Notes on roundworm classification and characteristics.

1. Nematoda
roundworms

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

5. Reproduction
Usually diecious - sexes distinct

 parenthogenesis common - asexual
form of reproduction where embryo
grows and develops without fertilization
by a male.

6. Nematode adult anatomy

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

9. Nematode Diets and Mouths

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


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

13. Ascaris Life Cycle

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


15. Dog Heartworm

16. Other Parasitic Nematodes
•hookworm, pinworm, trichinosis,
river blindness, etc.
•cuticle protects against immune
system and enzymes
•can do without oxygen

17. Hookworm: Necator Americanus

18. Dog Hookworm Lifecycle

19. Trichinella: Trichina worm

20. Pinworm: Enterobius

21. Wucharia: Filial worms