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Locomotion in Finned Fish

External features-of Tilapia

  • Has streamlined body shape; this reduces resistance against movement and enables it to cut through water easily.
  • Has an inflexible head that enables it to maintain forward thrush.
  • Has scales that overlap and are pointed backwards to allow water pass over the fish without any obstruction.
  • Secretes mucus which covers the body, this reduces friction during movement.
  • Has flexible backbone; this enables the muscles to contract & relax to bring about undulating movement.
  • Possess swim bladder; which provides buoyancy and also helps the fish to adjust it vertical position in relation to depth in water.
  • Possess lateral line system; this enables it to detect vibrations & change of pressure in water thus enabling fish to respond suitably.
  • Well developed fins which are used for maintaining balance, braking & changing direction.
  • Pectoral fins act as pivot around which the fish can turn rapidly
  • Pectoral and pelvic fins control pitching of the fish; upward and downward movement.
  • Unpaired fins (dorsal, anal, and caudal) reduce rolling (rocking from side to side).
  • Caudal fins propel the fish forward and steers the fish while in motion.

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