well known.

All possess cilia or compound ciliary structures as locomotor or food-acquiring organelles at some time in the life cycle. Also present is an infraciliary system, composed of ciliary basal bodies, or kinetosomes, below the level of the cell surface and associated with fibrils that run in various direc­tions. Such an infraciliary system may be present at all stages in the life cycle even with marked reduc­tion in surface ciliation. Most ciliates possess a cell mouth, or cytostome. In contrast to the other pro­tozoan classes, ciliates are characterized by the presence of two types of nuclei: one vegetative (the macronuclcus, concerned with the synthesis of RNA as well as DNA) and the other reproductive (the micronucleus, concerned only with the synthe­sis of DNA). Fission is transverse, and sexual re­production never involves the formation of free gametes.

Ciliates are widely distributed in both fresh and marine waters and in the water films of soil. About one third of ciliate species are ecto- and endocom-mensals or parasites.