ASCHELMINTHES (I): Overview (Aschelminthes study images;
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a) triploblastic organization (extensive mesoderm)*
b) complete gut (7 of 8 phyla)
c) small size (most < 5 mm; some as small as protists) associated with:
a) it differs little from a hemocoel anatomically (partial or no epithelium separating fluid from tissues)
b) it develops like a hemocoel in other protostomes (separation of connective tissue) except the gut is often free of mesodermal tissue
c) it is not associated with a pumping heart and thus functions mainly as a hydrostatic skeleton; in larger species it likely aids circulation
a) as a skeleton it may antagonize longitudinal muscles
b) it lines the pharynx in many forms and may give rise to teeth or spines important in locomotion or feeding
c) in some groups it is quite tough and must be molted to grow (many nematodes, nematomorphs, and 3 minor phyla)
Copyright (c) 2007 by A. Richard Palmer. All rights reserved.
(revised Jan. 28, 2007)