rm = rete mirabile Sharks:
Controlling Internal Environment
by,
Parker Wingfield
Sharks poikilotherms: their body temperature is usually the same as its surroundings.
Some sharks, pelagic sharks, are capable of maintaining their temperature as much as 10C above the surrounding water by using a countercurrent exchange system called a rete mirabile.
Rete mirabile is a system of veins and arteries where cold/oxygenated blood from the gills flows past the warmer deoxygenated blood from the muscles. The cold blood is warmed by the deoxygenated blood before it enters the muscle. This allows the the muscles to work faster and stronger since there is no need to warm up the muscles. Sharks that use this system to increase their body temperature have three sets of retia: one in the swimming muscles, another in the anterior viscera, and a third surrounding the brain.
rm = rete mirabile
Sharks such as makos and great whites are capable of maintaining their temperature greater than that of the water, by using rete mirabile, making them supreme predators in the water. Because their body temperature can be up to 10C more than the water they are able to move much faster than a fish that is the same temperature as the surrounding water.
"Great White Shark." Wikipedia, The Free Encyclopedia. 5 April 2008, at 23:51 UTC. Wikimedia Foundation, Inc. 22 April 2008. http://en.wikipedia.org/wiki/Great_white_shark
Works Cited:
http://www.elasmo-research.org/education/topics/p_warm_body_1.htm