ASCHELMINTHES (I): Overview (Aschelminthes study images;
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a) triploblastic organization (extensive mesoderm)*
b) complete gut (6 of 8 phyla)
c) small size (most < 5 mm; some as small as protists) associated with:
a) differs little from a hemocoel anatomically (partial or no epithelium separating fluid from tissues)
b) develops like a hemocoel in other protostomes except the gut is often free of mesodermal tissue
c) not associated with a pumping heart and thus functions mainly as a hydrostatic skeleton; in larger species it likely aids circulation
a) thin and flexible in some (e.g., rotifers), it is tough and must be molted to grow in others (many nematodes, nematomorphs, and 3 minor phyla)
b) when thin, it is associated with circular and longitudinal muscles, when thick it may antagonize longitudinal muscles
c) it lines the pharynx in many forms and may give rise to teeth around the mouth or body spines important in locomotion or feeding
Copyright (c) 2017 by A. Richard Palmer. All rights reserved.
(revised Dec. 19, 2016)