Physiology: fruit flies

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Physiology: fruit flies
Physiology: fruit flies

Dropfly ventilation via proboscis

Dross flies can breathe better during flight with the help of their proboscis, reports researchers from the University of Ulm. With contractions of the oral apparatus, which is specialized in sucking liquid food, the insects ventilate their tracheal system and thus ensure better transport of oxygen to the working cells.

In insects, tracheae form a gas-filled tube system whose ramifications supply each cell with oxygen and carry away the carbon dioxide produced during respiration. The insects, on the other hand, lack a blood vessel system in which gas transport molecules such as hemoglobin circulate. For a long time it was assumed that the gas exchange in the tracheal system must take place purely passively through diffusion.

Later on, entomologists recognized various ways in which insects could selectively circulate the gas content in their air-filled, sac-like trachea. For this purpose, many larger insects pump their body fluids through muscle contractions, opening and closing different valve flaps between the trachea and the outside air, resulting in a directed air flow. The animals can also adapt the performance of the respiratory system to their activity and oxygen consumption.

Fritz-Olaf Lehmann and Nicole Heymann have now discovered a previously unknown way of ventilating fruit flies: the animals emit large amounts of carbon dioxide for short periods at regular intervals during their constant, energy-intensive activity. The animals' trunks in particular moved, as camera recordings showed. At the same time, the insects also control the opening of their four pairs of tracheal openings, which, according to the results of a computer simulation, should also contribute to more even ventilation.

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