L20 Jawless fishes Pt 2

What is a “fish”?

All vertebrates that are not tetrapods

What does the lateral line in fish do?

Sense water currents and vibrations

What are the 5 types of fishes

1. Hagfishes

2. Lampreys

3. Cartilaginous fishes

4. Ray-fins

5. Lobe-fins

What does Agnatha mean?

Jawless

What does the monophyletic group Cyclostomata of the jawless fishes include?

• Hagfishes

• Lampreys

What kind of teeth do Cyclostomata (lampreys, hagfishes) have?

Keratin

What class are the hagfishes?

Myxini

The class Myxini (hagfishes) are a part of what superclass?

Cyclostomata

The class Myxini (hagfishes) are a part of what subphylum?

Vertebrata

What differentiates hagfishes from lampreys?

Hagfishes produce copious amounts of slime

Why do hagfishes (Myxini) use slime?

To defend against predators

What is special about hagfishes?

They are the only iso-omotic living vertebrate

What does it mean to be iso-osmotic?

The internal fluid concentrations of salts and water balance is the same as the environment they live in

How do hagfishes eat?

Bottom scavengers

What class are the lampreys?

Petromyzontida

Where do hagfishes have vertebral elements?

In embryo and their tail

Where do lampreys have vertebral elements?

Throughout their body

What type of life cycle do lampreys have?

Anadromous (swim upstream to freshwater to spawn their offspring)

What classes are in the Agnatha (jawless fishes)

• Ostracoderms (extinct)

• Cyclostomata (hagfishes and lampreys)

What are the Gnathostomes?

Jawed animals

Where did jaws originate?

From 2 pairs of endochondral cartilaginous articulated arches

What two pairs of endochondral cartilaginous articulated arches did jaws originate from?

Mandibular and hyoid

What did the mandibular and hyoid arches evolve from during the creation of the jaw?

Gill arches

What is another synapomorphy of the Gnathostomes group (jawed fish)?

Paired fins

What are the two part hypothesis origins of paired fins in Gnathostomes?

1. Finfolds

2. Outgrowths of lateral plate mesoderm

What are the Placoderms?

Armored fishes with jaws (extinct)

What type of skeleton do the Placoderms have? (armored jawed fishes)

Endo and Exoskeleton