1. Acoelomates & pseudocoelomates
Zoology, 25 February 2008
Donald Winslow
Following Hickman, et al. 2008
Ch. 14 (pp )
Ch.15 (pp )
Ch.18 (pp )

2. Bilateria Bilateral symmetry & cephalization
Phylum Acoelomorpha (diploblastic)
Superphylum Protostomia (triploblastic)
Lophotrochozoa
Acoelomate worms, pseudocoelomate worms
Ecdysozoa
Pseudocoelomate or eucoelomate
Superphylum Deuterostomia (triploblastic)

3. Acoelomate worms Primary bilateral symmetry No coelom
Three germ layers
Organ-system level of organization
Muscles for locomotion & feeding
Excretory system
Phyla Platyhelminthes, Nemertea, etc.

4. Phylum Platyhelminthes
“flatworms”
Free-living & parasitic species
Anterior ganglia, ladder-type NS
Sensory organs
Excretory system
Usually hermaphroditic & outcrossing
Parasitic spp w/ complex life-cycles

5. Phylum Platyhelminthes
Class Turbellaria
Class Trematoda
Class Monogenea
Class Cestoda

6. Other acoelomate phyla
Phylum Acoelomorpha
(Phylum Mesozoa)—not triploblastic
Phylum Nemertea
Phylum Gnathostomulida

7. Lophotrochozoan pseudocoelomates
Phylum Rotifera
Phylum Acanthocephala
Phylum Gastrotricha
Phylum Entoprocta

8. Ecdysozoan Pseudocoelomates
Phylum Nematoda
Phylum Nematomorpha
Phylum Kinorhyncha
Phylum Loricifera
Phylum Priapulida

9. Phylum Nematoda Longitudinal muscles & muscular pharynx
Anterior & posterior nerves, sense organs
Usually separate sexes
Females larger than males
Microscopic eggs
Eutely