1. Phylum Chordata Subphylum Vertebrata
Class Agnatha
“No Jaws”

2. Class Agnatha All species have circular mouth
Lampreys, hagfish, slime eels

3. Characteristics Body is long, slender – no paired fins
No scales – smooth skin with protective coating of mucous
Circular mouth – anterior & ventral
Buccal funnel lined with conical teeth for grasping

4. Characteristics
Notochord – protective flexible cartilaginous endoskeleton
Heart – 2 chambered
Atrium & ventricle – aorta leads to gills
Closed circulatory system – red & white blood cells
Gills paired in pouches off pharynx
Gill slits (7 or more, paired)

5. Characteristics Excretory – kidneys
Digestive – complete, but without stomach
Nervous system – well developed
Dorsal nerve cord with brain – 8 to 10 cranial nerves
Spinal cord branches into nerve net

6. Characteristics Sensory reception
Olfactory sac – smell/taste reception
Eyes & ears – Extent of development varies by species
Lateral line – similar to sharks, aids in equilibrium, senses vibrations in water

7. Characteristics
Reproduction – ovaries & testes present in an individual, HOWEVER:
Gonads of only one sex function, making them dioecious
Oviparous with external fertilization
Most are anadromous (live in salt water, but return to freshwater to spawn)
Aquatic & marine species
Often parasitic, harmful to commercial fishing