Chordates and Fishes

Notochord

Rod like structure, used for support

Dorsal Nerve Cord

Main nervous system

Pharyngeal Slits

Used for feeding, turns into inner ear in tetrapods

Endostyle

Secretes mucus, turns into thyroid

Postanal tail

Used for propulsion

Tunicate

Sessile, specialized chordate. Common in oceans.

Lancelet

Swimming chordate, feeds with pharyngeal slits

Earliest fish description

Invertebrate, boneless, and jawless

Ostracoderm

Primitive jawless fish with bony plates on head

Placoderm

Large, primitive fish with bony plates and jaws

Living fishes in the Agnatha

Hagfish and Lampreys

How hagfish protect themselves

By producing large amounts of mucus

Lamprey feeding

They are vampiric, sucking body fluids of fishes

What region did lampreys invade?

The great lakes region

Chondrichthyes

Class including sharks, rays, and skates

Difference between skates and rays

Skates have no stinger and short, thick tails; Rays have stingers and long, whip-like tails

How do Chondrichthyes maintain buoyancy?

They have an oily liver

Senses used by sharks

Smell, vision, hearing, sensing electrical impulses

Shark specialized sensory pits

Ampullae of Lorenzini, can detect electricity and magnetic fields

What are shark scales like?

Placoid scales, like teeth embedded in the skin

Shark tails and buoyancy

The heterocercal tail pushes the shark upwards

Shark teeth

Pointy - for eating fish and invertebrates. Triangular - for cutting through the hides of mammals

Shark vs bony fish fins

Shark pectoral fins are on the bottom, bony fish pectoral fins are by the gills; Shark pelvic fins are in the rear, bony fish pelvic fins are under the gills

Muscle color in fish

Fish that continuously swim fast or sprint usually have more red muscle; Fish that swim slowly or live on the bottom typically have more white muscle

Salt regulation in sharks vs bony fish

Sharks have a rectal gland, they just get rid of salt whenever they have to; Bony fish regulate salts by how concentrated their urine is and by pumping salt in or out with chloride cells in their gills.

Holocephali

group that includes chimeras and ratfishes

Batoidea

Group that includes the skates and rays

Galeomorphi

Group that includes the modern sharks

Squalomorphi

Group that includes primitive sharks

Medial fins

Used for stability

Paired fins

Used for turning and stopping

Rounded, thick fish tail

Present on slow, powerful swimmers

Triangular, semi-thick fish tail

Present on sprinting fish

Thin, tall, narrow fish tails

Present on continuous high speed swimmers