AGNATHA

AGNATHA

1. SKELETAL SYSTEM

   • AXIAL SKELETON
     • VERTEBRAE
       • most support is from notochord
       • absent in myxinoidea
       • petromyzontida have small cartilaginous neural arches
   • SKULL
     • SPLANCHNOCRANIUM
       • paleostylic jaw suspension
         • all arches support the gills
       • cartilaginous
     • CHONDROCRANIUM
       • cartilaginous
       • encases the brain

2. INTEGUMENT

   • EPIDERMIS
     • keratinized epidermal spines for grasping food
     • covered by mucus cuticle
     • unicellular mucus and toxin glands
     • myxinoidea have multicellular slime glands that coat gills of potential predators
   • DERMIS

3. DIGESTIVE SYSTEM

   • BUCCAL CAVITY
   • PHARYNX
     • gill rakers trap food particles
   • ALIMENTARY CANAL

4. RESPIRATORY SYSTEM

5. CIRCULATORY SYSTEM

   • HEART
     • Petromyzontida have bulbus arteriosus
     • Myxinoidea have two hearts
       • Branchial heart: sinus venosus, atrium, ventricle. Pumps blood through ventral aorta to gills
       • Portal heart: pumps blood through hepatic portal vein to liver
   • VESSELS
     • all 6 aortic arches supply the gills with blood

6. NERVOUS SYSTEM

7. MUSCULAR SYSTEM

   • BRANCHIOMERIC
     • muscular pharyngeal pump pumps water over gills
   • HYPOBRANCHIAL
   • AXIAL
   • APPENDICULAR

8. URINARY SYSTEM

   • NEPHRONS
   • OSMOREGULATION
     • myxinoidea are osmoconformers - do not need to osmoregulate
   • GLANDS