Larvae of the lake fly Chaoborus edulis in Lake Malawi complete daily dives exceeding 200 meters to evade predators. Their air sacs, reinforced with the elastic protein resilin, endure pressures equivalent to more than 400 meters of water depth.
Billions of these larvae migrate vertically each day. They descend into low-oxygen zones during daylight hours and ascend at night to feed, passing through schools of predatory fish.
University of British Columbia researchers Philip Matthews and Evan McKenzie tracked the movements with a lake-floor sonar system. Examination revealed two pairs of air sacs that function like submarine ballast tanks. The larvae adjust sac volume by altering pH levels in walls containing resilin.
Pressure-chamber tests showed the sacs remain intact at forces far beyond the larvae's normal range. This finding questions the long-held view that water pressure alone prevents insects from colonizing the open ocean.
The study received support from Natural Sciences and Engineering Research Council of Canada grants. The results appear in the journal Science.
