Gas Exchange in Locusts

“How Locusts Breathe”

The main objective of the article is to investigate the means by which gas exchange occurs in the locust, with regards to possible implications for the development of microfluidic systems in the biomedical engineering field. The locust tracheal system has a complex morphology, consisting of longitudinal tracheal trunks, supported by taenidia, rings of thickened cuticle that resist compression and expansion. Transverse tracheal branches connect ten pairs of segmental spiracles to the longitudinal tracheae, and finer tracheae branch from both the transverse and longitudinal trunks to the tissues for gas exchange. Flexible air sacs connect the tracheae and spiracles throughout the body, and allow for freedom of movement during muscle contraction. The tracheal systems within the abdominal, thoracic, and head regions are largely distinct from one another; the resulting disparity in local air flow presents a particular challenge to researchers, and is the major focus of this article. Additionally, respiration occurs by different means, and at different rates, depending on the animal’s present physiological and environmental state.

Air flow within the locust is unidirectional: normal inspiration is via the first four pairs of spiracles, which remain open during expansion of the abdomen, and expiration is via the posterior six pairs of spiracles, which open during abdominal compression. During flight however, spiracles 1 and 4-10 remain synchronized with abdominal pumping, but spiracles 2 and 3 are kept open to allow tidal ventilation of flight muscle, as contraction is associated with thoracic volume changes. Furthermore, this pattern can be altered during any time of increased activity and respiratory drive, changing the number of spiracles open, as well as the percent of time in the respiratory cycle each pair remains open. Insects have the capacity for discontinuous gas exchange (DGE), during which all spiracles remain closed, and...