About Lesson
RESPIRATORY SYSTEM OF INSECTS
Insects do not bear highly developed organs and they respire through air tube called tracheal system.
A) Tracheal system (trachea and tracheoles):
- In insects, exchange of gases takes place through tubular structures, called trachea.
- The trachea are divided in to 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 closed tracheal system.
- Tracheoles form a network over the visceral organs including the alimentary canal as well as the gonads (ovaries, testis) and penetrate in to the tissues of the organs and become intracellular and supply oxygen directly to the tissues.
Difference between trachea and tracheloles
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Trachea |
Tracheoles |
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a. These are large tubes running from spiracles. |
a. Fine tubes arising distally from trachea. |
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b. Taenidia present |
b. Absent |
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c. Intima layer is shed during moulting. |
c. Intima layer retained or unchanged during moulting. |
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d. Never become intra cellular |
d. Intracellular |
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e. Intima layer consist of 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 prothorax and distributed in meso, metathorax and abdomen except Diplura.
- A total of 10 pairs are present in general, 2 pairs in thorax and 8 pairs in abdomen.
- Spiracles consists of sieve plate containing large number of small apertures through which gas exchange takes place
- 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.