Prehistoric gigantic flying insects, including a dragonfly with a wingspan of 75cm, died millions of years ago due to a lack of oxygen in water which had made them giant in the first place, according to a new study.
They believe that larvae 300million years ago took advantage of the higher oxygen levels available, using it to help fuel their growth to the size shown in fossilised remains found by palaeontologists today.
When the climate later changed and the oxygen level dropped, the larger species” larvae could not take in enough of the gas to survive and the species went extinct, leaving only their smaller relatives alive.
“In prehistoric times, higher levels of oxygen may have favoured the evolution of giant insects largely through their effects on larvae, and it is perhaps no accident that many extinct giants had aquatic juvenile stages,” the Daily Mail quoted Dr David Bilton, of Plymouth University”s School of Marine Science and Engineering, who carried out the research, as saying.
The research, which looked at the stonefly (Dinocras cephalotes), said aquatic larvae, such as those of dragonflies, stoneflies and mayflies, extract their oxygen directly from the water, where far less is available than in air.
The larvae were also less efficient at extracting oxygen from the water than their air-breathing elders.
This, the scientists suggest, would make them more sensitive to changes in available oxygen and therefore the gas”s role in shaping insect body size may be particularly important in aquatic larvae, setting an upper size limit.
The study has been published in the Public Library of Science.