The respiratory system of insects is interesting facts. Breathing of insects. Insects that have gills
In insects, it is the most accurate reflection of their lifestyle. Since these creatures are always above the ground, they breathe exclusively thanks to their tracheas, which they have much more developed than those of other inhabitants of our planet. In fairness, it is worth highlighting that there are some superclasses of insects that live in the aquatic environment, or are often there. In this case, the respiratory system of insects is represented by gills. However, this is extremely rare species of this class, therefore we will also examine them very briefly. Well, let's move on to a more detailed study of this section of biology.
General information
So, the respiratory system in insects appears to us in the form of tracheas. Numerous branches emanate from them, which spread throughout all the vital organs and systems of the body. The entire body, with the exception of the head (that is, the thoracic region and abdomen) is covered with exit openings - spiracles. They form the tracheal system, thanks to which most insects can breathe through the surface of their body.
It is worth noting that these spiracles are reliably protected from irritants external environment special valves. They quickly respond to the supply of air thanks to their well-developed muscles. It is also important to know that spiracles are found on the sides of each body segment. The size of their holes is adjustable, due to which the tracheal lumen changes.
Ventilation process
To understand thoroughly how insects breathe, it is important to first understand that each tracheal system, which is located in the body, is always ventilated. The necessary air exchange occurs due to the fact that the valves, which are located along the body, roughly speaking, open and close according to a certain schedule, that is, in a coordinated manner. For example, consider how a similar process occurs in locusts. During the entry of air, the anterior 4 spiracles open (including two thoracic and two anterior abdominal ones). At this time, all the others (6 rear ones) are in the closed position. After the air has entered the body, all the spiracles close, and then the opening occurs in the following sequence: the 6 rear ones open, and the 4 front ones remain closed.
Basic breathing movements
Many years ago, scientists, looking at how insects breathe, noticed that their bodies compress and unclench in a certain way. This process turned out to be synchronous with the process of oxygen entering the body, which is why it was concluded that many representatives of arthropods breathe precisely thanks to standard mechanical actions. Thus, the respiratory system in insects can function due to contractions of individual sections of the abdomen. This type of “breathing” is characteristic primarily of all terrestrial creatures. Those individuals who live partially or completely in water are also characterized by a reduction in some of the thoracic regions. It is also important to remember that muscle contraction occurs during exhalation. When air enters the body, all the abdominal and thoracic segments of the insect, on the contrary, expand and completely relax.
The structure of the trachea
It is the trachea, as mentioned above, that represents the respiratory system of insects. For children, such a concept may be too complicated, so if you are explaining this biological process to your child, then first tell him what this very respiratory organ looks like. In almost all insects, each trachea is a separately existing trunk. It comes from exactly the valve through which the spiracle passes. Branches emanate from the tracheal tube, which are presented in the form of a spiral. Each such branch is formed from a very dense cuticle, which is always securely fixed in place. Thanks to this, the branches do not fall off or become tangled, therefore, gaps are always preserved in the insect’s body, through which oxygen and carbon dioxide can circulate normally, and without which the life of this class is unrealistic.
How are flying insects different?
The respiratory system of insects that can fly looks a little different. In this case, their bodies are equipped with so-called air sacs. They are formed due to the expansion of the tracheal tubes. Moreover, these expansions are much greater than the original width of the respiratory organ. One more characteristic feature such bags - they do not have spiral seals, so they behave much more mobile inside the insect’s body. The expansion and contraction of air sacs in flying insects occurs passively. During inhalation, the body increases, and during exhalation, it decreases accordingly. During this process, only the muscles that control everything are used. It is also important to note that the respiratory system of flying insects is designed so that they can capture more oxygen.
Insects that have gills
Arthropods that live in water bodies, like fish, have gills and gill openings. In this case, the respiratory process is still carried out thanks to the trachea, however this system closed in the body. Thus, oxygen from the water enters the body not through the spiracles, but through the gill slits, after which it enters the tubes and spirals. If the insect is designed in such a way that, with the process of growing up, it gets out of aquatic environment, begins to live on the ground or in the air, then the gills become a rudiment that disappears. The tracheal system begins to develop more actively, the tubes and spirals become stronger, and the breathing process no longer has anything to do with the gills.
Conclusion
We briefly looked at what the respiratory system is like in insects, how it is characteristic, and what varieties of it can be found in nature. If you dig deeper, you will find out that the respiratory systems of arthropods of various categories are very different from each other, and most often their features depend on the habitat of certain species.
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Structure of the tracheal system. Insects breathe through a system of tracheas distributed throughout the body, less often through the surface of the skin. The tracheae are represented by hollow tubes lined with chitin in the form of spiral thickenings that prevent the trachea from collapsing during movement and bending of the body. The tracheae branch into tiny capillaries - tracheoles with a diameter of less than 1 micron, which deliver air oxygen directly to the tissues and cells of the body.
Breath. The entry of air into the tracheal system most often occurs actively, with the help of respiratory movements. In this case, certain spiracles open or close, inhaling or exhaling. The rhythm of respiratory movements depends on the type of insect, its condition and external conditions. Thus, a honey bee at rest makes about 40 respiratory movements per minute, and when moving - up to 120; in some locusts, an increase in their number from 6 to 26 or more occurs with an increase in environmental temperature from 0 °C to 27 °C and above.
In many species of insects, air is inhaled through the pectoral spiracles and exhaled through the abdominal spiracles. The rhythm of the spiracles is associated with the respiratory movements of the abdomen; with an increase and decrease in air pressure caused by these movements, some spiracles open outward, others open into the insect's body. However, under the influence of large doses of carbon dioxide, various poisons, and sometimes for no apparent reason, air circulation can change, that is, it begins to enter through the abdominal spiracles and exit through the thoracic ones. In addition, with an increase in carbon dioxide content and a lack of oxygen in the environment, the spiracles remain open for a longer time, and therefore fumigation of the premises against pests will be more effective.
Respiration is an oxidative process that occurs through the consumption of oxygen and the release of carbon dioxide. The oxidation process occurs with the participation of oxidative enzymes - oxidases and is accompanied by the gradual breakdown of molecules of consumable compounds - carbohydrates, fats, proteins - and the release of energy. The breakdown of these compounds ultimately ends with the formation of carbon dioxide and water, and for proteins, also the appearance of breakdown products that are bound into compounds that are safer for the body, such as urea and its salts.
Thus, breathing is accompanied by gas exchange. The gas exchange process is characterized by the respiratory coefficient (RC), which represents the ratio of released carbon dioxide to the total amount of absorbed oxygen. Based on this indicator, one can judge which substances are used in at the moment as a source of energy. When oxidizing carbohydrates, DC = 1, when using less oxidized fat compounds, DC decreases to 0.7, and proteins - to 0.77-0.82. For example, when cockroaches are starving, the DC decreases to 0.65-0.85, which corresponds to the predominant consumption of previously stored fats.
Other forms of breathing. Respiration of aquatic insects occurs both due to atmospheric air and through the use of air dissolved in water. Thus, swimming beetles, living in water, breathe using atmospheric air stored under the elytra at the end of the abdomen, and from time to time rise to the surface to replenish its reserves. Beetles from the genus iris extract atmospheric air from the air vessels of aquatic plants.
When using air dissolved in water, insects breathe using gills. The gills are represented by external branched or lamellar formations located in the place of the missing spiracles. They are developed in the larvae of mayflies, dragonflies, caddisflies, and some dipterans. In the larvae of heteroptera dragonflies, the gills are rectal, that is, they are internal organs and are located in the rectum.
Body temperature. Insects are animals with variable body temperatures. It depends on the intensity of heat generation processes and its release. The sources of heat formation in insects are, on the one hand, metabolic processes in the body, accompanied by the release of thermal energy, and the radiant energy of the sun or the air heated by it, on the other.
According to I.D. Strelnikov, the body temperature of insects that are at rest and not exposed to sun irradiation is approximately equal to the temperature environment. Due to the fact that the temperature optimum for many species fluctuates around 20...35 °C, insects can regulate body temperature within certain limits by changing muscle activity (movement, flight) or moving to warmer or cooler areas, sometimes beyond posture change account. Known value evaporation of water from the surface of the skin and ventilation of the trachea, especially with the help of air sacs, can help regulate body temperature.
U insects Living in water, breathing occurs in two ways. It depends on the structure of their tracheal system.
Many aquatic organisms have a closed tracheal system in which the spiracles do not function. It is closed and there are no “exits” to the outside. Breath carried out with the help of gills - outgrowths of the body into which the trachea enters and branches abundantly. Thin tracheoles come so close to the surface of the gills that oxygen begins to diffuse through them. This allows some insects living in water (larvae and nymphs of caddisflies, stoneflies, mayflies, dragonflies) to carry out gas exchange. During their transition to terrestrial existence (transformation into adults), the gills are reduced, and the tracheal system turns from closed to open.
In other cases, the respiration of aquatic insects is carried out by atmospheric air. These insects have an open tracheal system. They take in air through their spiracles, floating to the surface, and then sink under the water until it is used up. In this regard, they have two structural features:
- firstly, developed air sacs in which large portions of air can be stored,
- secondly, the developed closure mechanism of the spiracles, which does not allow water to enter the tracheal system.
Other features are possible. For example, in the larva of a swimming beetle, the spiracles are located at the posterior end of the body. When she needs to “take a breath,” she swims to the surface, takes a vertical position “upside down” and exposes the part where the stigmata are located.
In the larva of a common mosquito, a respiratory tube extends upward and backward from the 8th and 9th segments of the abdomen connected together, at the end of which the main tracheal trunks open. When the tube is placed above the water, the insect receives air through the gaps in the trunks. An almost identical, but more pronounced tube is found in the larvae of Eristalis. This formation is expressed so strongly in them that for its presence and gray In the insect itself, such larvae are called “rats.” Depending on whether it is at greater or less depth, the rat’s tail can change its length. (photo)
The breathing of adult swimmers is interesting. They have developed elytra, bending downwards and inwards towards the body on the sides. As a result, when floating to the surface with the elytra folded, the beetle captures an air bubble, which enters the sub-elite space. This is where the spiracles open. This is how the swimmer renews its oxygen reserves. The swimmer of the genus Dyliscus can stay under water for 8 minutes between surfacings, Hyphidrus for about 14 minutes, and Hydroporus for up to half an hour. After the first frost, the beetles also remain viable under the ice. They find air bubbles underwater and swim over them so as to “take” them under the elytra.
In the water lover, air is stored between the hairs located on the ventral part of the body. They are not wetted, so a supply of air is formed between them. When the insect swims underwater, its ventral part appears silvery due to the air cushion.
In aquatic insects that breathe atmospheric air, the small reserves of oxygen that they capture from the surface should be consumed very quickly, but this does not happen. Why? The fact is that oxygen diffuses from water into air bubbles, and carbon dioxide partially escapes from them into the water. Thus, by taking air under water, the insect receives a supply of oxygen, which is replenished by itself for some time. The process is highly temperature dependent. For example, the Plea bug can live in boiled water for 5-6 hours at warm temperatures and 3 days at cold temperatures.
Insects do not have lungs. Their main respiratory system is the trachea. The tracheae of insects are communicating air tubes that open outward on the sides of the body with openings called spiracles. The finest branches of the trachea - tracheoles - penetrate the entire body, entwining organs and even penetrating inside some cells. In this way, oxygen is delivered with air directly to the place of its consumption in the cells of the body, and gas exchange is ensured without the participation of the circulatory system.
Many insects living in water (aquatic beetles and bedbugs, mosquito larvae and pupae, etc.) must rise to the surface from time to time to capture air, i.e. they also have air breathing. While the air supply in the tracheal system is being renewed, the larvae of mosquitoes, centipedes and some other insects are “suspended” from below to the surface film of water using non-wettable fatty hairs.
And aquatic beetles - water lovers (Hydrophilidae), diving beetles (Dytiscidae) and bugs, for example, smooth beetles (Notonectidae) - having breathed at the surface, take an additional supply of air with them under the water under the elytra.
In insect larvae living in water, in moist soil and in plant tissues, cutaneous respiration also plays an important role.
The larvae of mayflies, stoneflies, caddis flies and other insects, well adapted to life in water, do not have open spiracles. Oxygen penetrates inside them through the surface of all parts of the body where the integument is quite thin, especially through the surface of leaf-shaped outgrowths penetrated by a network of blindly ending tracheas. The larvae of bloodworm mosquitoes (Chironomus) also breathe through the skin, over the entire surface of the body.
