Jawless fish, also known as Agnatha, are a group of primitive fish that lack jaws and paired fins. They are considered to be one of the earliest vertebrates and are characterized by several distinct features:
Lack of jaws: Unlike most other fish, jawless fish do not have true jaws. Instead, they have a circular, sucker-like mouth that they use to attach themselves to other fish and feed on their blood.
Lack of paired fins: Jawless fish also lack paired fins, which are found in all other fish. Instead, they have a single dorsal fin that runs the length of their body.
Cartilaginous skeleton: Jawless fish have a cartilaginous skeleton, which is similar to the skeleton of sharks and rays.
No scales: Jawless fish do not have scales on their skin, but instead have a slimy, protective coating.
No swim bladder: Jawless fish do not have a swim bladder, which is an air-filled sac that helps other fish control their buoyancy in the water.
Gills: Jawless fish breathe through gills, which are located behind their heads.
No true stomach: Jawless fish have a simple digestive system with no true stomach. Instead, they have a straight tube-like intestine that runs the length of their body.
Some examples of jawless fish include
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