7621 - Laserfiche WebLink

Home Browse Search

FISH STRUCTURE Fish are cold-blooded animals, mean- ing that body temperatures are the same as the water in which they live. Fish breathe through gills, swim by body mo- tion, use fins for maneuvering, and usually have a covering of scales and an outer cover of mucus for protection from exter- nal infection. There are three main groups of fish in the world: the jawless fish; the boneless or cartilaginous fish; and the bony fishes. Bony fish are those with an internal skel- eton. Only bony fish are found in Col- orado. Jawless fish, an example of which are lampreys, and boneless fish-sharks and rays-are not found within the state. The bony fish are further subdivided into soft-rayed fish and spiny-rayed fish. Cat- fish (despite their spines), trout, pike, minnows and suckers are soft-rayed fish, meaning their fins are supported by soft rays. Catfish spines are different in struc- ture than those of the spiny-rayed fish. Spiny-rayed fish-bass, perch, sunfish, etc.-have at least some fins supported by sharp, stiff spines. To obtain oxygen, fish pass water over the gills, which are made of a fine capil- lary system of very thin-walled blood vessels. These walls are so thin that oxygen can pass into the blood from the water while the carbon dioxide waste is expelled into the water. To breathe in, fish close their gill covers, expand their cheeks and open their mouth. Water flows in over gills. To breathe out, the mouth is closed, cheeks are contracted and gill covers opened. Water flows out, away from the gills. The skin of fish is composed of two layers. The outer layer is called the epider- mis, while the inner layer is the dermis. The thin, outer layer contains many pig- ment cells which form the color pattern, and many mucus cells. These single-celled mucus glands produce the mucus which protects the fish from external infection. The inner, or dermis, layer is thicker and produces the scales. Trout and salmon GENERAL CHARACTERS Commonly Used in Identifying Fish 11. Fin spine 2. Lower jaw (dentary bone) 12. Soft dorsal ftn 3. Barbel 13. Fin ray 4. Nostril 14. Adipose fin 5. Eye 15. Caudal fin 6. Cheek 16. Anal fin 7. Gill cover 17. Anal spine 8. Pectoral fn 18. Lateral line scales 9. Pelvic fin 19. Lateral line Colorado's Little Fish 1. Upper jaw (premaxillary and 10. Spiny dorsal fin maxillary bones)