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Introduction
Fruits flies or Drosophila melanogaster nourish on the fungi and bacteria present on rotting fruit. They have a unique capability of tracking food via remote chemoreception while flying and landing. Once they sense the smell of the food, they continue to hunt for it on the ground. This behavior is termed as foraging, and it is dependent on the process of chemoreception (Bateman, 1972). Flies possess chemoreceptors in the front pair of legs to sense such unique sensations, which facilitate them to discover or taste the substance of the bedrock on which they walk or stay. When they sense an appropriate source of food, they expand their proboscis appendages to take their feed. If the source of food was not sufficient to them and they cannot satiate on them, they start searching again on the ground. This behavior is called foraging. It is just a walking mode but delivers high turning rates through a slow rate of locomotion. Through this behavior flies stay in the territory of food. Drosophila has a single gene responsible for foraging that is “for” gene; that presents the best examples of a simple gene that deals with complicated behavior (Aracena, 2011). Molecular mapping technique has positioned mutations of the gene “for” in dg2 gene class that encodes a cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG) enzyme (Pereira & Sokolowski, 1993). It is observed that Rovers possess high PKG activity in comparisons of sitters which may be due to behavioral polymorphism among wild-type flies that brought a natural variation of PKG activity (Davies, Krebs & West, 2012).
This experiment is designed to understand the food selection behavior of flies. For the experiment, the fruit flies were kept hungry for 24 hours and provided with water. An inclusion of 0.25 µL of 250 mM sucrose in the vicinity will stimulate the local search. The ingestion rates for various sugars differ. A two-choice test was conducted to determine their choice to assess their feeding preferences. According to Aracena, (2011) flies prefer sucrose over glucose and fructose and these both are preferred over lactose and mannose. The concentration of glucose solutions also determines the choice pattern as high concentrations are very gelatinous and thus difficult to digest, while lower concentrations enforce excitatory effects.
Feeding selection of Flies is also modulated by excitatory and inhibitory effects of the food. Hunger plays the role of the best excitatory signaling and Quinine acts as a powerful deterrent. 48 hours food deprived flies will feed on sucrose. Now the main question is whether hungry (apterous) fruit flies prefer real banana (solution) or banana-flavored sugar (solution).
“It is hypothesized that there is no difference between their choices of food over real banana, and banana flavored sucrose.”
In this experiment, two choices were given to the flies, real banana solution, and banana flavored sugar solution. The provided real banana solution was colored red, and the banana sucrose solution was blue in color. Hungry flies were placed in the foraging arena and were allowed to nourish for 60 minutes. The data was collected at frequent intervals.
Results
Figure 1: Petridish with foraging arena
Figure 2: Microscopic demonstration of fruit flies. The color of their abdomens shows that flies with red and blue abdomen nourished on only red and blue food, respectively, while purple fly shows ingestion of both.
Below are the tables showing gathered data from the test.
According to the table of final feeding preferences: total flies= 220
Expected as hypothesized= 110 on each group
(Half on banana and half on banana sucrose, as hypothesized flies have no preference.)
Chi-square X2 value from the data is = 69.55
Degrees of freedom= 3
The P-Value is < 0.00001. The significance value p is smaller (p < 0.05), thus the null hypothesis is rejected. It seems that there are several other determinants that determine the choice of food as seen in the data the flies preferred real banana solutions over sucrose solution.
Discussion
We have given a null hypothesis claiming that there is no difference in the feeding preferences over the real banana solution and banana flavored sucrose solution. The data showed that flies preferred real banana over sucrose solution. There may be various factors that worked behind negating the hypothesis. It also can be seen that a prominent number did not eat both of the given options. On calculating the significance value from the data tables the significance value p was quite low that drove to the rejection of the null hypothesis (Anderson et al., 2000). It was already stated that flies prefer sucrose over glucose, fructose, and mannose. But in this experiment the flies did not attract towards sucrose, instead they preferred real banana. Some of them even did not feed on anything while a major amount nourished on both. According to the literature, the flies prefer sucrose over others but the findings are distinct in this case revealing new phenomenon of incidence (Aracena, 2011; Prokopy & Roitberg 1984).
The experiment results are significant because foraging is a locomotory skill of fruit flies that indicates a lot about their nature, feeding habits, and egg-laying patterns. It is not a relation of their habits and eating preferences, but it is attributable to the existing different alleles located at the similar genetic locus of the behavioral gene “for” responsible in foraging. This gene helps in understanding the genetic source and evolutionary consequence of a behavioral polymorphism. It is seen that Rover allele, forR locomotes faster while foraging in comparison of alleles with homozygous pairing (fors). This difference due to allelic variations results in the activity of adults which is primarily originated from allelic differentiation at the foraging genetic site (Pereira & Sokolowski, 1993; Prokopy & Roitberg 1984). The shortcoming of the experiment may be the unexpected error while making the solutions that impact the feeding pattern of flies, as many of them did not feed any solution. For the future research purpose these steps of making solutions can be followed more cautiously.
References
Aracena, J. (2011). Using Foraging Behavior of Fruit Flies to Introduce Undergraduates to
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Anderson, D. R., Burnham, K. P., & Thompson, W. L. (2000). Null hypothesis testing:
problems, prevalence, and an alternative. The journal of wildlife management, 912-923.
Bateman, M. A. (1972). The ecology of fruit flies. Annual review of entomology, 17(1),
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Davies, N. B., Krebs, J. R., & West, S. A. (2012). An introduction to behavioural ecology. John
Wiley & Sons.
Pereira, H. S., & Sokolowski, M. B. (1993). Mutations in the larval foraging gene affect adult
locomotory behavior after feeding in Drosophila melanogaster. Proceedings of the
National Academy of Sciences, 90(11), 5044-5046.
Prokopy, R. J., & Roitberg, B. D. (1984). Foraging behavior of true fruit flies: concepts of
foraging can be used to determine how tephritids search for food, mates, and egg-laying
sites and to help control these pests. American Scientist, 72(1), 41-49.
