Phylum Protozoa

Phylum Protozoa Protos — first, Zoan — animal, First animal phylum Study of protozoans called Protozoology Father of protozoology — Antony von Leeuwenhoek Term Protozoa was assigned by Goldfuss Protozoa belong to Kingdom Protista of Haeckel Single-celled, solitary or colonial, eukaryotes Important characters Size ranges from 1µ to 5000µ Aquatic — freshwater or marine forms, or endoparasites Grade of organization- protoplasmic or subcellular Locomotion by cilia, flagella or pseudopodia, or absent Skeleton — may or may not be present; if present then either calcareous or siliceous. Foraminifers have external shell of CaCO3 ( ex. Polystomella), whereas Radiolarians have internal plates of silica Osmoregulation by contractile vacuole in freshwater protozoans (isotonic to 0.8 % NaCl solution). C.V. absent in parasitic and most of the marine forms. Symmetry — radial, bilateral or absent (asymmetrical) Nutrition — Holozoic or holophytic. Digestion intracellular within food vacuole. Reserve food material- Glycogen or Starchlike bodies Respiration — exchange of gases occurs through plasma membrane Excretion –excretory product NH3 (Ammonotelic). Excretion occurs through general body surface or plasmalemma. Blood and nervous tissue absent. Sensory structure stigma (eyespot) present in Euglena Reproduction — Asexual or Sexual. Asexual by budding, spore formation, binary fission or multiple fission. Sexual by Conjugation (Paramecium) or gamete formation (Plasmodium) Euglena Trypanosoma Amoeba Polystomella Paramecium Classification Basis of classification — Locomotory structures 1. Sub Phylum Sarcomastigophora (i) Super Class Mastigophora (Flagellata) — Locomotory structures- flagella Most primitive class Binary fission –longitudinal Two subdivisions- Phytomastigophora and Zoomastigophora Phytomastigophora Zoomastigophora Green Non-green Chloroplast present Chloroplast absent Mostly free living Mostly parasites Reserve food material –starch (paramylon bodies) Reserve food material –Glycogen Flagella- 1 to 2 Flagella 1 to many ex. Euglena, Volvox, Noctiluca and Ceratium Noctiluca –shows bioluminescence, called Burning of sea ex. Trypanosoma , Leishmania , Giardia, Trichomonas, Trichonympha, Proterospongia, Mastigamoeba T. brucei — digenetic parasite, primary host-cattle and secondary host — a fly; Disease-Nagana T. cruzi — digenetic parasite, primary host- man and secondary host — dipteran fly; Disease- Chagas T.evansi — digenetic parasite, primary host –horse and secondary host — Horsefly (Tabanus); Disease- Surra (skin disease) Trichomonas — T. tenax aggrevates pyrrhoea, T. vaginalis causes leucorrhoea. Leishmania donovani — a digenetic parasite, primary host- man and secondary host — Sandfly(Phlebotomus); Disease- Kala-azar(Dumdum fever) L. tropica — causes Oriental sore or Skin Leishmaniasis Giardia — a bilaterally symmetrical form, commonly called ‘Grand old man of intestine’; causes Diarrhoea Trichonympha — It is a symbiotic protozoan in the gut of termites, for cellulose digestion. (ii) Super Class Sarcodina (Rhizopoda)- Locomotory structures-Pseudopodia ( false legs) Free living or parasitic forms Includes Heliozoans, foraminifers, radiolarians and amoebids ex. Amoeba, Entamoeba, Polystomella, Arcella, Pelomyxa and Babesia (an RBC parasite, transmitted through tick and causes Texas fever in cattles) Entamoeba histolytia — a monogenetic parasite in colon (large intestine) of man; causes Amoebiasis or Amoebic dysentry. Infective stage — Tetranucleated cyst. Mode of infection — contaminated food and water. E. gingivalis (or buccalis) — a monogenetic parasite in the pockets, between teeth and gums; aggrevates pyrrhoea. Infective stage — Trophozoite. Mode of infection — Mouth to mouth kissing. E. coli — a commensal of colon 2. Subphylum Ciliophora (Class Ciliata) – The biggest and the most advanced class of protozoa Binary fission — Transverse Nuclei dimorphic, Micronucleus- reproductive and Macronucleus- vegetative in function. ex. Paramecium, Vorticella and Rectal ciliates. Rectal ciliates –found in the rectum of frog and toad, include Balantidium, Nyctotherus and Opalina. Opalina has multinucleated condition. (micro- and macronuclei not differentiated). Though the locomotory structures in Opalina are cilia, due to multinucleated condition, it is sometimes included in superclass Opalinata. 3. Subphylum Sporozoa - Locomotory structures absent Members most specialized for parasitic mode of life. Exclusively endoparasites (contractile vacuole absent) ex. Plasmodium, Monocystis and Eimeria Monocystis- endoparasite in the seminal vesicle of earthworms, feeding on sperms Eimeria- causes coccidiosis in poultry birds 4. Subphylum Cnidospora - Spore formation throughout life Spores contain polar capsule and coiled filament for attachment Trophozoite — multinucleated ex. Nosema, Myxidium (Nosema bombysis causes ‘Pebrine’ disease in silkworm, Bombyx mori). The group Metazoa is divided into Parazoa and Eumetazoa. Porifers belong to parazoa as ectoderm in these animals develops from vegetal pole and the endoderm develops from animal pole. In eumetazoans, it is just reverse