1. Agnatha Chondrichthyes Osteichthyes
FISHES
Agnatha
Chondrichthyes
Osteichthyes

2. General Characteristics
Ectothermic
Vertebrates
Have scales
Swim with fins
Almost all exclusively aquatic
Filter oxygen from water over gills

3. Chondrichthyes – Cartilagenous Fish Osteichthyes – Bony Fish
Classes of Fish
Agnatha – Jawless Fish
Chondrichthyes – Cartilagenous Fish
Osteichthyes – Bony Fish

4. What is the name for a person who studies fishes? Ichthyologist
Question #1:
What is the name for a person who studies fishes?
Ichthyologist

5. Early Fish
Earliest - Filter feeders, no jaws, no fins
Ostracoderms – jawless, heavy bony plates
Lobe finned fishes – Coelocanths

6. Fish Anatomy

7. Fins Caudal – propels fish forward Dorsal – stabilizer
Anal – stabilizer
Pectoral – hold fish steady, maneuvering
Pelvic – hold fish steady, maneuvering

8. Scale Types Cycloid – smooth surface, on bony fish
Carp
Salmon
Ctenoid – teeth along ridge (rough to touch), on bony fish
Bass
Bluegill
Perch

9. Ganoid – hard, interlocking, diamond-shaped, on primitive fish
Scale Types
Placoid – Look like tiny teeth, feel like sandpaper, on cartilagenous fish
Sharks
Rays
Ganoid – hard, interlocking, diamond-shaped, on primitive fish
Gar

10. Question #2: What is the purpose of a fish’s scales?
Shield against injury, help to move through the water

11. Maintaining Buoyancy Swim bladder Liver Uses air Most bony fishes
Can be used as a second “lung”
Liver
Uses oil
Sharks
Most sharks must constantly swim to avoid sinking

12. Use fins and body wall to push against water
Locomotion
Use fins and body wall to push against water
Forked tails reduce drag in the water
Muscles in a zig-zag shape
Each contraction moves large parts of the body wall

13. Gills Obtain oxygen Give off carbon dioxide Most have an operculum
Oxygen dropped into circulatory system pumped by 2-chambered heart

14. Gas Exchange Pump ventilation Ram ventilation
Exchange of gases occurs in capillary network in gill lamellae; water and blood flow in opposite directions over lamellae = Countercurrent Exchange

15. Countercurrent Exchange System

16. Excretion and Osmoregulation
Freshwater fishes
never drink
Lots of nephrons
Ions are reabsorbed
Marine fishes
Drink constantly
Less blood is filtered
Water is reabsorbed

17. Limited vision, focus by moving lens back and forth
Senses
Limited vision, focus by moving lens back and forth
Olfactory receptors
Magnetic receptors
Touch

18. Sense (cont.)
Hearing – sound conducted through skull
Lateral line system – senses movement of other organisms around them
Electroreception – sense electrical impulses generated by muscle twitches

19. Reproduction Oviparous (most fish)
Release eggs, young develop outside mom
Ovoviviparous (some cartilaginous fishes)
Eggs remain inside mom
Eggs at a later stage of development before they are released
Viviparous (a few sharks)
Young born alive

20. Class Agnatha Cartilagenous Simplest and oldest vertebrates Jawless
No scales
Scavengers or parasites
Lamprey, hagfish

22. Class Chondrichthyes
Hinged jaw
Paired fins
Scales
Muscles attached to skin, not skeleton
Cartilagenous skeleton

23. Jaws not attached to brain case
Sharks
Jaws not attached to brain case
Can protrude during attack
20 tons per square inch for an 8’ shark
Size varies (few inches to over 40 feet)
Variable body shapes

24. Skates and Rays
Wing-like pectorals
Most live on sea beds
Some have poison spines on backs or tails (stingrays)

25. Class Osteichthyes
Largest group of fishes
Skeleton made of bone and cartilage
Hinged jaws
Paired fins
Hard, protective scales
Covered gills (operculum)

26. Major Groups of Osteichthyes
Subclass Sarcopterygii
Lobe-finned fishes (Coelocanth)
Lungfishes
Subclass Actinopterygii –
Ray-finned fishes
Bass
Tuna
Guppies