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Dr. Kathy S. Williams (email kwilliams@sunstroke.sdsu.edu)
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BODY CAVETIES : PSEUDOCOELOMATES
(Nematoda & Rotifera)
Consider features aiding increased activity
Pseudocoelomates have a pseudocoelom (591, 593, 606-607)
a fluid-filled body cavity that contains organs
but is not formed completely by mesoderm
so is NOT a true coelom.
The pseudocoelom also serves as a very good hydrostatic skeletonExamples: Nematoda (roundworms) & Rotifera (rotifers)
(1011-1012)
Adaptations for life as active predators or parasites of plants & animals
thick cuticle covering
well-developed longitudinal muscles
review features of parasites
reproduction can be by parthenogenesis (914-915)
Example
of roundworm parasites
Not covered in class:
Trichanella spiralis = trichinosis
Worms encyst (make cycts) in muscle tissues
Humans can acquire the nematode by eating
uncooked meat
(muscle) that contains juvenile worms
(especially pork).
Once in human intestine, juveniles grow
to adults and females
burrow into intestinal wall to reproduce.
Juveniles bore through body or move through
lymph system to
form cycts in other organs including skeletal
muscles.
Cysts cause muscle pain and reduced function of infected organs.
All are aquatic (mostly freshwater) & very active
so small that they dont need many complex organs
unusual
reproduction allows survival in tough times
(parthenogenesis & producing resistant zygotes)
FOR REVIEW
Note that you may be quizzed or examined on items not covered on this list. In general, consider the exercises as "guides" to specific topics considered important. For example, you might try to construct your own questions about a topic, then answer them, to deepen your understanding. You will need to know more than just the following to get do well in this course consider these exercises as a study guide. Contact Dr. Williams or your TA for help.
By now you should be able to do the following (in a half-page or less):
Distinguish between acoelomate and pseudocoelomate. List characteristics of phylum Nematoda that distinguish it from other
pseudocoelomates. Explain similarities and differences among flatworms and roundworms. Give examples of both parasitic & free-living nematodes. Tell what we call a coelom lined by mesoderm(outside) and endoderm
(inside). Discuss significance of having 2 separate openings in digestive tract. Explain advantages of a body cavity being present in an animal. Name 2 taxa that have a hydrostatic skeleton. Name one adaptation (i.e., novel or modified character/feature) thats
typical of parasites.