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Nematoda, nematomorpha, tardigrada
- 2. Ecdysozoa Protostomes that must shed their cuticle in order to grow - Like the Lophotrochozoa, ecdysozoans do not share a common body plan - Some are pseudocoelomate - Nematoda and Nematomorpha - Some are acoelomate - Some are eucoelomate - Panarthropoda (contains Tardigrada and Arthropoda)
- 5. Phylum Nematoda Diversity - 25,000 named species - Maybe 500,000 - possibly more Distribution - Polar to tropics - Marine, freshwater, and terrestrial “In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites."
- 7. Phylum Nematoda Life Style - Nematodes are parasites of most all plants and animals - Medical, veterinary, and agricultural losses are billion annually - Many are free-living and feed on - Bacteria, - Yeasts, - Fungal hyphae, - Algae - Predatory species may feed on rotifers, tardigrades, small annelids, or other nematodes
- 8. Phylum Nematoda Caenorhabditis elegans - Model for understanding development, gene function, and programmed cell death
- 9. Phylum Nematoda Form and Function - Distinguishing features - Cylindrical shape - Cuticle (collagen) - Secreted by hypodermis - Hypodermal cords - Lack cilia and flagella - Longitudinal body muscles only - Four bands - Hydrostatic skeleton - Eutely
- 10. Phylum Nematoda Form and Function - Distinguishing features - Cylindrical shape - Cuticle (collagen) - Secreted by hypodermis (epidermis) - Hypodermal cords - Lack cilia and flagella - Longitudinal body muscles only - Four bands - Hydrostatic skeleton - Eutely
- 11. Phylum Nematoda Form and Function - Distinguishing features - Cylindrical shape - Cuticle (collagen) - Secreted by hypodermis (epidermis) - Syncytial - Hypodermal cords - Lack cilia and flagella - Longitudinal body muscles only - Four bands - Hydrostatic skeleton - Eutely
- 12. Phylum Nematoda Form and Function - Distinguishing features - Cylindrical shape - Cuticle (collagen) - Secreted by hypodermis (epidermis) - Syncytial - Hypodermal cords - Lack cilia and flagella - Longitudinal body muscles only - Four bands - Hydrostatic skeleton - Eutely
- 13. Phylum Nematoda Form and Function Alimentary canal - Mouth - Muscular pharynx - Non-muscular intestine - Uses pressure of pseudocoelom - Short rectum - Anus - Feces expelled through body pressure
- 14. Phylum Nematoda Form and Function Circulation and Respiration - No dedicated organ systems - Diffusion used
- 15. Phylum Nematoda Form and Function Nervous System - Ring of nervous tissue and ganglia around pharynx - Dorsal and ventral nerve cords - Sensory papillae near head and tail - Amphids on either side of head - Primary sense organ
- 16. Phylum Nematoda Form and Function Reproduction - Most are dioecious - Female larger than male - Fertilization is internal - Development is direct - Cuticle shed after each larval stage
- 17. Phylum Nematoda Representative nematodes Ariscas lumbricoides - Warm, humid regions of the globe - 1+ billion humans may be infected - 30cm in length - 200,000 eggs per day - Shed with feces - Can live in ground for weeks - Find new host through consumption of contaminated food
- 18. Phylum Nematoda Representative nematodes Ariscas lumbricoides
- 19. Phylum Nematoda Representative nematodes Necator americanus - hookworm
- 20. Phylum Nematoda Representative nematodes Parelaphostrongylus tenuis - moose brain worm
- 22. Phylum Nematomorpha Horsehair worms Form and function - Long and slender - 0.5-3mm diameter; up to 1m in length - Body wall is similar to nematodes - Cuticle - Hypodermis - Longitudinal muscles
- 23. Phylum Nematomorpha Horsehair worms Form and function - Long and slender - 0.5-3mm diameter; up to 1m in length - Body wall is similar to nematodes - Cuticle - Hypodermis - Longitudinal muscles
- 24. Phylum Nematomorpha Horsehair worms Form and function - Digestive system - Vestigial - Larval forms absorb all nutrients from hosts - Adults absorb nutrients from the water
- 25. Phylum Nematomorpha Horsehair worms Form and function - Circulatory, respiratory, and excretory systems are lacking - Nervous system is more simple than in Nematoda
- 26. Phylum Nematomorpha Horsehair worms - Reproduction - Dioecious - Adults mate in water and shed fertilized eggs into water - Life cycles poorly known - Gordius - Juvenile nematomorphans encyst on vegetation - May also infect through drinking - Consumed by arthropods - Several months spent in hemocoel - Drive host to water and emerge
- 30. Phylum Tardigrada Water bears or moss piglets General characteristics - < 1mm in length - Approx. 900 species - Mostly terrestrial, but some live in freshwater, and a few are marine - Elongated, cylindrical body; unsegmented
- 31. Phylum Tardigrada Water bears or moss piglets General characteristics - Head poorly defined - Four pairs of unjointed legs - Claws present - Cuticle present and molted
- 32. Phylum Tardigrada Water bears or moss piglets General characteristics - Mouth as buccal tube with associated pharynx - Adapted for sucking - Needle-like stylets present - Pierce cells of plants/animals
- 33. Phylum Tardigrada Water bears or moss piglets General characteristics - Most of body is hemocoel - True coelom restricted to gonadal cavity - No circulatory or respiratory system - All gas exchange via diffusion
- 34. Phylum Tardigrada Water bears or moss piglets Reproduction - Dioecious - Some species males are unknown; parthenogenesis - Egg laying occurs when cuticle is shed - Direct development
- 35. Phylum Tardigrada Water bears or moss piglets Hard to kill - Diapause (encystment) - internal physiological mechanism - Cuticle shed, and then replaced by several layers of simpler cuticle - Lack legs and such. - Quiescence (cryptobiosis) - state or dormancy maintained by environmental factors - Metabolic activities are non-existent - Form a tun - Withdraw legs, and lose much body water
- 37. Phylum Tardigrada Water bears or moss piglets Hard to kill - Cryptobiosis - can survive - Anhydrobiosis - desiccation resistance - Cryobiosis - temperature resistance - Survive for years at -18C, can even survive -196C for a time - Survive up to 151C - Anyoxybiosis - no oxygen - Vacuum - can survive in space - Radiation - Ion radiation that would kill us is shrugged off
Editor's Notes
- Nathan Augustus Cobb, a nematologist working for the U.S. Department of Agriculture, famously put it this way in 1915: