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Nematoda
Pseudocoelomates
A coe lom atesE xam p le :
P la tyh e lm in th es
P seu d ocoe lom atesE xam p le :N em atod a
E u coe lom atesE xam p les :
M o llu sca , A rth rop od s , A n n e lid a
D ivis ion P ro tos tom ia
E xam p les :E ch in od erm ata , ch ord a ta
D ivis ion D eu terosom ia
G rad e B ila te ria
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