 |
You will need to have the Real Player installed on your computer to view this video.
|
Most marine vertebrates are streamlined to help them slice through water. Water's resistance acts to slow them down, but it is also the key to their ability to move through it. Most fishes swim by pushing off against the incompressible water around them. Using the large muscles along the back half of their bodies, they press water backward and to the sides, creating a powerful forward thrust. These rhythmic tail thrusts propel them forward in a wonderfully efficient motion.
A fish's body reflects its lifestyle. Some have broad, flexible tails and lots of white muscle tissue for sudden bursts of speed to attack prey or escape danger. Others have stiff, sickle-shaped tails and more red muscle tissue for endurance on long journeys. Fishes that live among rocks, plants or coral rely on their fins for precise, controlled movements. But powerful forward thrusts require the large muscles that move the tail from side to side, with the other fins used mainly for balance, steering and braking.
The flying fish leaps out of the water and glides long distances on its winglike pectoral fins.
The handfish walks along the ocean bottom using its muscular pectoral fins.
The dolphin paddles its tail up and down and undulates vertically, rather than from side to side as all fishes do.
Sea turtles have flat, streamlined shells and winglike legs for swimming.
The sea snake undulates its entire body from head to tail to swim like an eel, using its flattened tail as a paddle.
| 
