what makes a fish a fish? chapter 8: marine fishes
TRANSCRIPT
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.
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
Senses
Reproduction
