Do whales get the bends?

A while back I was playing a video game called ABZÛ. This game is beautiful and incredibly well done. In this game you are a diver exploring different marine biomes. You get to see all kinds of different marine life as you travel through the zones of the ocean on your journey. At one point in the game as you are diving down into the depths, you encounter a pod of whales. It's a really neat scene and it helps convey the sheer size of these amazing creatures. You and the whales continue to dive down into the darkness till you reach the ocean floor. As the whales and your character are descending to depths, I got to thinking... "Why don't whales get the bends?"

*This one might be a little long, so for the super short condensed version, feel free to skip to the summary at the end. For more information on the bends and the specifics of how whales avoid this, read on!

"Excuse me Mr. Whale, how do you avoid the bends?" Screenshot from ABZÛ.

'The Bends', or Decompression sickness, is a phenomenon that occur when divers dive down to significant depth and then resurface too quickly. (It can also be caused due to extreme altitude gain and loss as well.) As you dive down the pressure on your body increases. As pressure increases it affects certain gasses in your body different. Nitrogen in particular gets compressed and absorbed into the tissues in your body. As your surface and the pressure decreases the Nitrogen starts to form bubbles and it wants to escape from the tissues in your body. However, it can take up to 12 hours for the Nitrogen to start escaping from your tissues. If you surface too quickly you could be in for a miserable time. (eMedicine Health)

Symptoms may be mild and primarily affect the musculoskeletal system. These would include headache, feeling ill, or having pain in the joints and muscles ranging from mild to severe. Depending on how long you were at depth, the depth to which you dove, and how quickly you surfaced, decompression sickness can also be severe and affect vital parts of your body like your brain and spinal cord. Symptoms of nerve damage would include tingling, numbness, paralysis (sometimes permanent paralysis), confusion, headache, double vision, and pain. Needless to say, having decompression sickness is not fun. (Merk Manual)

So why don't whales get decompression sickness? Sperm whales regularly dive to depths of 1,500 to 3,000 feet, with the deepest dives being recorded at 6,000 and 7,000 feet (Scientific American & National Geographic). Although Curvier's Beaked Whale just set a new record by diving to a depth of almost 10,000 feet (National Geographic)! Sperm Whales typically hold their breath for up to an hour at a time, but have been recorded to hold their breath for up to two hours. The Curvier's beaked whales that were recorded at diving to depths of 9,000+ feet held their breath for a whopping 138 minutes. That's 2 hours and 18 minutes! @.@

To put this in perspective, here are some numbers describing what a Whale experiences at regular hunting depth of 3,000 feet below the surface: "Now she [the whale] is about 1000 meters (3280 feet or 3/5 of a mile) below the surface. Eleven football field lengths of water is above us. The pressure is 1421 pounds per square inch (almost 100 atmospheres). 200,000 pounds (100 tons) of water press on every square foot of the whale. ... At this depth the air in the whale's body is one percent of its original volume, and it is 100 times more dense (FT Exploring)."

As far as science has been able to determine, whales are able to survive at these depths and make these kinds of amazing dives dozens of times per day because of some very special physical adaptations. Whales spend around 10 to 15 minutes at the surface clearing their lungs and filling up on oxygen. Once they are good to go they start diving. As they dive and the pressure increases the whale's rib cages are built to collapse to accommodate for the crushing pressure at such depths. Any air cavities in a whale's body are squeezed shut. Air cavities like the middle ear and airways are lined with very vascular tissues which are believed to swell up so there is no open space that would collapse. A whale's lungs also collapse, which is very important in regards to avoiding the bends.

When the whale's lungs collapse, all the air is forced out of the lungs and into the blood stream and the muscles. No exchange of gasses is taking place, which means that Nitrogen cannot be absorbed into the body the same way it does in the bodies of humans under pressure. Whales have almost 3.5x more blood per kilogram of body mass than humans do. Further, their concentration of hemoglobin (which is a protein in the blood that transports oxygen) is about 2x what we humans have. In addition, they have 10x more myoglobin in their muscles than we do! (Myoglobin is a protein in the muscles that stores oxygen). This means that as whales descend to the depths all the oxygen in their lungs is moved into their blood and their muscles for storage and use. (Scientific American).

To Summarize: Whales don't get the bends because they are specially adapted to allow the pressure to compress certain parts of their body, including their ribs and lungs. This squeezes all the oxygen into their blood and muscles, which contain significantly more oxygen storage proteins than humans. This also prevents Nitrogen from being exchanged in the lungs during the breathing process, which in turn keeps it from building up in the blood stream and tissues. This prevents the Nitrogen from causing decompression sickness (or the bends) as it escaped the tissue later when the whale returned to the surface. No Nitrogen in your tissue = no decompression sickness or nitrogen narcosis.

There you have it. Whales are the unsung bad-asses of the ocean, regularly withstanding 1421 pounds of pressure per square in on their bodies just to dive down and grab a snack, which they can do... Because Science!

Cheers!

Fliff



SOURCES:
eMedicine Health
Merk Manual
Scientific American
National Geographic
FT Exploring