Under pressure

摘要

Dip beneath the ocean and the pressure starts to rise, causing problems for anything adapted to living at the surface, like us. The most obvious difficulty is that rising pressure puts the squeeze on the lungs and any other air spaces in the body. To combat the effects, diving mammals that reach depths of over 1000 metres, such as elephant seals and sperm whales, allow their ribcage and lungs to collapse, squeezing the air out So they can go longer without breathing, they have higher levels of oxygen-binding haemoglobin in their blood, plus more of a similar molecule called myoglobin in their muscles.