- Almost exclusively endoparasitic.
- Bilaterally symmetrical.
- Specialized suckers for attachment to host.
- Flame cells for excretion.
While a few trematodes are exoparasitic, most are endoparasitic.
They are simple organisms with a gastrovascular cavity, flame
cells for excretion and a nervous system with no special sense
organs. One or more well-developed suckers are used to cling
to the host organism. A cuticle-like tegument protects trematodes
from digestive enzymes and antibodies that are present in the
host. The life cycle of these parasites is extremely complicated,
generally involving egg and several larval stages and utilizing
an array of hosts. Reproduction is sexual.
Some Interesting Facts:
- Adult trematodes can release up to 20,000 eggs per day.
- The Schistomatidae cause the disease schistosomiasis. This
disease can effect humans and become very serious.
Some Pertinent Books Found in Lamson Library:
- Marshall, A.J. and W.D. Williams. 1972. Textbook of Zoology:
Invertebrates. NY: American Elsevier.
- Smyth, J.D. 1966. The Physiology of Trematodes. San
Fransico: W.H. Freeman and Company.
- Using either Clonorchis
as an example, draw on a single page as many as the different
stages of the life cycle as can fix and be usable. How do these
stages differ in size? How do they differ in complexity.
- Along the left side of the page make a sketch of a whole
trematode. Along the right side make drawings of selected sections
associated with the different regions of the wholemount. Try
to imagine what the intervening sections might look like that
connect up the ones that you have drawn.
(Neil D. Breault) (Edited by Betty Miller, Spring