1. Phylum Hemichordata Phylum Chordata
Chapter 7
Phylum Hemichordata
Phylum Chordata

2. Phylum Hemichordata Characteristics:
Rare group, but these worms seem to span a gap between invertebrates and more advanced chordate animals
Acorn worms share some features with chordates including pharnyngeal gill slits and a nerve cord that is similar to the chordate notochord
Acorn worms are deposit or suspension feeders and use proboscis for feeding
Acorn worms have larvae that resemble those seen in echinoderms
90 known species

3. Phylum Cordata (the inverts)
Subphylum Urochordata - tunicates
Subphylum Cephalochordata – lancelets
Chordates have several common features that are seen at least during some portion of the life.
Lancelets are the only chordates that possess all the common features as adults.

4. Phylum Chordata Characteristics:
Notochord – flexible support rod between nerve cord and gut
Tubular nerve cord
Muscular pharynx (gut)
Gill slits
Post-Anal Tail
Ventral heart
Note: no backbone. In vertebrates, notochord is surrounded or replaced by the vertebral column.

5. Invertebrate Chordates Tunicates – Subphylum Urochordata, Class Ascidiacea
Characteristics:
Commonly called “sea squirts” because most filter feed via an incurrent siphon and “squirt” water out an excurrent siphon after the water has been filtered (Exception: Predatory tunicate)
Larvae has chordate characteristics that are not seen in adults- only pharynx remains
Called tunicates because of thick outer covering called a tunic
Larvae are free swimming after fertilization occurs in open water- mass reproduction - see Fig. 7.51
Adults normally live attached to boats, docks, reefs, or other hard substrate
All 3000 known species are marine

6. Tunicates A A B
Figure 7.51 A. Clavelina picta, colonial ascidian. B. tadpole larva of ascidians exhibits all the distinguishing characteristics of chordates.

7. B A
Figure 7.52 A. Cliona intestinalis, shallow water sea squirt. B. Adult tunicate

8. Phylum Chordata Subphylum Cephalochordata, the Lancelets
Characteristics:
23 species
Very small, only up to 3 inches long
Live in shallow marine waters as filter feeders
Body shows segmented muscle tissue
Notochord attached to the muscles
Gills are used to filter food, not in respiration
Only invert chordate to possess all chordate features as an adult

9. Phylum Chordata Subphylum Cephalochordata, the Lancelets

10. Phylogenetic relationships of animal phyla

11. Characteristics of Major Animal Phyla