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ZOOLOGY-SEMESTER-I-Unit-I Unit I Phylum Protozoa General characters The Protozoa mark the beginning of animal life. Being the simplest in structure, protozoa are regarded most primitive or first animals (Gre. Protos-first, zoon- animal) of nature. Protozoa may be defined as microscopic & acellular animalcules, without tissues and organs, having one or more nuclei, but no nucleus ever in charge of a specialized part of cytoplasm. They exist either single or in colonies which differs from a metazoan in having all the individuals alike except when engaged in reproductive activities. They are usually microscopic animalcules, ordinarily not visible without a microscope, acellular found all over the world as they exhibit a great range of structural complexity and adaptations for all types of environmental conditions. Protozoans occur wherever moisture is present. Hence, they occur in seawater, in all types of fresh water & in the wet soil. Thus protozoans exhibit mainly two modes of life free living inhabiting fresh & salt water & damp places, parasitic living as ecto & endoparasites. There are many protozoa which are commensal & mutualistic. Majority of protozoa are solitary & some form colonies, the solitary forms are mostly free-living, whereas colonial ones are often attached. (Some colonial forms (Volvox) attain such degree of cellular interdependence that they approach a true multicellular level of structure. Body symmetry none, bilateral, radial. Or spherical, oval, bell shaped, spindle shaped, slipper like or irregular. Body naked or bounded by a pellicle, (theca, Lorica or silicious shell) often provided with simple to elaborate shells or exoskeletons. 1 Unit I Body form usually constant, varied in some. While changing with environment or age in many. Single cell body performs all essential & vital activities, which characterize the animal body, hence only sub-cellular physiological division of labour. Locomotor organelles are Finger-like Pseudopodia (Sarcodina) or Whip-like Flagella (Mastigophora) or Hair like Cilia (Ciliate) or Absent(Sporozoa) Nutrition Holozoic (animal-like), Holophytic (plant like), Saprozoic or Parasitic with or without definite oral & anal aperture. Digestion occurs intracellularly inside food vacuoles. Respiration and Excretion through general surface (diffusion) or through contractile vacuoles to remove soluble water matter through osmoregulation. In some forms excretion occurs through a temporary opening in ectoplasm or through permanent pore (cytopyge) Reproduction Asexual by binary or multiple fission and budding and Sexual by conjugation of adults (hologamy) or by fusion of gametes (syngamy) or (copulation, autogamy, paedogamy) Life history often complicated with alternation of asexual and sexual phases. Encystment commonly occurs to help in dispersal as well as to resist unfavourable conditions of food, temp. and moisture. The single celled individual not differentiated into somatoplasm and germplasm, therefore exempted from natural death which is price paid for body. 2 Unit I About 50,000 known species. Nucleus is the seat of control of all vital activities of protozoan body. This is shown by the fact the denucleated organism soon dies. Nucleus is therefore most important organelle of every protozoan as indeed every metazoan cell. Classification of Protozoan Phylum protozoa is a large and varied group and poses a number of problems in its classification, 3 Unit I Classification of Protozoan Phylum Protozoa is a large and varied group and poses a number of problems in its classification. The following classification of Protozoa is based on the scheme given by the committee on taxonomy and taxonomic problems of the society of Protozoologists and mainly proposed by B.M. Honigberg and others (1964). It divides Protozoa first into 04- sub phyla:- I. Sarcomastigophora II. Sporozoa III. Cnidospora and IV. Ciliophora Brief outline of sub phylum Sarcomastigophora I. Sarcomastigophora (3 super classes) Super Class A. Mastigophora (Flagellate) 2 classes 1. Phytomastigophora (Phytoflagellata), 2. Zoomastigophora (Zooflagellata) Super Class B. Opalinata Super Class C. Sarcodina (Rhizopoda) 03 classes Class 1. Rhizopodea, 3 subclasses Sub class (a) Lobosia, Sub class (b) Filosia, Sub class © Granuloreticulosia Class 2. Actinopodea, 4 sub class Sub Class a. Heliozoia, Sub Class b. Radiolaria Sub Class c. Acantharia, Sub Class d. Proteomyxidia Class 3. Piroplasmea Sub phylum I. Sarcomastigophora Locomotor organelles pseudopodia or flagella or both. Nuclei of one kind (monomorphic). This subphylum has 03- Super Classes 1 Unit I Super Class A. Mastigophora (Flagellate) Simple, primitive, with firm pellicle (protozoan body wall composed of cell membrane, cytoskeleton and other organelles). Locomotor organelles flagella. Nutrition autotrophic or heterotrophic or both. It has got 02 classes 1. Phytomastigophora (Phytoflagellata) Chlorophyll bearing chromotophores present. Nutrition mainly holophytic by phototrophy. Reserve food starch or paramylon. Flagella 1or 2, sometimes more. This class is divided into 08 orders bearing following popular species Euglena. Volvox, Chlamydomonas etc. 2. Zoomastigophora (Zooflagellata) Chlorophyll or chromatophores absent. Mostly parasitic. Nutrition holozoic or saprozoic. Reserve food glycogen. Flagella one to many. It is divided into 09 orders bearing well known species like Trypanosome, Leishmania. Trichomonas, Giardia etc. Super Class B. Opalinata Entire body covered by cilia like flagella. Nuclie 02 to many, monomorphic. Reproduction by symmetrogenic binary fission or by syngamy of anisogametes. Parasitic mainly in frogs and toads eg. Opalina, Zelleriella Super Class C. Sarcodina (Rhizopoda) Body mostly amoeboid without definite pellicle, some with a skeleton of some kind. 2 Unit I Locomotion by pseudopodia. Nutrition holozoic or saprozoic. This Super Class has 03 classes. Class 1. Rhizopodea Pseudopodia as Lobopodia, Filopodia or Reticulopodia, without axial filament. They are generally creeping forms This Class has 03 Sub Classes Sub class (a) Lobosia Pseudopodia as lobopodia Eg., Amoeba, Entamoeba. Pelomyxa, Arcella, Euglypha, Sub class (b) Filosia Pseudopodia as Filopodia. Naked or with a shell with single aperture. eg, Allogromia, Penardia (naked) Sub class © Granuloreticulosia Pseudopodia delicate granular reticulopodia eg, Elphidium. Class 2. Actinopodea Pseudopodia mainly axopodia with axial filament radiating from a spherical body It has 04 Sub Classes Sub Class a. Heliozoia Spherical protozoans called sun-animalcules Pseudopodia (axopodia) radiating. Naked or skeleton of siliceous scales or spines eg, Actinophrys, Actinosphaerium Sub Class b. Radiolaria Body naked or with perforated chitinoid central capsule separating ectoplasm from endoplasm. 3 Unit I Reticulopodia, axopodia or filopodia Skeleton mostly of silicious spicules or of strontium sulphate Eg. Collozoum, Thalassicola Sub Class c. Acantharia Imperforate non chitinoid central capsule without pores Skeleton of strontium sulphate Pseudopodia are axopodia Eg, Acanthometra Sub Class d. Proteomyxidia Pseudopodia are filopodia Mostly parasites on algae Eg. Vampyrella, Pseudospora Class 3. Piroplasmea Small round, rod shaped or amoboid parasites in red blood cells of vertebrates eg. Babesia (formely included with sporozoa but its species do not produce spores) Note Axopodia: fine needle like pseudopodia that contains a central bundle of microtubules Filopodia: pseudopodia that is slender, clear and sometimes branched Lobopodium: pseudopodia that is rather wide with round or blunt tips is commonly tubular and is composed of both ecto and endoplasm Reticulopodium: pseudopodium that forms thread like branched mesh and contain axial microtubules. Axial filament contractile element in the tail of sperm 4 Unit I Brief out line of sub phylum Sporozoa Subphylum II Sporozoa 03 classes Class 1. Telosporea 02- sub classes Sub class (a) Gregarinia Sub class (b) Coccidian Class 2. Toxoplasmea Class 3. Haplosporea Subphylum II Sporozoa Locomotor organelles absent. Spores usually present. Exclusively endoparasites and incapable of active life outside their hosts. Cilia or flagella may be present in gametes. Asexual reproduction by multiple fission and sexual by syngamy. 03 classes Class 1. Telosporea Spores without polar capsules and filaments naked or encysted. Locomotion by gliding or body flexion due to absence of pseudopodia. Adult trophozoites with one nucleus. Reproduction both sexual and asexual. Eg; Monocystis, Plasmodium, Eimeria 02- sub classes . Sub class (a) Gregarinia Mature trophozoites large, extracellular in hosts gut and body cavities. Each spore produces 08 sporozoites. Parasites of invertebrates. Eg; Monocystis, Gregarina . Sub class (b) Coccidian Mature trophozoites small and intracellular. Each oocyst produces many sporozoites. Blood or gut parasites of vertebrates. 1 Unit I Eg; Eimeria, Isospora. Plasmodium Class 2. Toxoplasmea Spores absent. Only asexual reproduction by binary fission. No flagella or pseudopodia at any stage. Cysts with many naked sporozoites. Eg. Toxoplasma, Sarcocystis. Class 3. Haplosporea Spore case present. Only asexual reproduction and shizogony takes place. Flagella absent but pseudopodia may be present. Parasites of fish and invertebrates. Eg; Ichthyosporidium, Haplosporidium. Brief outline of sub phylum Cnidospora Sub phylum III Cnidospora 2 classes Class 1. Myxosporidea Class 2. Microsporidia Sub phylum III Cnidospora Spore formation occurs
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