The Tracheal breathing Is the most commonly used respiration by insects, centipedes, ticks, parasites and spiders.
In these insects, the respiratory pigments are absent from the blood, because the tracheal system is responsible for distributing O2 (air) directly to the cells of the body.
Tracheal breathing allows the gas exchange process to occur. In this way, a series of tubes or tracheas are located strategically in the body of the insects. Each one of these tracheas counts on an opening towards the outside that allows the entrance and exit of gases.
As in vertebrate animals, the process of ejecting gases from the body of insects depends on the contracting muscular movement that presses all the internal organs of the body, forcing the CO2 out of the body.
This type of respiration takes place in most insects, including those that inhabit aquatic environments.
This type of insects has bodies specially prepared to be able to breathe while they are submerged below the water level (Society, 2017).
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Parts of the tracheal breathing system
Windpipe
The trachea is a widely branched system with small ducts through which air passes. This system is located throughout the body of insects.
The presence of ducts in it is possible thanks to the existence of body walls aligned internally by a membrane known as ectoderm.
An insect has several tracheas or ducts that open to the outside of its body, allowing the gas exchange process to take place directly in all Cells Of the body of the insect.
The area where there is a greater concentration of branches is usually the insect's belly, which has numerous ducts that progressively give air into the body.
The complete trachea system of an insect is generally composed of three main channels located parallel and longitudinal in relation to its body. Other small ducts pass through the main trachea, forming a network of tubes that covers the whole body of the insect.
Each of the tubes that has an outlet to the outside, ends in a cell called tracheal cell.
In this cell, the tracheas align with a layer of protein known as trachein. In this way, the outer end of each trachea is filled by tracheolar fluid (Site, 2017).
Spiracles
The tracheal system opens outwards through cleft openings called stigmas or spiracles. In cockroaches, there are two pairs of spiracles located in the thoracic region and eight pairs of spiracles located in the first segment of the abdominal region (Stidworthy, 1989).
Each spiracle is surrounded by a sclerite called peritrema and has bristles that act as filters, preventing dust and other particles from entering the interior of the tracheas.
Spiracles are also protected by valves attached to the occluder and dilator muscles that regulate the opening of each tube.
Gaseous exchange
In resting state, the tracheas are filled by a capillary fluid thanks to the low osmotic pressure in the cells of the body tissue. In this way, the oxygen entering the ducts dissolves in the tracheolar fluid and CO2 is released into the air.
The tracheolar fluid is absorbed by the tissue when the volume of lactate increases once the insect enters the flight phase. In this way, CO2 is temporarily stored as bicarbonate, sending signals to the spiracles to open.
However, the greater amount of CO2 is released through a membrane known as cuticle (biology-pages, 2015).
Ventilation movement
Ventilation of the tracheal system is performed when the muscle walls of the insect's body contract.
Expiration of body gas occurs when the abdominal-abdominal muscles contract. Conversely, air inspiration happens when the body takes its regular shape.
Insects and some other invertebrates perform gas exchange by removing CO2 through their tissues and taking air through the tubes called tracheas.
In crickets and grasshoppers, the first and third segments of your thorax have a blowhole on each side. Similarly, eight other pairs of spiracles are located linearly on each side of the abdomen (Yadav, Physiology of Insects, 2003).
The smaller or less active insects perform the gaseous exchange process by diffusion. However, insects that breathe through diffusion can suffer in drier climates, as water vapor does not abound in the environment and can not diffuse into the body of the same.
Fruit flies avoid the risk of dying in dry environments by controlling the size of the opening of your spiracles, so that they adapt to the oxygen requirement of the muscles during the flight stage.
When the oxygen demand is lower, the fruit fly partially closes its spiracles in order to retain more water in the body.
The most active insects such as crickets or grasshoppers, must constantly ventilate their tracheal system. In this way, they must contract the muscles of the abdomen and press the internal organs to force the air out of the tracheas.
Grasshoppers have large air sacs attached to certain sections of the larger trachea, in order to increase the effectiveness of the gas exchange process (Spider, 2003).
Aquatic insects: example of tracheal breathing
Aquatic insects use tracheal respiration to carry out the gas exchange process.
Some, like mosquito larvae, take in the air by exposing a small respiratory tube outside the water level, which is connected to their tracheal system.
Some insects that may be immersed in water for prolonged periods of time carry with them air bubbles from which they take the O2 they need to survive.
On the other hand, some other insects have spiracles located in the upper part of their back. In this way, they pierce the leaves that are suspended in the water and adhere to them to be able to breathe (Yadav, 2003).
References
- Biology-pages. (January 24, 2015). Retrieved from"Tracheal Breathing: Biology-pages.info".
- Site, T. O. (2017). How Living Organisms Breathe: Index . Retrieved from THE BREATHING SYSTEM OF INSECTS: saburchill.com.
- Society, T.A. (2017). Amateur Entologists' Society . Retrieved from Insect respiration: amentsoc.org.
- Spider, W. (2003). Insects and Spiders of the World, Volume 10. New York: Marshall Cavendish.
- Stidworthy, J. (1989). Shooting Star Press.
- Yadav, M. (2003). Biology Of Insects. New Delhi: DPH.
- Yadav, M. (2003). Physiology of Insects. New Delhi: DPH.