Bony Fishes I Characteristics of Bony Fishes formerly

Bony Fishes

I. Characteristics of Bony Fishes (formerly Class Osteichthyes) Bony fishes have the same general characteristics as non-bony fishes, with the following exceptions: A. Bony Skeleton B. All have gills, though some are vestigial C. Bi-lobed Brain – anterior and posterior lobes D. Mostly egg laying – some exceptions; including live bearing, hermaphroditic, and parthenogenetic. E. Most, but not all, have swim bladders. F. Term Osteichthyes no longer considered an acceptable clade by all. (Taxon grouping) they are now divided into different classes and subclasses, but we still use the term to discuss all bony fishes.

A. Classification: Actinopterygii – Ray finned fishes The most numerous of all fishes – Over 33, 500 species are known! Two groups exist : First are the ancient bony fishes, known as nonteleosts, such as gars and bowfins, which have ganoid scales, and sturgeons, which have bony plates. Longnose Gar Bowfin

The second group is the modern bony fishes, also called teleosts. These are the most numerous and successful of all fishes. They have cycloid and ctenoid scales.

Scales found in Teleosts (Modern Bony Fishes)

Anemonefishes: (30 species) These live in mutual symbiosis with anemones and, in captivity, with some soft or large stony polyp corals. Clown Trigger: (40 species) Like most triggers this is a highly predatory carnivore. However, a very few are planktivores.

Sailfin Mollies: Native species found in the brackish waters of the Northern Gulf, including Mississippi. Lionfish: (40 species) Highly invasive fish that can kill three-quarters of a reef's fish population in just five weeks. They have no natural enemies outside of home range and are exploding in population in Florida waters.

Gambusia holbrooki are nature’s mosquito control. They are found right here on campus, but local numbers may be dropping as mosquito spraying continues, poisoning their diets. They are live bearers, producing 5 -100 young. Mandarin Gobies (Dragonets) : These brightly colored fish, maybe the most colorful fish in the sea, feed almost entirely on micro worms and arthropods. Having no swim bladder, their numbers are dropping due to temp changes in their home range.

Seahorses: (54 known species) These live in gentle flowing sea water with heavy grass and/or coral formations. They feed on micro plankton as fry, and mycidae as adults. They are very difficult to keep and breed in captivity. Strangely, the female deposits as many as 2, 000 eggs into the male’s pouch, where his sperm will fertilize them. They take 10 -25 days to hatch. The father cares for them in the pouch, regulating the salinity in the pouch until they are ready to emerge live. He then abandons them. Only 5 / 1, 000 survive to adulthood, which is a fairly high rate among egg laying fishes, due to internal care before birth.

Sea Dragons: These are members of the same family of fishes as the Seahorses. They have similar habits. Their unique structure helps them hide in Sargassum and other seaweeds. Pipefishes are another close relative of Seahorses. They also feed on tiny foods in and around reefs and grass beds. They also brood with the males getting pregnant and bearing live young after their initial development.

Archer Fish: (7 species) these are highly specialized feeders which live in Australasia. They can shoot prey off of branches as high as 10 ft from the surface of the water! I’ve been fortunate to see them in Australia. Swordtails: Live bearing fishes often kept as pets in aquaria. Easy to care for.

Fish Anatomy and Physiology: Fins of a typical bony fish Anterior Dorsal fin Posterior Dorsal fin Operculum Caudal Fin Pectoral Fin Anal Fin Pelvic Fin Lateral line Peduncle

Ray finned fishes and their characteristics 1. The Operculum is a large cartilaginous flap that covers the gills. 2. Most bony fishes have a swim bladder. a. Trout gulp air into their swim bladder through a pneumatic duct. b. All other bony fishes with swim bladders have remarkable network of capillaries known as the rete mirabile. 3. Not all bony fishes have a swim bladder, but most do. (ex. Gobies, Dragonets, Darters)

peduncle Homocercal Caudal Fin 4. Most of the bony fishes have a homocercal caudal fin. 5. Fish swim using trunk and tail muscles, the meatiest section just before the tail is the peduncle. 6. Zig zagged Muscle bands are called myomeres. Strong like triangles in construction. 7. Swimming is more efficient for fishes than flying or walking for other creatures. (less calories) 8. Pectoral fins used for maintaining position or slight movement. 9. Pelvic fins used for directional

10. While MOST bony fishes have a homocercal tail, there are exceptions! One of these exceptions is the group of flying fishes, who have a heterocercal tail, which is used to launch them from the water into the air, during which they glide for well over a hundred yards with their extended pectoral fins.

11. Countercurrent flow of the water through the gills maximizes oxygen contact with the bloodstream.

Feeding in the Fishes 12. 13. 14. 15. The vast majority of fishes are carnivores. The next largest group are herbivores. The smallest group are the filter feeders. Carnivorous luminous feeders have bioluminescent bacteria or chemicals in special organs or sacs. Fishes feed In a variety of ways

Reproduction among Fishes 16. Catadromous fishes live in fresh water and swim to salt water to reproduce. Ex. Eels to Sargasso Sea. 17. Anadromous fishes live in salt water and swim to fresh water to reproduce. Ex. Lampreys, salmon. 18. Dioecious – Most teleosts, (ray-finned) fishes have separate males and females and external fertilization. 19. The vast majority are oviparous 20. Spawning is the process of reproducing in fishes, such as Salmon, who swim up freshwater rivers and streams to reproduce.

Life Cycle of Pacific Salmon

20. Salmon have a hard time getting home to their stream. In addition to bears, fishermen, and eagles, they now face dams from hydroelectric plants, and siltation from deforested mountainsides. Fortunately, one of these problems is being addressed slowly through the creation of fish ladders. Early ones were not so attractive, later efforts have made ladders that look and seem natural.

Reproduction (continued) 21. Salmon actually smell their way home by odor! 22. A few teleosts have internal fertilization, using a modified fin known as a gonopodium. 23. Live bearing is the most efficient method for fertilization. Female gambusia holbrooki without gonopodium. Male gambusia holbrooki with gonopodium

B. Classification: Class Sarcopterygii – Lobe-finned Fishes. (Coelacanths and Lungfishes) 1. Lobe-finned Coelacanths. Two species of Coelacanth have now been described. These fishes have a diphycercal tail structure. 2. The Lungfishes are found only in the following continents and there are only 6 species. The most specialized are in Africa.

The Coelacanth, a lobe finned fish, was thought to have been extinct for over 70 million years. In 1938, one was found in a dredge off the coast of Madagascar. Since then, several more have been caught.

Coelocanth

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