1. The Chordates – Phylum Chordata
Three Sub-Phyla
Urochordata – tunicates
Cephalochordata – lancelets
Craniata (Vertebrata)
Marine, no
Backbone, less
Complex than
vertebrates
tunicate
lancelet

2. Characteristics of ALL Chordates
At some time in their development, chordates:
Have nerve cord – dorsal and hollow
Have notochord – flexible, rodlike supporting structure (turns into backbone)
Have gill slits – paired in throat region (seen only in embryo for some chordates)
Have a post-anal tail

3. Urochordata Tunicates (sea squirts)
Free-swimming larva has all of the characteristics of chordates
Sessile, filter feeders as adults. Most structures of chordates have developed into other structures or have degenerated.

4. Cephalochordata Amphioxus – lancelet Label: mouth tentacles gill slits
intestine
dorsal nerve cord
notochord
anus
tail

5. Characteristics of Craniates (Vertebrates)
Anterior part of nerve cord is brain
3 body sections – head, neck and trunk
Tail during some stage of development
Jointed, internal skeleton
2 pairs of appendages
Heart has 2-4 chambers, closed circulatory system
Gas exchange in lungs or gills
Large body cavity called coelom
Skin has 2 or more layers

6. 8 Classes of Craniates (Vertebrates)
Myxini - Hagfishes
Cephalaspidomorphi - Lampreys
Chondrichthyes - Cartilaginous Fishes
Osteichthyes - Bony Fishes
Amphibia
Reptilia
Aves - Birds
Mammalia
lamprey
Hagfish

7. Cephalaspidomorphi Ammocoetes larva Label: Oral hood
External gill openings
Heart
Intestine
Anus
Caudal fin
Brain
Notochord
Spinal cord

8. Cephalaspidomorphi - Lampreys
All species of lampreys spawn in freshwater streams
Eggs hatch releasing small (1cm) Ammocoetes larvae
Ammocoetes burrow in sand or mud in streams and emerge at night to filter feed.
The larval period lasts from 3-7 years.

9. Parasitic lampreys are either marine or freshwater forms.
Parasitic lamprey adults attach themselves with their sucker-like mouths to fish and rasp through flesh and suck body fluids.
To prevent blood clotting, the lampreys inject an anticoagulant into the wound.
When gorged, the lamprey releases itself, often leaving a fatal wound.

10. Parasitic freshwater adults live a year, spawn and then die
Parasitic marine adults may live longer

11. Nonparasitic lampreys do not feed after they emerge as adults
Their GI tract degenerates into a nonfunctional strand of tissue
They die within a few months after they spawn.

12. Internal Anatomy of the Lamprey
Mouth
Teeth
Tongue
Pineal eye complex
Naris
Olfactory sac
Brain
Spinal cord
Intestine
Ovary/testis
Heart
gills