Phylum: Chordata

Agnatha

• 106 known species
• 2 classes
• Lack jaws, internal ossification, scales & paired fins
• Cartilage

Hagfishes

• 20 species – 4 genera
• Marine – Live on sea floor in very high numbers (15,000 in small area)
• Live in cool to cold waters
• Partial cranium, no true vertebrae

External Characteristics

• Eel-like body – light pink to gray coloration
• No fins, except primitive caudal fin
• No scales or bone - cartilage
• Eyes reduced – very good touch & smell
• 200+ Large slime glands along body
• Ring of 4 tentacles around mouth – very sensitive

Circulatory System

• Osmotic equilibrium with sea water
• 3 Accessory hearts & 1 main heart
• Rhythm not coordinated by CNS
• Very low blood pressure

Respiration

• Gills – 5-16
• Most species have a pair of gill slits/nostrils
• Nostril – pharynx – gills-out

Eating/Digestion

• Scavengers & predators (not parasitic)
• Attracted to dead/dying fish – enters via orifice or digs inside eats from inside out
• Diet is mainly marine worms
• Pharynx – esophagus – intestine – cloaca No stomach
• No jaws – tongue with two keratinized rasps
• Low metabolism – eat every 7 months

Reproduction

• Hagfish are born monoecious
• Can differentiate into either male or female based on population demands or season to season
• No larva
• Females outnumber males
• Large yolk-filled eggs, but small numbers of eggs (1” long, tough shell)
• Not well-understood/prize for information

Tying Into Knots

• Allows for staying put against currents
• Cleans off slime (can sneeze to clear nostrils)
• Protects against predators
• Pull on food & assist in getting into carcass