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The World of Nematodes

The World of Nematodes. Lecture I Introduction to Nematodes. Nematodes nema = thread; oides = resembling. Nematode Habitats.

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The World of Nematodes

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  1. The World of Nematodes Walia CCSHAU

  2. Lecture I Introduction to Nematodes Walia CCSHAU

  3. Nematodesnema= thread; oides = resembling Walia CCSHAU

  4. Nematode Habitats “If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable….. we would find its mountains, hills, valleys, rivers, lakes and oceans represented by a film of nematodes” ………………N. A. Cobb Nematodes dwell in all types of habitats on earth – from ocean depths to tops of mountains, from hot water springs to icy arctic and antarctic, from barren lands to cultivated fields , and from meadows to tropical forests. Nematodes occupy any conceivable habitat on this earth Walia CCSHAU

  5. Placement in Animal Kingdom • Invertebrates • Protozoa • Porifera • Coelenterata • Platyhelminthes • Aschelminthes • Arthropoda • Annelida • Mollusca • Echinodermata • Vertebrates • Pisces • Amphibia • Reptilia • Aves • Mammalia Walia CCSHAU

  6. The Helminths • Platyhelminthes • Trematodes • Flat worms • Liver fluke, e.g., Fasciola hepatica • Cestodes • Tape worms • e.g., Taeniasolium • Aschelminthes / Nemathelminthes • Nematoda • Rotifera • Priapulida • Gastrotricha • Kinorhyncha • Nematomorpha Walia CCSHAU

  7. Current status • Phylum Nematoda or Nemata • Contains exclusively Nematodes • Nematodes are numerically most abundant among all the metazoans on earth • Nematodes rank second (next to insects) in terms of number of species (diversity of forms). About 25000 species are known till date, out of an estimated 500000 species of nematodes Walia CCSHAU

  8. Types of Nematodes Walia CCSHAU

  9. Relative abundance Walia CCSHAU

  10. Free living nematodes Not economically important, Microscopic, Saprophagous, Microbivorous, Omnipresent – Terrestrial, Aquatic (Marine, Fresh water) Marine nematodes Chromadora Chaetostoma Deontostoma Soil & Fresh Water nematodes Rhabditis Plectus Dorylaimus Nygolaimus Mononchus Walia CCSHAU

  11. Nematodes as Biological Models Free-living bacterial feeder rhabditid nematodes are used as model systems in diverse scientific fields Examples: Caenorhabditiselegans, C. briggsae, Turbatrixaceti, Panagrellusredivivus Applications • Genetics • Developmental Biology • Nutrition • Environmental toxicology • Pharmacology • Gerontology Walia CCSHAU

  12. Advantages of using nematodes as model systems • Axenic and monoaxenic cultivation possible • Adult hermaphrodite (self fertilizing) • Short generation time (ca. 3 days) • Large progeny (300 per individual) • Small size (1 mm long) • Transparent body wall • Storage in liquid nitrogen possible • Handling large number of individuals in a reasonable space • Ease of genetic manipulation (induced mutation) Walia CCSHAU

  13. Applications in Genetics Characteristics of C. elegans • Small genome size (haploid DNA content 8x107 base pairs) • Populations are driven to homozygosity, easy to isolate clones of isogenic animals • New mutants automatically made homozygous in one generation • Mutant stocks readily established from single individual • Mutants are fertile Walia CCSHAU

  14. Mutants Mutants cloned, classified and assigned a code name e.g., “Dpy- 45 (e 420) II” . The code name includes A mutant namee 420 where e is the lab code to trace its origin, 420 is one of the series of mutants from that lab. A gene namedpy- 45, where dpy (dumpy) is phenotypic category and 45 one of the genes in that category A linkage group -II Caenorhabditis Genetic Center National Institute of Aging, Univ. of Missouri, Columbia, USA responsible for maintenance of C. elegansgenetic map, genetic nomenclature, storage, distribution of mutants Walia CCSHAU

  15. PARASITES On Human Beings On Vertebrates On Invertebrates On Plants Medical Sciences Veterinary Sciences Agricultural Sciences Agricultural Sciences NEMATODES AS PARASITES Walia CCSHAU

  16. NEMATODE PARASITE S Of HUMAN BEINGS • Known since ancient times – mention of human parasites in Vedas, first to be recorded • Big in size, easily visible • Examples: • Intestinal round worm Ascarislumbricoides • Pin worm Enterobiusvermicularis • Filarial worm Wucherariabancrofti • Hook worms Ancylostomaduodenale, Necatoramericanus • Guinea worm Dracunculusmedinensis Walia CCSHAU

  17. NEMATODE PARASITE S Of HUMAN BEINGS Ascarislumbricoides -The Intestinal roundworm - Approx 25% world population is infected with Ascaris - Each female lays ca. 2.7 million eggs per day in faeces - Causes anemia and leads to intestinal blockage Walia CCSHAU

  18. NEMATODE PARASITE S Of HUMAN BEINGS Enterobiusvermicularis • Commonly known as Pin worm • Parasite of caecum • Cause itching in anal area Walia CCSHAU

  19. NEMATODE PARASITES Of HUMAN BEINGS Dranunculusmedinensis • Commonly known as Guinea worm • It is a parasite of sub-cutaneous tissues • Ca. 50 million people in Africa and Asia are infected with this nematode Guinea worm forming blisters on the limb Guinea worm partially emerging out of the blister Walia CCSHAU

  20. NEMATODE PARASITES Of HUMAN BEINGS Wucherariabancrofti - The filarial worm Causes Elephantiasis/Filariasis • Parasite of lymphatic system • Causes inflammation of limbs and genital organs • Prevalent in coastal areas of south and east India • Transmitted by mosquitoes Walia CCSHAU

  21. NEMATODE PARASITE S Of VERTEBRATES • Big in size and visible to naked eyes • Some forms are common to human beings • Examples • Trichuris sp. – The whip worm • in alimentary canal of dogs, pigs, ruminants • Dioctophyma renale – the giant kidney worm, • in dog, amy reach up to 90 cm • Haemonchus contortus • in alimentary canal of sheep, goat, cattle • Trichostrongylus spp. • in alimentary canal of ruminants, horses, sheep, goats • Ascaridia galli • in intestine of chicken Walia CCSHAU

  22. NEMATODE PARASITE S Of INVERTEBRATES • The Mermithids • Mermis nigrescens – parasite of grasshoppers and locusts • Romanomermis culicovorax – parasite of mosquito larvae Walia CCSHAU

  23. NEMATODE PARASITE S Of INVERTEBRATES • The Entomopathogenic nematodes – EPNs • Used for biological control of insect pests of crops, commercial • formulations available • Kill diverse group of insects • Carry pathogenic bacteria inside, release in insect haemocoel • Bacteria cause septicaemia, insects die within 2-3 days • Examples: • Steinernema spp. carry bacterium Xenorhabdus spp. • Heterorhabditis spp. carry bacterium Photorhabdus spp. Walia CCSHAU

  24. Entomopathogenic Nematodes Walia CCSHAU

  25. NEMATODES AS PARASITES Walia CCSHAU

  26. Nematology • Agricultural Nematology, Plant Nematology, Phytonematology • Branch of Plant Protection, on par with Entomology and Plant Pathology • First PPN discovered on in 1743 • Economic importance of PPNs realized only after 1940s; reasons • Microscopic size of PPNs • Hidden mode of life, either in soil or roots • No clear cut symptoms on plants • Lack of trained personnel Walia CCSHAU

  27. Walia CCSHAU

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