PHYLUM NEMATODA
Phylum Nematoda
 12,000 species
 500,000 possible
 Cylindrical body
 Only longitudinal muscles
 Non-cellular cuticle with several layers
 Pseudocoelomate
 Mouth and anus
Phylum Nematoda
 Second worm phylum
 More than flatworms
 Think of rubber tubing
 Invertebrates
 Tube-like body tapering to a point
 Roundworms – found everywhere
soil, freshwater, salt water, and in and on other
organisms
wet sand, forest soils, Antarctic sands, and even
pools of super hot water
Physical Characteristics
1. Round, smooth, tube-like
2. Pointed at both ends (taper to a point at
each end)
3. 2 body openings not one (more complex
than flatworms)
2 openings to digestive system
-anterior is the mouth
-posterior is the anus
4. The digestive system is one continuous tube
from mouth to anus (organs float in this
tube)
5. cephalization
Roundworms
Cell / Tissue Structure
1. 3 cell layers: endoderm, mesoderm,
ectoderm = triploblastic
Pseudocoelomates: body cavity not fully
developed
2. Organized cells, tissues, organs, and organ
systems
3. Body round (x-section), covered with cuticle
Locomotion
 Roundworms have a unique way of moving
 Have muscle tissue which runs lengthwise tip
to tip
 As the muscle contract, the tail end and head
end are pulled closer together
 Move like a whip
Digestive System (Food Getting)
 Unlike flatworms have a body cavity and the
organs move in the body cavity (not a true
coelom)
1. 2 body openings (can feed and excrete at
the same time)
2. More efficient than the flatworm
3. Both free living and parasitic (parasites)
Free living
 Role as decomposers in soil
 Digest dead matter and return useful material
to soil
 3 billion in a acre of topsoil
Parasites
 Harmful and harmless
 Harmful
-can cause millions of dollars of crop
damage every year
-hookworm and trichina worm
(trichinosis)
What is Trichinosis?
 Humans
 Eating pork or other meat that is infected
 Pigs take in through infected garbage
 Reproduce in intestines
 Larvae burrow in body of muscle tissue
 Get meat from pig and if not cooked well, the larvae
will not be killed and transfers to the human
 Grows in the intestine
 Causes muscle pain, fever, weakness, and can lead
to death if not treated
Trichinosis Cycle:
Trichinosis continued
Trichinosis
(trichinella worm)
- cysts within the
muscles are consumed
(undercooked food)
-- worm grows in
intestine
-- forms cysts in the
muscles of the new host
-- symptom: terrible pain
in muscles
Nervous and Reproductive System
 Nervous System – simple
 Reproductive System –
1. most are separate sexes
2. sexual reproduction – transfer of egg and
sperm
No Respiratory and Circulatory System
Examples:
*size varies from microscopic to some parasites
1 meter long
1. Ascaris – free living and parasitic
(free living = often beneficial, predators in
the garden)
2. Trichina Worm – parasite (trichinosis)
3. Hookworm - parasite
Roundworms
More parasite pics
Filarial Worms - found in Tropical
regions of Asia
- usually transmitted
by mosquitoes
- causes elephantiasis
Ascarid Worms (common
roundworm)
- lives in intestine
- eggs are passed out in the feces
Most roundworms infect dogs, but
occasionally they find their way into
human hosts
Hookworms
- burrow into the skin from soil
- mature in the intestines
-hooks used to attach and suck blood