Phylum Nematoda

RoundwormsMeans “Thread”

                                                    

Aaugh! They are Everywhere! Every fist-full of dirt Every rotten apple Each square meter of lake

bottom Most are free living Most are parasites

Nematooooda! One study in Colorado estimated that

nematodes consumed about as much grass as a prairie dog colony.

Characteristics Tough outer covering- Cuticle No circular muscles- run lengthwise

(move with a crazy thrusting movement) Smooth, round, nonsegmented Tube within a tube Separate sexes 15,000 known species

Muscle Diagram

Examples

Hookworm- Sucks blood in

intestine Enters between the

toes by boring in the skin

Filaria Causes Elephantiasis Transfer by mosquito

Trichinella Causes trichinosis Found in pork

Pinworm Common among children Intense rectal itching Worms are visible near the anus at night

or early in the morning

Horsehair Worm Parasites on

grasshoppers, crickets, locusts, katydids, and beetles

Other hosts include dragonflies, spiders, millipedes, centipedes, and leeches

Persistent Many nematodes are able to suspend

their life processes completely when conditions become unfavorable; in these resistant states they can survive extreme drying, heat, or cold, and then return to life when favorable conditions return.