Download Phylum Nematoda: Roundworms





Among the most numerous of animals (more than
a million in a bucket of pond water or garden soil)
Slender, unsegmented, with tapering ends
Most microscopic, but can be more than 1 meter in
length
Free-living or parasitic




Respiration and Circulation occur through
simple diffusion
Some cephalization - simple brain in head
region
Many types have separate males and females
(only some are hermaphroditic)
Fertilization is internal



Live in soil, salt flats, aquatic sediment, and
water (from polar regions to tropics)
Eat microscopic animals, fungi, algae, bacteria,
or detritus (dead leaves)
Have a tube-like digestive system with two
ends: mouth and anus
Source


Although most roundworms are free-living,
the parasitic roundworms are most well known
Examples include Trichinosis-causing
roundworms, filial worms, ascarid worms, and
hookworms

Trichinosis causes
severe pain as the
worms burrow
through the tissues


Filial worms spread
from host to host by
biting insects
(mosquitoes)
Live in blood and
lymph tissues of the
host which may lead
to elephantiasis
(lymph vessels are
blocked by too many
worms)



Ascaris lumbricoides is
found in more than 1
billion people
worldwide, leading to
malnutrition
Live in the intestine
and/or bloodstream of
the host
Ascarid worms may
reach up to 50 cm in
length! (Link to convert
to inches =
http://www.worldwide
metric.com/metcal.htm)



25% of the world’s
population is affected
Found in the soil,
they use their sharp
hooks and teeth to
burrow into the skin
and enter the
bloodstream
They then travel to
the lungs and then to
the small intestine
where they stay as
adults.
Ancylostoma duodenale
Necator americanus

http://www.dpd.cdc.gov/DPDx/HTML/Para
_Health.htm
Please choose from one of the categories below
or from the alphabetical listing at left.