Wouldn’t it be nice to be able to hold your breath for five minutes? This is not a talent that would be of any practical use for a human, but it would be a really cool ability nonetheless. Studies have shown that several insects are capable of holding oxygen for several minutes without breathing. Butterfly pupae and beetles can avoid breathing for a few hours at a time. Roaches can only hold their breath for five to seven minutes. But why are roaches endowed with this particular ability?
A roach possesses internal air-filled tubes called trachea, which deliver oxygen directly to its cells. Oxygen enters the trachea of roaches through valves that are located on their bodies, called “spiracles”. For some reason, roaches will sometimes close their spiracles in order to cease respiration. Researchers are not exactly sure what function this serves, or why these valves are designed to open and close. Some researchers believe that the valves close to prevent further oxygen intake because too much oxygen can be toxic. The spiracles may close so that building up and expelling carbon dioxide becomes easier. And yet another reason involves water. Having spiracles that open and close would help roaches regulate their water loss. Having a tracheal system that delivers oxygen to cells will result in water vapor being expelled from cells. Therefore, when roaches don’t need oxygen they can keep their spiracles closed in order to prevent water from being expelled by their cells.
In order to find out why roaches have spiracles, entomologists conducted a study that had roaches inhabiting two different environments; one dry environment and one moist environment. It turns out that roaches do use their spiracles to prevent water loss, as roaches in dry conditions only opened their spiracles for short amounts of time in order to prevent water loss. In moist and humid conditions the roaches were able to stay hydrated, and, therefore, they could keep their spiracles open. A roache’s ability to directly control its own hydration levels makes it well suited for a variety of different environments.
Do you think that roaches developed spiracles as a result of evolving near regions that were plentiful in water?