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Using confocal imaging to understand the effect of atmospheric oxygen on insect respiratory systems
Author(s) -
Gstrein Gregory,
Arthur Kathryn,
Parker Greg,
Friedman Jessica,
Brooks John Vanden
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.760.15
Subject(s) - oxygen , insect , hyperoxia , respiratory system , biology , biophysics , biological system , ecology , anatomy , chemistry , organic chemistry
Recent geochemical models suggest that over geologic time atmospheric oxygen has varied from as low as 12kPa and as high as 31kPa. These changes in atmospheric oxygen would have had strong effects on the physiology and evolution of organisms living at those times including insects and other arthropods. Insects transport oxygen completely in the gas phase through hollow tubes known as tracheae. We have hypothesized that this unique respiratory system of insects made them more susceptible to changes in atmospheric oxygen. Previously, it has been shown that as insects increase in body size, their tracheal system increases at a faster rate and may eventually limit the maximum body size of insect species. As a corollary, we have shown that rearing oxygen is inversely correlated with tracheal system density in some insects; with hyperoxia decreasing tracheal investment and hypoxia increasing tracheal investment. Therefore, a hyperoxic rearing environment may remove the spatial constraint of the tracheal system and allow insects to achieve larger body sizes. However, a limit to these studies has been a focus on the large conducting tracheae which drive bulk flow of gases through the system. Previous research has largely ignored the final oxygen delivery component of the tracheal systems. Here we look at the effect of rearing oxygen on the smallest components of the tracheal system – the blind ended tracheoles across which the actual oxygen delivery to the tissues occurs. To this end, we have developed a new confocal imaging technique to image and analyze insect tracheoles in 3D, which allows for increased resolution and spatial imaging capability. The density of tracheoles, tracheolar diameters, and network properties of the tracheolar branching all affect oxygen delivery and may be a major driver in the control of insect body size. To understand these effects, we reared Drosophila melanogaster under three different oxygen partial pressures (12kPa ‐ hypoxia, 21kPa ‐ normoxia, and 31kPa hyperoxia) that match the range of variation seen over geologic time. We then carried out confocal imaging of the tracheolar network in the flight muscle dissected out of the thorax of these D. melanogaster . The tracheolar network auto‐fluoresces under the confocal microscope excitation allowing us to obtain high resolution 3D reconstructions of the respiratory system. By using ImageJ and AVIZO, we were able to measure tracheal and tracheolar diameters and characterize the network branching patterns of these D. melanogaster reared under the varying oxygen levels. By measuring these two components of the insect respiratory system, we have shown that oxygen does effect tracheolar diameters and has a strong effect on branching pattern and tracheolar investment in the flight muscle of D. melanogaster . Support or Funding Information Midwestern University College of Veterinary Medicine Fellowship Program