What Makes a Fish a Fish?

Chapter 8:Marine Fishes

Fish are Vertebrates…

1. Backbone – called a vertebral column or spine– Dorsal row of hollow skeletal elements (usually bone)

called vertebrae2. Nerve Cord/Spinal Cord

• Protected by vertebrae• Ends at the brain

3. Bilateral Symmetry4. Endoskeleton

Yellow Perch

What Makes a Fish a Fish?A fish is an organism that…

– is aquatic,– exchanges oxygen using gills,– is covered with scales,– and has paired fins.

Fish Anatomy

A Typical Fish

Background

• Oldest, structurally simplest vertebrates• Most abundant vertebrates

– At least 30,000 species• Phylum: Chordata

– Subphylum: Vertebrata• Class: Agnatha – jawless fishes• Class: Chondrichthyes – sharks, rays, ratfish• Class: Osteicthyes – bony fishes

Characteristic Class Agnatha Class Chondrichthyes

Class Osteichthyes

Skeleton… Lack JawsCartilaginous

CartilaginousMovable Jaw with teethSharks will lose and replace teeth throughout their life

Bony

Body Plan… LongCylindrical

Fusiform in sharksDorsoventrally flat in sharks and rays

Diverse!

Shape of tail… Lack paired finsOne long body

Paired finsHeterocercal tails in sharksWhip-like tails in rays with venomous spines

HomocercalFin rays usually with spines

Characteristic Class Agnatha Class Chondrichthyes

ClassOsteichthyes

Scales… Lack scales Placoid scales (dermal denticles) - covered in enamel like teeth-Pointed tip that points backwards

- Produces rough feeling

Cycloid/Ctenoid scalesMany bones

Unique features…

Feed by suction with the aid of a round mouth and rows of teeth

Ventral mouth5-7 gill slits

Operculum – gill coverSwim bladder – gas-filled to aid buoyancy

Examples: HagfishLamprey

SharksSkatesRays

Coloration

Movement

Feeding

http://upload.wikimedia.org/wikipedia/commons/c/c3/Barracuda_with_prey.jpg

http://upload.wikimedia.org/wikipedia/commons/8/84/Sunfish2.jpg

Senses

Reproduction