Animals II: Platyhemlinthes, Nematoda, & Annelida

Phylum Platyhelminthes: Flatworms


Embryonic Development: Triploblastic Acoelomate Protostome

Circulatory: None; diffusion (their dorsoventrally flattened morphology facilitates this)

Digestive: None/incomplete; Gastrovascular (highly branched)

Nervous: head ganglion, longitudinal nerve cords

Reproduction: hermaphroditic; reproduce sexually and asexually

Clade: Lophotrocazoa

Symmetry: Bilateral symmetry with cephalization

Special Features: Ciliary motion, muscular pharnyx protonephridial excretory system (flame cells), eye spots

Links:

Flatworms: The First Hunter

Flatworm Fact Sheet

Professor McCauley's Flatworms

Phylum Nematoda: Roundworms
Embryonic Development: Triploblastic Psuedocoelomate Protostome (spiral determinate cleavage)

Circulatory: None; diffusion

Digestive: pharnyx attaches directly to non-muscular intestine

Nervous: dorsal and ventral nerve cords

Reproduction: most are dioecious; sexual

Clade: Ecdysozoa

Symmetry:  Bilateral

Special Features: Muscular pharnyx, sinusoidal motion, collagenous cuticle, longitudinal muscle

Phylum Annelida: Segmented Worms




Embryonic Development: Triploblastic Eucoelomate Protostome (spiral determinate) bilaterally symmetrical with varying degrees of cephalization

Circulatory: Closed; dorsal and ventral blood vessels

Digestive: Complete; musclar pharnyx, esophagus, crop, gizzard, intestine

Nervous: Ventral nerve cord

Reproduction: monoecious; seminal vessicles/recepticles

Clade: Lophotrochozoa

Special Features: Segmentation, hydrostatic skeleton, peristalsis, metanepridial excretory, longitudinal/circular muscles

Links:

Video of dissection

Annelid Fact Sheet