Roaches are hardy insects. According to Dr. Coby Schal of North Carolina State University, large species of roaches can live up to a month without their heads while German roaches can live for up to one week after decapitation. Roaches can also live up to a month without food. However, roaches still need to breathe, and their efficient respiratory systems ensure that necessary oxygen reaches the roach’s tissue directly.
Understanding how roaches breathe requires some knowledge of their respiratory anatomy. Roaches have 10 pairs of stigmata, or respiratory openings, on their bodies. Eight pairs are located on the insect's abdomen while the other two pairs are located on the thorax region near the front of the body. These stigmata lead to spiracles, external openings that bring oxygen into the insect's trachea. Shooting off from the tracheal tubes are small branches known as tracheoles, which bring the oxygen to the roach's tissue. All of these respiratory components work thanks to the tergo-sternal muscles, a group of muscles connected to the roach's body between its sternal and tergal plates.
To breathe in oxygen, the roach's tergo-sternal muscles relax, causing the pressure within the insect's body cavity to decrease. This decrease in pressure prompts the spiracles located in the abdominal region to close while the thoracic spiracles open. The oxygen comes in through the thoracic spiracles, moves through the tracheal trunks to the tracheoles. From there, tracheolar fluid takes the oxygen into the tissue.
As a result of the tissue's use of oxygen, carbon dioxide is produced and needs to be eliminated from the roach's body. To do this, the tergo-sternal muscles must tighten and increase pressure inside the roach's body. The pressure causes those thoracic spiracles to close while the abdominal ones open to release the carbon dioxide.
Complex Breathing Patterns
The basic inspiration and expiration process of the roach sounds simplistic, but the roach has more complex ways of controlling its respiration. Roaches don't breathe non-stop. In humans, for example, the cycle of bringing in oxygen and expelling carbon dioxide is continuous; it does not stop even when we sleep. In roaches, however, all of the spiracles can close down causing discontinuous ventilation. Additionally, a 2009 study published in the Journal of Experimental Biology found roaches kept their spiracles closed for longer periods when their environment was drier. Lead scientist Dr. Craig White believes this increased period of closure allows the roach to keep more of its own moisture locked in; roaches can dehydrate in a week without water.
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