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Aspirator used to remove flies from traps
Fruit Fly Traps and the Stevison Lab
Fruit Fly Traps and the Stevison Lab
Welcome! You may have found this page by scanning the QR code from one of our traps around town. So, that means you are curious about:
- What happens next?
- And, what we are doing?
From the traps, we will collect the flies. To do this, we aspirate them from the traps (left) and switch them to fresh food vials to be transported back to the laboratory, where they will be identified using established species keys. Females identified as Drosophila robusta (right) will be individually isolated to look at the chromosomes in their offspring (more below).
Drosophila robusta
Polytene chromosomes of D. robusta
Polytene chromosomes
Polytene chromosomes
The salivary glands of Drosophila undergo many rounds of mitosis without cell division resulting in chromosomes that are visible under a microscope, called “polytene chromosomes”.
This method birthed the field of comparative genomics in Drosophila in the 1940s and allowed for the discovery of naturally occurring chromosomal inversions. Among Drosophila species, at least 60% are naturally polymorphic for chromosomal inversions. The frequencies of these inversions often show geographic and altitudinal clines, as well as cyclic and long-term temporal changes.
Polytene chromosome images are prepared from a 3rd-instar larva (yes, that is the scientific term for "maggots").
A 70 year comparison of allele frequencies in Drosophila robusta
A 70 year comparison of allele frequencies in Drosophila robusta
As part of a PhD dissertation project, we are setting up a study to compare the frequency of chromosomal inversion polymorphisms between a study conducted in 1949 (shown in purple in image to the left) and now. This comparison will be used to measure how climate change has impacted these organisms in the 70 years between studies. Our first goal is to collect in and around Auburn and establish stocks of this species in our lab. We plan to expand our collections across the state as part of a citizen science project to get comparison data for each of the collection sites from 1949.
D. robusta is a forest species found easily in state parks, and is endemic to Alabama. This species of fruit fly is abundant during the warm months of the year and its distribution superimposes strikingly on that of the American Elm. We are doing regular collections, setting up traps with ripe bananas as bait, suspended from American Elm trees, ~10-25 feet apart (see above).
Once we have females, we will let them lay eggs to get their larvae. The larvae will be used to examine polytene chromosomes (see above). A salivary gland preparation will be made from a single 3rd-instar larva, and aceto-orcein will be used to stain the chromosomes. If you want to learn more, here is a video of this process.
High resolution photographs of all slides will be maintained for direct comparison. The photos of their chromosomes will be used to get a measure of inversion polymorphism frequencies in present day populations of this species.
For more information on this project, please contact the Project Leader, Natalia Rivera Rincon, a PhD student in the Stevison Lab.
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