When humans finally give up on this world and return to the sea, we’re going to have to learn to dive deep. To do that, we may need to borrow a few genes from the humble copepod, and pack ourselves with fat.
The copepod is a tiny, shrimp-like creature. The trouble with being a tiny, shrimp-like creature in the ocean is the entire ecosystem is based on eating you. You’re munched on by the largest animals alive and the tiniest hatchling struggling out of their eggs alike, and all you can eat are algae. Copepods cope with stress by taking a winter vacation. After eating gorging themselves all summer, they dive down to 3500 meters and hibernate all winter.
This was a physics mystery for quite some time, because after gorging themselves, the copepods were nearly half fat, and fat is less dense than water, so it floats. Copepods can swim fairly well, but if they had to swim to maintain depth, they’d burn through their fat and be unable to hibernate. So how did these creatures overcome physics? By building strategic fat.
Scientists found that the deeper they fished for copepods, the fatter copepods they found. They also found that the fattest copepods had large amounts of compounds called polyunsaturated wax esters. These compounds are collapsible fats. When the temperature is warm and the pressure is off, they’re a liquid that floats. As the temperature drops, the fats get solid. As the copepod swims down, the extra water pressure makes the fat even denser. Once it gets dense enough, it turns from a balloon, keeping the copepod up, to a weight, pulling it down. Once it gets to a pressure and temperature that give the copepod a neutral buoyancy, it can hang out there all season.
So when we trade in our legs for fins – or when we next take a look at mermaids – perhaps these creatures can show us a way to attain the right depth using nothing but a little extra weight on the hips.