1. Osteichthyes (a.k.a. “Bony Fish”)

2. Class Osteichthyes
Largest number of species of all classes of vertebrates, more than 23,500 species.
Cold-blooded
Bony fishes share several distinguishing features:
a skeleton of bone, scales, paired fins, one pair of gill openings, jaws, and paired nostrils.

3. History
Primitive fishes date back to the Cambrian period million years ago.
The Devonian period (360 to 400 mya) is known as the "Age of Fishes" because of the abundance and diversity of fishes that appear during this period.

4. Crossopterygians
Scientists thought that all Crossopterygians were extinct. In 1938, however, a living member of this group, the coelacanth was discovered off the S. African coast.

5. The Coelacanth
Lobe-finned fishes
Courtesy of Dinofish.com

6. Coelacanth

7. Physical Characteristics
Size:
Largest: Ocean Sunfish (mola- mola)
Smallest: dwarf gobi (0.3 in)
Mola-Mola can get to be 13 ft and weigh 3,300 lbs.

9. Physical Characteristics
Body Shape:

10. Physical Characteristics: Body Shape
Most bony fishes have a fusiform (rounded and tapering at both ends) body shape.
This body shape reduces drag and requires a minimum amount of energy to swim.
Bony fish forms deviate from the fusiform body shape in three directions:
Compression
Depression
Elongation.

11. Fusiform Body Shape

12. Laterally Compressed Body Shape
A laterally compressed body shape is common in bony fishes that live in dense cover or within coral reefs. The compressed body is laterally flattened.

13. Depressed Body Shape
A depressed body shape is common in bottom-dwelling bony fishes.
Examples: Goosefishes, batfishes and flat fishes

14. Elongated Body Shape
Elongated body shapes are common in open ocean fishes and eels.
The elongated body is horizontally lengthened.
The morays eels are good examples of fishes with an elongated body shape. Lamprey.

15. External Anatomy
Highly maneuverable fins supported by bone rays.

16. Fins Fishes have two kinds of fins:
paired fins (pectoral and pelvic)
median fins (dorsal, caudal, and anal)
Except in the lungfishes and the coelacanth, fins lack bones.
Some bony fishes have soft, flexible fin rays.
Other bony fishes have spiny, rigid fin rays.

17. Fins Dorsal fins prevent rolling, used for stabilization
Pectoral fins help steer, scull backwards
Pelvic fins help in stopping quickly, aid in stabilizing
Anal fins protect uro-genital area (often have spines), further stabilize
Caudal fin for propulsion (tail)

18. Caudal Fins
Fishes with truncate or rounded caudal fins are usually strong, but slow, swimmers.
Many continuously swimming fishes have forked caudal fins.
Fishes with lunate caudal fins tend to be the fastest fishes and maintain a rapid speed for long durations.

19. Fin Designs Mouth Shapes

20. Skeletal Structure
Complex bony skeleton composed of spines (in fins), ribs and vertebrae.

21. Cycloid & Ctentoid scales “Denticles” Placoid scales
Body Covering
Cycloid & Ctentoid scales
“Denticles” Placoid scales
Overlapping scales gives the fish greater flexibility

22. Cycloid or Ctenoid Scales
Most bony fishes have cycloid or ctenoid scales.
As they grow, cycloid and ctenoid scales add concentric layers.
Cycloid scales are circular and smooth.
Ctenoid scales have a characteristic toothed edge. They are most common on fishes with spiny fin rays.

23. Placoid Scales
These scales are found on sharks and are really just small teeth that cover the body.
On sharks placoid scales are known as “denticles”.

24. Body Covering Ganoid scales are thick and non-overlapping
and are composed of bone overlaid with an
enamel-like substance called ganoin. These
scales are adapted for protection.

25. Lateral Line
Function: detects the slightest water movements. Also aids in fish schooling.
This special sense organ lies in tiny pits along both sides of the body.

26. Coloration Pigment is mostly contained in cells called chromatophores.
Reflective cells called iridocytes can change color rapidly.
Coloration may serve as camouflage:
Most species of fishes are countershaded.
Some fishes show disruptive coloration, a camouflage in which the color pattern of the animal contradicts the animal's body shape.
Some fishes rely on coloration for species recognition and sexual distinction.
Color warns other fishes:
“I will defend my territory”
“I am poisonous”

27. Counter Shading

28. Coloration: Cryptic, Countershading?

29. Spines, Barbles and Lures