2. Characteristics
Free-living or parasitic
Most very small < 2mm, some 1m long
Abundant (100 in a cupful of soil) >20,000
named species, many others undescribed
Radial symmetry - cylindrical body
Pseudocoelomate - false body cavity
Tough cuticle must be shed to grow
Has cephalization
3. Organization
Specialized cells
Organized Tissues
Tripoblastic - 3 cell layers
Organ systems
Muscles - only longitudinal
Reproductive
Digestive - Complete gut w/ mouth and
anus
4.
5. Reproduction
Usually diecious - sexes distinct
parenthogenesis common - asexual
form of reproduction where embryo
grows and develops without fertilization
by a male.
7. Nematode Locomotion
Pressurized pseudocoelom holds shape
Longitudinal muscles that pull against
that pressure to provide a spiral
lashing motion
For burrowing and penetrating host
tissues
8. Feeding Modes of Nematodes
Microbivores - select bacteria and fungi
from soil and water
Predators eat small prey, or pierce and
suck out larger prey
Plant parasites
Animal parasites
10. Classification
Ascaris - Intestinal Roundworm
l
genus Ascaris, females up to 30 cm
67% used to be infected in S.E. United
States
adults eat intestinal chyme
heavy infections cause abdominal pain
and allergic reactions
or death, in heavy infections of children
11.
12. Ascaris Internal Migration
eggs transferred from feces to food or
mouth by hand; hatch in intestine
larvae penetrate bloodstream, go to
lungs
break out into alveoli and crawl up
trachea to esophagus, swallowed again
adults live free in small intestine
14. Dog Heartworm Life Cycle
Adult lives in dog’s heart muscle
releases eggs into bloodstream, which
hatch into small larvae (“microfilariae”)
larvae enter a mosquito that bites the dog
enter another dog by mosquito’s next bite
migrate to heart and grow inside muscle
Dog Heartworm
16. Other Parasitic Nematodes
•hookworm, pinworm, trichinosis,
river blindness, etc.
•cuticle protects against immune
system and enzymes
•can do without oxygen
