Characteristics
Agnatha, meaning "jawless," is a superclass of primitive fish-like vertebrates that lack jaws and paired fins. They are characterized by their smooth, slimy bodies, multiple gill openings, and single dorsal fin. Agnatha is divided into two main classes: Cephalaspidomorphi (lampreys) and Myxini (hagfish).
- Jawless, soft-bodied vertebrates
- Multiple gill openings
- No paired fins
Lampreys: Petromyzontidae
Lampreys, belonging to the Petromyzontidae family, are parasitic or opportunistic feeders with circular mouths lined with teeth. They attach to hosts, using their mouths to siphon blood and bodily fluids. Lampreys have a larval stage called ammocoete, which is filter-feeding and resembles a cephalaspid.
- Parasitic with circular, toothed mouths
- Larval stage called ammocoete
- Primitive vertebrate features
Hagfish: Myxinidae
Hagfish, part of the Myxinidae family, are known for their slime-producing glands and scavenging behavior. They have rudimentary eyes and can Knot their bodies to escape predators. Unlike lampreys, hagfish are not considered true fish due to their lack of vertebral column, though they possess a notochord.
- Scavengers with slime glands
- Notochord but no true vertebral column
- Primitive gill structures