How do Insects Breathe?
The insects breathe through the trachea. This takes the oxygen to the animal and expels the carbon dioxide from its metabolism.
Insects, like people, require oxygen to live and release carbon dioxide, but nevertheless, it can not be said that insects breathe as humans understand them.
Insects lack lungs or gills to receive oxygen from air or water. They also do not transport oxygen through their circulatory systems. You may also want to know more about tracheal breathing: characteristics and examples of animals.
Breathing in insects: the tracheal system
The insects absorb the air through small holes that cover the lower part of their bodies called spiracles, or respiratory pores. These open when the insect expands the muscles of your abdomen and close when the insect contracts its abdominal muscles.
When the air enters the spiracles, it moves through the tracheal system, formed by an extensive network of very thin tubes that run throughout the body of the insect.
These tracheas, when branching, are getting thinner, getting into all the tissues, reaching the cells. It is similar to what happens in humans with respect to blood capillaries.
Insects breathe by diffusion
The exchange of gases, or what we understand as respiration, is mainly done through diffusion through the cell walls, bringing oxygen directly to the different tissues of the body.
The air that reaches the tracheas, through diffusion, is distributed throughout the tissues reaching the cells, supplying the necessary oxygen while collecting the excess carbon dioxide, which is expelled through the spiracles.
This explains the movement of gases. In addition, to some extent, insects are able to control their breathing. The insect opens and closes the spiracles using muscle contractions.
An insect that lives in a dry and desert environment will keep the valves of the spiracles closed to prevent the loss of moisture.
The insects can also pump the muscles through their bodies to force the air through the tracheal tubes, thus accelerating the supply of oxygen.
In heat or under stress, insects can even release the air by alternately opening different spiracles and using the muscles to expand or contract their bodies.
The respiratory system of an insect is very efficient for small organisms. As body size increases, efficiency decreases. When the diameter of the body exceeds 3 centimeters, the respiratory needs can not be met.
Therefore, it is the insect’s respiratory system that restricts its body size. It should be borne in mind that no transport system, such as blood, is involved in the movement of oxygen or carbon dioxide around the body.
How do aquatic insects breathe?
While oxygen is abundant in the air (O2 levels in the air are 200,000 parts per million), it is considerably less accessible in water (reaching only 15 ppm). Despite this respiratory challenge, many insects live in the water during some stages of their life cycle.
Most insects can survive underwater for long periods by closing their spiracles and slowing their metabolism, but aquatic insects have made some special adaptations to survive underwater.
Aquatic insects, to increase their absorption of oxygen in water while submerged, employ structures that effectively increase the surface area available for gas exchange.
Many insects that inhabit the water have tracheal gills, tiny tracheal structures that allow them to take more oxygen from the water than they could otherwise, in a similar way as fish do.
These gills are often found in the abdomen, but in some insects they are found in strange and unexpected places. Some plecópteros, for example, have anal gills that seem a group of filaments that extend from their back ends. Or, like dragonfly larvae, which have gills inside their rectums.
Some aquatic invertebrates use respiratory pigments to extract oxygen from water. The larvae of non-biting mosquitoes (of the chironomid family), among a few groups of insects, possess hemoglobins, as do the vertebrates.
The chironomid larvae, due to hemoglobin, have a bright red color, from which the name comes from blood worms or red worms.
These blood worms can develop even in water with exceptionally low oxygen levels. They ripple their bodies in the muddy bottom of lakes and ponds saturating their hemoglobins with oxygen.
When they stop moving, hemoglobins release oxygen, allowing them to breathe even in the most polluted aquatic environments.
However, some insects that inhabit aquatic environments, get their oxygen from the air, using an open trachea system similar to terrestrial insects. Some of these aquatic insects, such as rat tailworms, maintain a connection to the air surface through a structure similar to that of a diving tube.
Some species of mosquito larvae take advantage of the oxygen supplies that some aquatic plants store underwater called vacuoles.
Oxygen is a waste product of your respiratory cycle, but it helps you to float. Mosquito larvae use their respiratory tubes to perforate the vacuoles and breathe in oxygen.
Some beetles and aquatic insects are able to dive by carrying a temporary bubble of air with them, much like a diver carrying an air tank.
Others, such as the elmidae beetle, of the coleoptera class, maintain a permanent film of air around the bodies.
These aquatic insects are protected by a network of tiny mesh bristles (hairs) that repel water, providing a constant airspace from which to extract oxygen. This structure, called plastron, allows them to be permanently submerged.