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Quantifying Drosophila food intake: comparative analysis of current methodology.

Deshpande SA, Carvalho GB, Amador A, Phillips AM, Hoxha S, Lizotte KJ, Ja WW - Nat. Methods (2014)

Bottom Line: Despite the prevalent use of Drosophila in laboratory research, precise measurements of food intake remain challenging in this model organism.We show that the CAFE and radioisotope labeling provide the most consistent results, have the highest sensitivity and can resolve differences in feeding that dye labeling and PE fail to distinguish.Understanding the strengths and limitations of methods for measuring food intake will greatly advance Drosophila studies of nutrition, behavior and disease.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, Florida, USA. [2].

ABSTRACT
Food intake is a fundamental parameter in animal studies. Despite the prevalent use of Drosophila in laboratory research, precise measurements of food intake remain challenging in this model organism. Here, we compare several common Drosophila feeding assays: the capillary feeder (CAFE), food labeling with a radioactive tracer or colorimetric dye and observations of proboscis extension (PE). We show that the CAFE and radioisotope labeling provide the most consistent results, have the highest sensitivity and can resolve differences in feeding that dye labeling and PE fail to distinguish. We conclude that performing the radiolabeling and CAFE assays in parallel is currently the best approach for quantifying Drosophila food intake. Understanding the strengths and limitations of methods for measuring food intake will greatly advance Drosophila studies of nutrition, behavior and disease.

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Comparison of feeding assays on flies of different gender and mating status. Feeding of males, virgin females, and mated females was measured using (a) dye-labeling, (b) 32P-labeling, (c) CAFE, and (d) PE. Flies (7–9 d old) were fed 2× medium (5% yeast extract + 5% sucrose). P values are shown (one-way ANOVA) and all significant pairwise comparisons are labeled (Tukey-Kramer post-hoc test for multiple comparisons): **, P < 0.01; ***, P < 0.001. Data shown are means ± s.e.m. (n = number of vials, shown in white over black bars).
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Figure 2: Comparison of feeding assays on flies of different gender and mating status. Feeding of males, virgin females, and mated females was measured using (a) dye-labeling, (b) 32P-labeling, (c) CAFE, and (d) PE. Flies (7–9 d old) were fed 2× medium (5% yeast extract + 5% sucrose). P values are shown (one-way ANOVA) and all significant pairwise comparisons are labeled (Tukey-Kramer post-hoc test for multiple comparisons): **, P < 0.01; ***, P < 0.001. Data shown are means ± s.e.m. (n = number of vials, shown in white over black bars).

Mentions: We sought to extend our comparative analysis using a different paradigm. Drosophila males ingest smaller volumes than females, and females eat more after mating14,31. We asked whether each technique can resolve these established feeding differences. With Canton-S, dye-labeling revealed a significant difference between males and mated females, but failed to differentiate between virgins and any of the other experimental groups (Fig. 2a). With Dahomey, no significant differences were seen. Both radioisotope-labeling and the CAFE showed significant differences between all groups for both strains (Fig. 2b, c). The PE assay revealed no differences in Canton-S, whereas Dahomey mated females showed significantly higher proportion feeding than males or virgin females, which did not differ between them (Fig. 2d). Collectively, these results confirm the conclusions of the compensatory feeding paradigm (Fig. 1)—that radiolabeling and the CAFE consistently have the highest resolving power. Dyes and PE can in some cases detect differences, whereas in others these assays miss dramatic behavioral changes, even when large numbers of replicates are used.


Quantifying Drosophila food intake: comparative analysis of current methodology.

Deshpande SA, Carvalho GB, Amador A, Phillips AM, Hoxha S, Lizotte KJ, Ja WW - Nat. Methods (2014)

Comparison of feeding assays on flies of different gender and mating status. Feeding of males, virgin females, and mated females was measured using (a) dye-labeling, (b) 32P-labeling, (c) CAFE, and (d) PE. Flies (7–9 d old) were fed 2× medium (5% yeast extract + 5% sucrose). P values are shown (one-way ANOVA) and all significant pairwise comparisons are labeled (Tukey-Kramer post-hoc test for multiple comparisons): **, P < 0.01; ***, P < 0.001. Data shown are means ± s.e.m. (n = number of vials, shown in white over black bars).
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Related In: Results  -  Collection

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Figure 2: Comparison of feeding assays on flies of different gender and mating status. Feeding of males, virgin females, and mated females was measured using (a) dye-labeling, (b) 32P-labeling, (c) CAFE, and (d) PE. Flies (7–9 d old) were fed 2× medium (5% yeast extract + 5% sucrose). P values are shown (one-way ANOVA) and all significant pairwise comparisons are labeled (Tukey-Kramer post-hoc test for multiple comparisons): **, P < 0.01; ***, P < 0.001. Data shown are means ± s.e.m. (n = number of vials, shown in white over black bars).
Mentions: We sought to extend our comparative analysis using a different paradigm. Drosophila males ingest smaller volumes than females, and females eat more after mating14,31. We asked whether each technique can resolve these established feeding differences. With Canton-S, dye-labeling revealed a significant difference between males and mated females, but failed to differentiate between virgins and any of the other experimental groups (Fig. 2a). With Dahomey, no significant differences were seen. Both radioisotope-labeling and the CAFE showed significant differences between all groups for both strains (Fig. 2b, c). The PE assay revealed no differences in Canton-S, whereas Dahomey mated females showed significantly higher proportion feeding than males or virgin females, which did not differ between them (Fig. 2d). Collectively, these results confirm the conclusions of the compensatory feeding paradigm (Fig. 1)—that radiolabeling and the CAFE consistently have the highest resolving power. Dyes and PE can in some cases detect differences, whereas in others these assays miss dramatic behavioral changes, even when large numbers of replicates are used.

Bottom Line: Despite the prevalent use of Drosophila in laboratory research, precise measurements of food intake remain challenging in this model organism.We show that the CAFE and radioisotope labeling provide the most consistent results, have the highest sensitivity and can resolve differences in feeding that dye labeling and PE fail to distinguish.Understanding the strengths and limitations of methods for measuring food intake will greatly advance Drosophila studies of nutrition, behavior and disease.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, Florida, USA. [2].

ABSTRACT
Food intake is a fundamental parameter in animal studies. Despite the prevalent use of Drosophila in laboratory research, precise measurements of food intake remain challenging in this model organism. Here, we compare several common Drosophila feeding assays: the capillary feeder (CAFE), food labeling with a radioactive tracer or colorimetric dye and observations of proboscis extension (PE). We show that the CAFE and radioisotope labeling provide the most consistent results, have the highest sensitivity and can resolve differences in feeding that dye labeling and PE fail to distinguish. We conclude that performing the radiolabeling and CAFE assays in parallel is currently the best approach for quantifying Drosophila food intake. Understanding the strengths and limitations of methods for measuring food intake will greatly advance Drosophila studies of nutrition, behavior and disease.

Show MeSH