Ecological Parasitology

Lab 9: Nematodes Spring 2011

Classification

•  Kingdom: Animalia – Phylum: Nematoda (roundworms, complete

digestive system)- one of largest phyla

General Information

•  Morphology similar among species – Parasitic and free-living! – Large differences in size

•  Numerous and specious –  If earth disappeared but nematodes remained,

you could still see it! – Many undescribed species, one lives only on

beer mug mats in certain bars in Germany!

Morphology

•  No segmentation, smooth body

•  Cuticle with multiple layers (outer layer VERY resistant to chemicals and enzymes)

Morphology

•  Muscles longitudinal only

•  Turgor (positive pressures) used as a “skeleton”

Morphology

•  Nervous system –  Ganglia around

pharynx –  Pits on anterior end

with amphids (chemosensory organs, inconspicuous)

–  Palpillae- touch

Morphology

•  Digestive system –  Mouth- usually with

6 lips –  Buccal cavity –  Esophagus –  Rectum –  Anus

Morphology •  Reproduction

–  Parthenogenetic, hermaphroditic (sometimes sequential), or separate sexes

–  Females larger, two ovaries

–  Males have curved tails, grasping mechanism (bursa) for copulation, one testis, amoeboid sperm

Life Cycle

•  Egg •  Four larval stages •  Adult

http://parasitewonders.blogspot.com/2008_07_01_archive.html

Today’s parasites

•  Dirofilaria immitis •  Enterobius vermicularis •  Ascaris lumbricoides •  Toxocara sp. •  Trichuris trichiura •  Ancylostoma spp. •  Oesophagastomum sp. •  Trichinella spiralis

Dirofilaria immitis

•  Dog heartworm •  Adult in heart, larvae in blood and

mosquito vector

Enterobius vermicularis

•  Pinworm •  Itchy butt •  If in vagina, can cause sterility •  Adults and larvae in humans (and other

animals), eggs in environment (e.g. money)

Ascaris lumbricoides

•  Viscera larval migrans –  Intestinecirculationlungstrachea

pharynxintestine •  Largest nematode of humans

Toxocara sp.

•  In dog feces •  For a while, was a leading cause of

childhood blindness •  Larvae migrate- liver, lungs, brain, etc.

Trichuris trichiura

•  Whip worm •  Can cause prolapsed rectum, usually mild •  Contaminated food/water

Ancylostoma duodenale

•  Hookworm (old world) •  Feeds on villi, viceral larva migrans

Oesophagastomum sp.

•  Free-living and parasitic •  Eggs look like hookworm eggs

Trichinella spiralis

•  Trichinosis- muscle pain •  Larvae in muscles (adults in intestine) •  Get from eating undercooked pork, etc.