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Locomotion of fish

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  1. Locomotion of fish • Streamlined shape and mucoid secretions that lubricate its body surface reduces friction between the water and the fish • Water’s bouyancy properties also contribute to the efficiency of the fishes movement • Fish move through the water using their fins and body wall to push against the incompressible water

  2. Nutrition of fish and digestive system of fish • Earliest fish were probably filter feeders • Modern fish are predators and spend much of their lives searching for food • Usually swallow their food whole • Teeth capture and hold prey • Gill rakers: trap plankton while the fish is swimming through the water with its mouth open • Have a stomach that stores large and infrequent meals • Small intestine is the primary site for enzyme secretion and food digestion • Pyloric ceca-outpockets of the intestine increase absorptive and secretory surfaces

  3. Fish digestive system

  4. Circulation and gas exchange

  5. Gas exchange • To maintain adequate levels of oxygen the fish have to pass large quantities of water over their gills • Ram ventilation: maintain water flow by holding their mouths open while swimming • gas exchange across gill surfaces is very efficient • Countercurrent exchange mechanism

  6. Swim bladders and lungs • Pneumatic sacs: gas chambers • Fish maintain vertical buoyancy by their buoyant oils, the use of fins to provide lift, the reduction of heavy tissues and a swim bladder • Control the amount of gas in the swim bladder to maintain buoyancy

  7. Nervous system and sensory functions • Central nervous system of a fish has a brain and spinal cord • Sensory receptors are present throughout the body • External nares: snout of fish for olfactory receptors • Eyes: lidless and round • Receptors for equilibrium, balance and hearing are in the inner ears • Lateral line system: used to detect either water currents or a predator or a prey that may be causing water movements in the vicinity of the fish

  8. Excretion and osmoregulation • Osmoregulation is maintained by the kidneys and the gills • Nephrons in the kidneys • Use osmotic uptake for water across gill, oral and intestinal surfaces • Excretion and defecation are constant • Most excretion is ammonia • cloaca-opening used for excretion, digestion and reproduction

  9. Dog fish puffer

  10. Parrot Fish

  11. Mexican Walking Fish (amphibous fish)

  12. Hand fish