About Lesson
RESPIRATORY SYSTEM OF INSECTS
Insects do not bear highly developed organs and they respire through an air tube called the tracheal system.
A) Tracheal system (trachea and tracheoles):
- In insects, the exchange of gases takes place through tubular structures, called trachea.
- The trachea is divided into very fine branches known as tracheoles. They supply oxygen to the body tissues.
- The tracheal system with functional spiracles is called the open tracheal system and with nonfunctional spiracles is called the closed tracheal system.
- Tracheoles form a network over the visceral organs including the alimentary canal as well as the gonads (ovaries, testis), penetrate the tissues of the organs become intracellular, and supply oxygen directly to the tissues.
Difference between trachea and tracheoles
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Trachea |
Tracheoles |
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a. These are large tubes running from spiracles. |
a. Fine tubes arising distally from the trachea. |
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b. Taenidia present |
b. Absent |
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c. The Intima layer is shed during molting. |
c. Intima layer retained or unchanged during molting |
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d. Never become intra-cellular |
d. Intracellular |
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e. The intima layer consists of a protein chitin matrix with resilin |
e. Protein-chitin matrix present resilin absent. |
B) Spiracles:
- They are the openings of the internal tubular trachea.
- Spiracles are absent in the prothorax and distributed in the meso, metathorax, and abdomen except Diplura.
- A total of 10 pairs are present in general, 2 pairs in the thorax and 8 pairs in the abdomen.
- Spiracles consist of sieve plates containing a large number of small apertures through which gas exchange takes place.e
- The hydrophobic nature of spiracles is due to the presence of modified epidermal glands known as peristigmatic glands which secrete a hydrophobe material preventing the wetting of these organs.
