Nematoda Pseudocoelomates Common Characteristics Pseudocoel Mesoderm muscle lined

Nematoda

Pseudocoelomates

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 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