Fluctuating asymetry of wing vein traits in the fruit flies (Drosophila melanogaster) exposed to sidestream cigarette smoke.

Abstract

Insect wing veins are important structures that easily respond to stressors like sidestream cigarette smoke. Developmental instability caused by these stressors can manifest as fluctuating asymmetry (FA), or random deviations from bilateral symmetry. This study aimed to investigate the effect of sidestream cigarette smoke on selected quantitative wing venation traits of Drosophila melanogaster. Cultures of D. melanogaster were maintained at 27°C, and the set-up was separated into smoke-exposed (SE) and non-smoke exposed (NE) groups. Morphometric analysis of the wing vein traits of the female flies showed four traits did not exhibit FA for the NE group. These traits are found along the diagonal connecting the costal vein to the margin of the posterior-most vein, suggesting a need to preserve the proximal rigidity of the wing. All other measured traits exhibited FA. Notably, three traits found at the distal end of the wing were found to exhibit higher FA values compared with the SE group. These differences in presence and magnitude of FA for different regions of the wing suggest a modular type of development in D. melanogaster wings. Of the 35 traits, 32 traits possessed higher FA for the SE group compared to the NE group. These results suggest that smoke stress affects the growth of the wing as a whole. However, because the distal wing vein traits showed lower FA for the SE group compared to the NE group, it may be hypothesized that there is a buffering mechanism present that tends to preserve the development of the distal compartments. Sidestream cigarette smoke exposure will increase the FA exhibited by fruit fly, thus, the use of Drosophila melanogaster as a bioindicator is helpful. The most practical measurement is possible for those traits that are found to be on the proximal end of the wing as these are well conserved.