Sperm whales can dive up to a thousand meters deep, gray whales migrate thousands of kilometers through the ocean – just two of the highest performances that large whales are capable of. The animals are driven by the powerful blow of their tail fins, which sends strong pressure waves through the whale's body every time. At the same time, the mammals have to hold their breath under water, which further increases the pressure in the body. Nevertheless, her blood vessels and her brain do not suffer any damage, as one would expect in humans. Robert Shadwick from the University of British Columbia and his team describe in "Science" why this does not happen.
The whales in the skull have a special network of blood vessels, the so -called Rete Mirabile: a network of the finest arteries that branches off from an artery and later unites an artery again. It was discovered in the 17th century and also occurs on the kidneys in other mammals. However, the importance of the large whales has long been unknown.
Shadwick and Co therefore developed a computer model with which the working group could simulate the pressure fluctuations in the whale body and its consequences for the vascular system. The model is based on the physiology of eleven different species from the bottlenose dolphin to the great whale.
According to the model, the Rete Mirabile plays a crucial role in the pressure equalization: it keeps the blood pressure in the brain constant without the whales having to weaken its tail strokes. The braid from blood vessels leads the pressure increase from the arteries that lead blood into the vessel through the network until the arteries pass into the veins that leave the brain. This distributes the pressure over a large area, which is why the RETE Mirabile looks like a protective helmet: it protects the whale brain from pressure fluctuations without changing blood flow in the rest of the body. According to the simulation, the vascular network "swallows" about 90 percent of the pressure rise that the tail strokes trigger: enough enough to dive deeply or swim powerfully without the stroke of the brain.
Seals or seals do not have this vascular network in their heads, which is related to their swimming style. They glide with lateral wave movements and thus ensure that new pressure pulses do not chase through the body again and again.
