LiveScience's Image of the Day

How Sharks Stay Warm

Tuesday November 1, 2005

More Images...

North Pacific salmon sharks spend their entire lives swimming. If they didn't, they'd sink. Now new research shows that swimming actually warms up these cold-blooded creatures, allowing them to survive chilly 47 degree Fahrenheit waters.

As the sharks are swimming, the red muscle used to propel them through the water generates heat. As this muscle heats up, the warmth spreads from their body's core to the surrounding white muscle and warms the rest of the body. To keep the rest of their body warm, these sharks keep their red muscle temperature between 68 and 86 degrees Fahrenheit.

Scientist had believed in this mechanism for years, but didn't have evidence until Robert Shadwick of the Scripps Institution of Oceanography caught several sharks in the Gulf of Alaska and measured temperatures throughout their bodies and tested the mechanical power of red muscle.

Shadwick and his colleagues showed that the red muscle is much more efficient at warmer temperatures. At 50 degrees Fahrenheit, red muscle produces only 25 to 50 percent of the power it produces at 79 degrees. The researchers concluded that if red muscle temperatures fall below 68 degrees Fahrenheit for an extended period, the shark's muscle function could be permanently impaired.

Salmon sharks are members of the lamnid group of sharks, which also include the mako and great whites. Sharks in this group share many physiological and anatomical characteristics with bony tuna and probably shared a common ancestor more than 400 million years ago.

These results are published in the Oct. 27 issue of the journal Nature.

--Bjorn Carey

Amazing Images: Science & Nature Photos from Our Readers

Credit: Zina Deretsky, National Science Foundation

Advertisement

From the Blogs

LiveScience Blogs
  1. The Bug Hunt Is On. Target: Marine Aliens
  2. HARPS Discovery - HD 40307 And Its Three Super-Earths
  3. Can This British Columbia Lake Tell Us Something About Life On Other Planets?
  4. Power Equals Positive Action But Only When Acquired Legitimately
  5. X Chromosome Gets Some Respect As An Evolutionary Tool
  6. Estrogen Therapy May Limit Strokes In Women - But The Timing Has To Be Right
  7. Reminder: Garth Sundem's Foolproof Equations On The Science Channel Tonight At 6PM
  1. 6.15.2008 | Tariq Malik
    Father?s Day on Earth, in Space
    t’s Father’s Day on Earth, and just in time for the seven-astronaut crew of NASA’s shuttle Discovery, which landed yesterday in... ...
  2. 6.14.2008 | Robert Roy Britt
    Cutting the Technotether That Ruins Your Life
    he deluge of office and personal email and IM and texting, along with web surfing, putzing with iTunes and so on has workers increasingly distracted... ...

Related Items from the LiveScience Store

  1. Go to Store
  2. Go to Store

More Stores to Explore