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Nematoda Pseudocoelomates Grade Bilateria Division Protostomia Acoelomates Example: Platyhelminthes Pseudocoelomates Example: Nematoda Division Deuterosomia Eucoelomates Examples: Mollusca, Arthropods, Annelida Examples: Echinodermata, chordata Common Characteristics • Pseudocoel – Mesoderm muscle lined ectoderm • Complete digestive tract • Organs are within pseudocoel • Syncytial epidermis with non-living cuticle Coelom Phylum Nematoda • Found everywhere • Use pseudocoel as a hydrostatic skeleton – Collagen cuticle – Longitudinal muscles • Free living and parasites • Dioecious Nematode Body Plan Muscle Structure • Longitudinal muscles – Parallel to ventral and dorsal nerve cords – Muscle cells form processes to associate with nerve cells – Muscles act against the hydrostatic skeleton Muscle/Nerve Structure Digestion and Metabolism • Pharynx – Radial muscles • Intestine – Single cell layer with no muscles – Body movement and ingestion moves food • Parasitic nematodes often lack complete aerobic respiration Nematode Parasites • Ascaris (roundworms) – Found in intestine and lung. • Hookworms – Attach to intestine and suck blood. • Trichina worm – Forms cysts in muscle – Causes trichinosis • Pinworms – Males are haploid, females diploid – Live in large intestine • Filarial worms – Live in lymphatic system Caenorhabditis elegans • Extensively using in genetic and animal development research • Lineage of each cells is know and documented • Whole genome is cloned and sequenced Family Ancylostomidae • Hookworm – Ancylostoma duodenale – Necator americanus – Ancylostoma caninum Ancylostoma cutting “teeth” Necator americanus Ancylostoma caninum Male Copulatory Bursa Ancylostomidae larval forms Rhbaditiform larva Filariform larva *infective form Ancylostomidae Family Ascarididae • Humans – Ascaris lumbricoides • Pigs – Ascaris suum • Cats – Toxocara cati • Dogs – Toxocara canis • Cats and Dogs – Toxocara leonina Ascaris lumbricoides Ascaris Egg Development Toxocara canis Toxocara in situ • Visceral organ migrans in intermediate host (rodent). • Visceral organ migrans in humans is a dead end infection. Toxocara cati • Adults in intestine • Heavy infection can cause intestinal blockage Toxocara cati Toxocara cati Toxocara transmission to young • Toxocara cati – transmammary route to kittens. • Toxocara canis – transplacental to fetus and transmammary route to puppies. Strongyloides sterocoralis • Homogonic cycle – Female is parasitic – Parthenogenesis • Heterogonic cycle – Free living worms can mate in soil Strongyloides stercoralis Enterobius vermicularis • Pinworm – – – – Not very pathogenic only discomfort Do not infect dogs or cats Feed on epithelial cells and bacteria in intestine Males are haploid, females diploid Enterobius vermicularis Male and Female Pinworms Flat sided pinworm eggs Dirofilaria immitis • • • • Dog and cat heart worm Transmitted through mosquitoes Most common in dogs Infects heart and lungs Dirofilaria immitis in blood Dirofilaria immitis in heart Wuchereria bancrofti • Causes Elephantitis • Swelling and blockage of lymph ducts cause massive swelling in late stages Trichinella spp. • Domestic cycle – Pigs • Trichinella spiralis • Sylvatic cycle (hunting and eating wild mammals) – Temerate Zone • Trichinella britovi • Trichinella spiralis • Trichinella murrelli – Tropic Zone • Trichinella nelsoni – Arctic Zone • Trichinella nativa Trichinella spiralis Trichinella spiralis in situ Muscle Blood Phylum Acanthocephala • Absorb nutrients through tegument • Infect livestock, dogs and cats • Requires invertebrate intermediate host – For example – beetle grubs are the intermediate host for pig infection • Proboscis – Everts and attaches to intestine