Think you're under pressure? Try diving 200 meters below the ocean. That's where fin whales (Balaenoptera physalus) spend their time feeding. That kind of pressure would rupture our blood vessels, but whales do just fine. To figure out why, researchers compared whale arteries to those of pigs, chosen for their relation to the whale's land-loving ancestors. Then they ran saline or water over and through the vessels. The arteries, which draw blood away from the heart, stiffened in the fin whale, while the pig arteries stretched out and collapsed under far less stress, the team reports online this week in The Journal of Experimental Biology. The finding suggests that the whales benefit from naturally occurring collagen around their arteries. Firming up to withstand the depths, this connective tissue may be what keeps whales from feeling the squeeze.
*Correction, 1 p.m., 28 June: The researchers did not test the aortic arch; rather, the arteries stiffened in the fin whale. This has been corrected.