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Osteichthyes (a.k.a. “Bony Fish”)

Osteichthyes (a.k.a. “Bony Fish”). Class Osteichthyes. Largest number of species of all classes of vertebrates, more than 23,500 species. Cold-blooded Bony fishes share several distinguishing features:

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Osteichthyes (a.k.a. “Bony Fish”)

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  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 - 550 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.

  8. Physical Characteristics Body Shape:

  9. 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.

  10. Fusiform Body Shape

  11. 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.

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

  13. 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.

  14. External Anatomy • Highly maneuverable fins supported by bone rays.

  15. 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.

  16. Fins • Dorsal finsprevent rolling, used for stabilization • Pectoral finshelp steer, scull backwards • Pelvic finshelp in stopping quickly, aid in stabilizing • Anal finsprotect uro-genital area (often have spines), further stabilize • Caudal fin for propulsion (tail)

  17. 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.

  18. Fin DesignsMouth Shapes

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

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

  21. 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.

  22. 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”.

  23. 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.

  24. 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.

  25. 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”

  26. Counter Shading

  27. Coloration: Cryptic, Countershading?

  28. Spines, Barbles and Lures

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