Fish Vertebrate Success In Water PDF

THE FISHES: VERTEBRATE SUCCESS IN WATER  Infraphylum Hyperotreti: Class Myxini 1. Hagfishes (Gr. myxa, slime) 2. Characteristics. Cartilaginous head support, lack of vertebrae, presence of notochord, sensory tentacles around the mouth, and ventrolateral slime glands. 3. Habitat. Cold-water marine...

THE FISHES: VERTEBRATE SUCCESS IN WATER  Infraphylum Hyperotreti: Class Myxini 1. Hagfishes (Gr. myxa, slime) 2. Characteristics. Cartilaginous head support, lack of vertebrae, presence of notochord, sensory tentacles around the mouth, and ventrolateral slime glands. 3. Habitat. Cold-water marine environments in both hemispheres. 4. Feeding behavior. Scavengers of soft-bodied invertebrates and dead fish. 5. Conservation: Some species endangered due to overfishing for their skin. Class Petromyzontida () Gr. petra, rock + myzo, suckle + odontos, teeth) 1. Lampreys. The mouth is suckerlike and surround by lips that have sensory and attachment functions, epidermal teeth line line the mouth and has a movable tongue. 2. Adults attach to prey with lips and teeth and use the tongue to rasp away scales. 3. Salivary glands have anticoagulant secretions and feed mainly on the blood of their prey. 4. Reproductive. Female attaches nest to a stone using her mouth while the male attaches to female's head and wraps around her. The eggs shed in small batches over several hours; fertilization is external, the sticky eggs covered with sand. Classes of Gnathostomes 1. Three living classes: a. Cartilaginous fishes (Class Chondrichthyes) b. Bony fishes (Classes Actinopterygii and Sarcopterygii) 2. Extinct classes: a. Armored fishes (placoderms) and acanthodians. Evolution of Jaws and Paired Appendages 1. Jaws evolved from anterior pharyngeal arches, enhancing gill ventilation and feeding efficiency. Paired appendages allowed for improved locomotion and stability in early fishes. 2. Evolution of jaws and appendages contributed to predatory lifestyles and adaptive radiation of fishes. Class Chondrichthyes (Gr. chondros, cartilage + ichthyos, fish) 1. Includes sharks, skates, rays, and ratfishes. 2. Most are carnivores or scavengers, primarily marine. 3. Characteristics. Placoid scales and cartilaginous endoskeleton. 4. Teeth are modified placoid scales attached to the jaw cartilage inside the mouth. As outer teeth wear out, newer teeth move in the position from inside the jaw and replace them. 5. Skates and rays. Inhabit the shallow water, has blunt teeth and feed in invertebrates. Tail modified into a defensive lash, and has venomous spine formed from modified placoid scales. Pectoral Fins a. Expanded into winglike appendages. b. Locomotion through muscular waves along fins. c. Camouflage through elaborate dorsal color patterns. (stingray) Bony Fishes or Osteichthyes General Characteristics a. Skeleton contains bone and/or scales (cycloid). b. Bony operculum covering gill openings. c. Presence of lungs (lungfishes) or swim bladder (regulate bouyancy). Class Sarcopterygii (Lobed-Finned Fishes) 1. Characteristics a. Muscular lobes associated with fins. b. Use of lungs for gas exchange. 2. Lungfishes. Ability to breathe air, they can remain in aestivation (the ability to stay dormant that help withstand hot and drey seasons by burrowing in the mud) Related Classes of Fish 1. Hagfishes (Class Myxini). Marine scavengers with pharyngeal slits and slime glands. 2. Lampreys (Class Petromyzontida). Predatory adults with sucking mouths and rasping tongues. 3. Gnathostomes. Possess jaws and paired appendages. 4. Chondrichthyes (Sharks, Skates, Rays). Cartilaginous endoskeleton and placoid scales. 5. Bony Fishes. Has bony skeleton. Evolutionary Pressures on Fishes A. Locomotion 1. Streamlined body shape and mucous secretions (lubricate the body surface) reduce water resistance. 3. Use of fins (vertical caudal fin that thin and forked) and body wall for propulsion. 4. Muscle arrangement in fishes enhances swimming efficiency. 5. Characteristics of fast-swimming fishes (e.g., tuna, mackerel). Nutrition and the Digestive System 1. Early fishes as filter feeders and scavengers. 2. Evolution of jaws leading to predatory behavior. 4. Feeding strategies. Predation. Filter feeding. Herbivory. 5. Structure of the fish digestive tract: stomach and small intestine functions. 6. Gill rakers. Long gill processes that trap plankton while the fish open its mouth and swims through the water.  Circulation and Gas Exchange 1. Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. 2. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments (lamelae) supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. 3. The circulatory (closed circulatory system), or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. 4. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. 5. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and Swim bladder and Lungs 1. Pneumatic sacs. Functioned as lungs, pneumatic sacs function as lungs.