THE PLASTIC NATURE OF THE INSECT TRACHEAL SYSTEM

The insect tracheal system is a network air filled tubes that provide the cells and tissues with oxygen, and like the human respiratory system, eliminates carbon dioxide as a product of cellular respiration. The network of tubes branches throughout the insect’s body and connects directly to the muscles and other energy extensive areas. For those who do not know much about insects, they do not breathe through their mouths. Air is inhaled and exhaled through openings in the cuticle called spiracles, which are located on the thorax and abdomen. Thoracic spiracles are involved in inhalation while abdominal spiracles are involved in exhalation.

During the life cycle of insects especially in those that are holometabolous (larva->pupa->adult) the tracheal system faces various challenges. It has to be plastic enough to adapt to different changes in the insect during growth, ranging from a simple posterior to anterior tube as a larva to a highly branched tubular system that is connected to muscles such as ones for flight. To understand these changes, the effects of oxygen deprivation are considered. In the 1950’s Sir Vincent Wigglesworth, a pioneer of insect physiology demonstrated that hypoxia in Rhodnius (kissing bug) mediated the plasticity of the tracheal system. By managing to surgically cut the trachea of certain segments of the kissing bug, he noticed that the tracheal branching from anterior and posterior sections migrated to areas of hypoxia. This experiment was followed by transplanting certain organs that required lots of oxygen to areas of hypoxia, which resulted in a similar response. Thus, these findings demonstrate how insects are capable of coping with environmental variation.

Posted by Nelson Milano (2)