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 vertebrae
2. Nerve Cord/Spinal Cord
• Protected by vertebrae
• Ends at the brain
3. Bilateral Symmetry
4. 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 Jaws
Cartilaginous
Cartilaginous
Movable Jaw with
teeth
Sharks will lose
and replace teeth
throughout their
life
Bony
Body Plan…
Long
Cylindrical
Fusiform in sharks Diverse!
Dorsoventrally flat
in sharks and rays
Shape of tail…
Lack paired fins
One long body
Paired fins
Heterocercal tails
in sharks
Whip-like tails in
rays with
venomous spines
Homocercal
Fin 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 scales
Many bones
Unique
features…
Feed by suction
with the aid of a
round mouth and
rows of teeth
Ventral mouth
5-7 gill slits
Operculum – gill
cover
Swim bladder – gasfilled to aid buoyancy
Examples:
Hagfish
Lamprey
Sharks
Skates
Rays
Coloration
Movement
Feeding
Senses
Reproduction