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