Where and how insects breathe

Insects do not have lungs like mammals, nor gills like fish, but rather have a respiratory system made up of tracheae , with which they carry oxygen directly to the tissues. The tracheal respiration is based on a system formed by a complex network of thin tubes, called tracheae, and running through the whole organism of the insect.

The spiracles are a kind of pores that protrude to the outside of the thicker tracheae. These spiracles are located at the abdominal and thorax level and are protected by small hairs that prevent small particles or microorganisms from entering the tracheae. At the entrance of the spiracles there are special rings that open and close allowing air to enter. The most superficial tracheae are those that thicken, while the innermost tracheae become increasingly thin until they form trachealas. Depending on the species of insect, you can use some spiracles to inhale and others to exhale, or both for both.

Other types of animal respiration

For example, cutaneous respiration , where animals use their tegument to carry out the process of gas exchange. For this type of breathing to occur, the skin must be thin and moist. Have breathing skin annelids like earthworms and leeches, amphibians like frogs, toads and salamanders and echinoderms such as sea urchins and sea stars.

Another type is gill respiration , in which the process occurs in the gills, which can be external or internal. They consist of membranes with which marine animals consume oxygen from the water, although previously the water enters through the mouth and is absorbed by the blood vessels located in the gills. Gill respiration is found in most fish.

The last type of respiration is pulmonary respiration , in which the oxygen captured by the nose passes through the pharynx, larynx, trachea, bronchi and bronchioles, until it reaches the alveolar sacs, where oxygen is already diffused into the capillaries of around.

As we have already indicated, insects have tracheal respiration , which consists of a system of tubes directly connected to the cells of the body through which the captured oxygen reaches them. A characteristic of insects is that they have an open circulatory system in which the blood circulates very slowly, providing a large amount of oxygen to the body. The process of respiration of insects explained in a simple way is this:

1. Oxygen enters the insect’s body through the spiracles.
2. This oxygen that has penetrated the body travels through this system of tubes until it reaches each tissue of the body, where oxygen is exchanged towards the cells and carbon dioxide towards the tubes at the same time.
3. The exchange takes place by diffusion between compartments with different gas concentrations until they are leveled.
4. From this oxygen the cells carry out their metabolism and generate carbon dioxide, which passes through diffusion into the tracheas and is eliminated from the body.

Oxygen is an abundant gas in air (its levels reach 200,000 parts per million), but not in water (its levels reach 15 ppm). This represents a great inconvenience for respiration, however many insects inhabit water during some stages of their life. Most insects can survive long periods underwater by closing their spiracles and slowing down their metabolism, but some have adaptations.

Many aquatic insects have tracheal gills , which are small structures in the trachea that allow them to extract more oxygen from the water than they normally obtain. Normally, these gills are found on the abdomen, with a few exceptions, such as some plecoptera (anal gills) or dragonfly larvae (rectal gills).

Some aquatic insects use respiratory pigments to extract oxygen , such as non-biting mosquito larvae (chironomids), which possess hemoglobin, such as the ones you can see in the image below.

Others maintain a connection to the outside air through a structure that resembles a diving tube. Some mosquito larvae take advantage of the oxygen that some aquatic plants store in their vacuoles. There are even some beetles that carry a temporary air bubble with them