This method of gas exchange is extremely limited. This is because the insect’s method of gas exchange cannot be ‘accelerated’. A mammal’s gas exchange can be regulated by lungs which can be accelerated as too speed up gas exchange. This cannot happen in an insect, it is also inefficient as the larger the insect is the more oxygen it needs however it can’t use active transport to move oxygen into the trachea. This oxygen is diffused which is a slow process so therefore insects in the current climate just cannot grow to large sizes.
However insects from 360 million years ago were a very large size, with Palaeozoic Era Dragonflies reaching up to 65 centimetres. This is because the oxygen level was so much greater. As the insect size is limited by oxygen levels, if the oxygen concentration in the atmosphere is greater than the insects size would get larger as its robust gas exchange system can support a larger organism with more cells.
This research can be used for when insects are crystallised in rocks such as amber, by comparing their tracheal size they can deduce how much oxygen there was in the atmosphere which means they can roughly pinpoint when the creature was alive. They can also find the oxygen concentration in the atmosphere from insects at known points in time to confirm original theories about oxygen levels. The researchers hope to study the dragonflies’ behaviour at different oxygen levels to further understand prehistoric giant insects and their place in the food chain.
I chose to write about this article as I find it very interesting when I was shown it but also that in our a-level syllabus for biology we learn about insect gas exchange which is featured heavily in this article