Open your mouth and throat, but hold your diaphragm and chest absolutely still. You aren’t quite holding your breath because some oxygen will still find its way into your lungs by the random diffusion of air molecules. However, it isn’t nearly enough to keep up with the demands of your body.
To survive without a diaphragm actively pumping air in and out of your lungs, you would need a much smaller body, or more than one throat. Ants have both. Depending on the species, ants have nine or 10 pairs of openings, called spiracles, along the side of their body.
Each spiracle is connected to an ever finer branching series of tubes called tracheae. This is similar to our lungs, except that insects don’t use blood to carry oxygen from the tracheae to the rest of the body. Instead, the tracheae spread throughout the body and each branch ends in a cul-de-sac with a moist end-wall that touches directly against the membrane of a cell.
This system only works in tiny animals. Once the body grows beyond a centimetre or two, the tracheae are simply too long for air to be able to diffuse along them fast enough.
Larger and more active insects have to supplement the passive breathing system by flexing their abdomens to pump air along the tracheae. But ant-size insects can manage just fine without this. In fact, a 2005 study at Berlin University found that many insects this size actually have to close their spiracles periodically so that they don’t get too much oxygen!
Asked by: Yofan Tamayo, London
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