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Effect of Low Pressure on Ovarian development in Drosophila melanogaster

Global surface temperatures that have been rising steadily over recent centuries, largely due to anthropogenic carbon emissions, are extending the potential habitat ranges of insect disease vector populations into higher altitudes. While a number of investigations have examined the effect of low oxygen levels on development and gene expression, we are unaware of any that have examined this using air at low pressure rather than via novel gas mixes. We exposed newly eclosed fruit flies (Drosophila melanogaster) to a low-pressure environment equivalent to an altitude of approximately 6,000m above sea level in a custom-built hypobaric chamber. This altitude approximates the highest permanent human habitations in the Himalayas, an area where climate change is having profound effects. The chamber was housed at 26oC in a photoperiod of L12:D12 to examine the effects of hypoxia due to low pressure on ovarian development; a control group was maintained under the same conditions at ambient pressure (sea level). Ovaries were removed 36h post eclosion and examined for size and the extent of egg development. The ovaries are now stored in RNAlater® for subsequent RT-PCR analysis of the expression of hypoxia inducible factors and those genes involved in yolk protein synthesis and trafficking. Our investigation revealed no difference in ovarian length or width attributable to the low-pressure environment (p=0.176 and 0.484 respectively) indicating at least tentatively that these environments are a possible habitat for invasive insect populations. Similar experiments to determine fecundity and reproductive timing of Drosophila development under these conditions are ongoing.