25.3: General Characteristics of Bony Fishes

1. 25.3: General Characteristics of Bony Fishes Describe the 6 general characteristics of bony fishes Compare and contrast three groups of bony fishes Describe how body shape affects fish movement

3. General Characteristics of Bony Fishes • There are more species of bony fishes than of any other single group of vertebrates. • Ranging in size from about 1 centimeter to more than 6 meters long, bony fishes are common in nearly all marine and freshwater habitats.

5. Ocean Sunfish- the largest bony fish

6. Bony fishes have a relatively stiff skeleton reinforced by hard calcium compounds.

7. Like sharks and rays, bony fishes have gills that extract oxygen from the surrounding water. On each side of the head of bony fishes, a protective flap called the operculum (plural, operculi) covers a chamber housing the gills. Movement of the operculum pumps water through the gills and allows the fish to obtain oxygen from the water even when it is not swimming. • Sharks lack operculi, which is why they must swim or use jaw and pharyngeal muscles to continuously pump water over their gills for gas exchange.

9. Like sharks, bony fishes have a lateral line system, a keen sense of smell, and good eyesight. • Flattened, stiff scales made of bone often cover the skin. Glands in the skin secrete a slimy mucus that helps fishes glide more easily through the water. • The "limbs" of fishes include paired front fins and hind fins, which help maneuver their bodies when swimming. • Like sharks and rays, most bony fishes are carnivores. Many species, however, feed on plankton or algae, such as seaweed.

12. Two key internal features of bony fishes are an air sac and a two-chambered heart. • In most fishes, the air sac functions as a "swim bladder," which makes the animal more buoyant. The air sac also aids "hearing" in many fishes by transmitting vibrations to sensory organs.

13. Some fishes, including lungfishes, use their air sacs as respiratory organs that supplement the gills' exchange of gases with the environment.

14. In the two-chambered heart of a bony fish, one chamber (the ventricle) pumps blood to the gills and the other chamber (the atrium) receives blood returning from the entire body. The blood takes up oxygen as it passes through the gills and then unloads that oxygen as it passes through other organs on its way back to the heart. • This single-circuit pathway for blood flow in fishes delivers oxygen to tissues much more slowly than does the more complex circulatory systems of land-dwelling vertebrates such as frogs. But, compared to land-living vertebrates of the same size, fishes require less oxygen because they have a lower rate of metabolism.

15. kingdom- Animal phylum- Chordate subphylum- Vertebrate class… Diversity of Bony Fishes • Until recently, all bony fishes were grouped together in classOsteichthyes. • Most biologists now recognize 3 separate classes of bony fishes: • ray-finned fishes (class Actinopterygii) • lobe-finned fishes (class Actinistia) • lungfishes (class Dipnoi).

17. Lobe-finned fishes and Lungfishes are lumped together for this graph.

18. Ray-Finned Fishes • There are more than 20,000 species of Actinopterygii. Most bony fishes, including trout, bass, perch, and tuna, are ray-finned fishes. • Ray-finned fishes are named for their fins, which consist of webs of skin supported by bony rays or spines. The thin, flexible fins help fishes maneuver while swimming. They are also used by some fishes for defense from predators.

19. Lobe-Finned Fishes • In contrast to the ray-finned fishes, lobe-finned fishes (class Actinistia) have muscular fins supported by stout bones. • Lobe-finned fishes are not common today and are known mainly from the fossil record. Many fossil lobe-finned fishes from the Devonian period (about 400–350 million years ago) were large and apparently lived and fed on the bottom of shallow, freshwater habitats. They may have used their muscular fins to "walk" along the bottom of bodies of water.

21. The only lobe-finned fishes to survive today are the coelacanths (SEE luh kanths). • Coelacanths are found in the deep waters off the coast of Madagascar and Indonesia.

22. Lungfishes • The 3rd class (Dipnoi) of bony fishes are lungfishes. Today, lungfishes can be found on continents in the Southern Hemisphere. They generally inhabit still ponds and swamps. • The air sac of a lungfish branches into two lobes that function as lungs. A network of tiny blood vessels around the lungs take oxygen from the air that the fish gulps in when it comes to the surface of the water. • Lungfishes also have gills that enable the animals to obtain oxygen from water.

23. Three genera of lungfishes (class Dipnoi) live today in the Southern Hemisphere. • They generally inhabit stagnant ponds and swamps. • They can gulp air into lungs connected to the pharynx of the digestive tract to provide oxygen for metabolism. • Lungfishes also have gills, which are the main organs for gas exchange in Australian lungfishes. • When ponds shrink during the dry season, some lungfishes can burrow into the mud and aestivate. • The ancestor of amphibians and all other tetrapods was probably a lungfish from the Devonian, a period when these fishes were dominant predators.

25. 25.3 Online Review • classOsteichthyes 1, 2, 3, 4 • class Actinopterygii 1, 2, 3 • class Actinistia 1, 2 • Coelacanths1, 2, 3 • Ancient Creature of the Deep • Coelacanth Quiz • class Dipnoi 1, 2, 3 • Fish With Fingers Video • Tetrapod Evolution 1, 2, 3 • Fish Quiz

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