Billions of lake fly larvae (Chaoborus edulis) in Lake Malawi, East Africa, are putting on a daily show that would make any submarine captain jealous. Every morning, they descend more than 200 meters into a low-oxygen dead zone to hide from predators, then rise at night to feed, running a gauntlet of hungry fish.

Researchers from the University of British Columbia, Drs. Philip Matthews and Evan McKenzie, deployed a sonar system on the lake floor to track this vertical migration. What they found inside the larvae was a surprisingly sophisticated buoyancy system: two pairs of air sacs that act like submarine ballast tanks. The sacs are lined with resilin, a super-elastic protein, and by tweaking the pH of the sac walls, the larvae can expand or contract the sacs to control their depth with precision.

To test the limits of these air sacs, the researchers placed the larvae in miniature pressure chambers. The sacs withstood pressures equivalent to depths of over 400 meters - far deeper than the larvae ever go. This toughness challenges a popular theory that pressure alone explains why insects are virtually absent from the open ocean. It seems these larvae have evolved a pressure-resistant design that could inspire new materials, like artificial muscles triggered by pH changes.

The study, funded by the Natural Sciences and Engineering Research Council of Canada, suggests that the ocean's lack of insects might be more about other factors - like the lack of a good lunch buffet or an overabundance of fish - than just the crushing depths.