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Reproduction Of Drosophilia Melanogaster
Introduction I will be conducting an experiment to figure out whether or not the amount of medium in a vial will affect fruit fly reproduction. During the experiment I will be counting the number of fruit flies at one week intervals and observing the following: 1. are a greater number of fruit flies in the vials with a larger amount of medium, 2. are a greater number of fruit flies in the vials with lesser amount of medium, 3. is the number of fruit flies in the vials the same, regardless of the amount of medium. There is a great importance in this experiment. During the 1970's and 80's, the Mediterranean fruit fly invaded the United States. This fruit fly drills its sharp ovipositor into ripe plants, and then deposits her eggs there. After about a week or two these eggs develop into larva, which burrow through the fruit, damaging the fruit and making it unable to be sold. This badly damaged the United State's agricultural economy. Soon after, worldwide quarantines were put on the rapine fruit fly (Foote, 1993). Therefore, the importance of this experiment is to determine whether or not the amount of food available for the fruit fly increases their reproduction. I will ascertain this by keeping the red-eyed pomace fly, Drosophilia Melanogaster, (Mediterranean fruit flies are illegal to keep in the United States) in varying heights of medium, 3/4 inches and 1 1/2 inches. If there are more fruit flies in the 3/4 inch vials, then we know that the less food equals more fruit flies. If there are more fruit flies in the 1 1/2 inch vials then we know that more food equals more fruit flies. Or, if there are equal amounts of fruit flies in both heights of vials then we know that it doesn't matter how much food there is, there will still be the same amount of fruit flies. By using this information, farmers may be able to stop further fruit fly invasions. Fruit flies belong to the order Diptera and constitute the family Tephritidae (Webster, 1988). They are two-winged flies, whose larvae feed on fresh or decaying vegetable matter. The Drosophilia Melanogaster lays its eggs on decaying fruit and therefore has no need for a sharp ovipositor and doesn't cause agricultural destruction (Encarta, 1995). The reproductive cycle of Drosophilia Melanogaster, from egg to larva to adult, lasts about two weeks (Highnam, 1963). It all begins in the ovary. Each ovary has sixteen ovariolees, which are egg assembly lines (see Figure 1A). Each ovariole has a germarium, which is the place egg chambers develop (see Figure 1B). Each egg chamber has a large nucleus called an oocyte, around fifteen nurse cells, and 1000 follicle cells, which protect and nourish the egg. During the development of the egg chamber an eggshell, called the chorion, forms (see Figure 1C). On the exterior of the anterior part of the egg two dorsal extensions form. These will assist the fruit fly embryo in breathing once the egg is fertilized. Just below the two extensions is the operculum. This is the exit for the embryo, once it has reached the larval stage. Underneath the operculum is the micropyle, which is the entryway for the sperm (see Figure 1D). Once the egg chambers are fully developed they leave the germarium and move posteriorward in linear order. Most developed to least developed, with the aid of rhythmic muscular contractions from the ovarian wall and end up the uterus (see Figure 1B) (Bate and Arias, 1993). Figure 1 If the egg isn't fully developed while sexual intercourse is occurring between the male and female fruit flies, then the sperm will be kept in a minute space in the forward portion of the uterus (Engleman, 1970). Once the egg is fully developed and ready to be fertilized the sperm are released. After the egg has been fertilized the female deposits the eggs on the rotten fruit or vegetable (Kaulenas, 1992) (see Figure 2). Within around a week, a larva crawls out of the egg and burrows through the rotten matter and begins to molt. It will molt twice while inside the medium (Sonnenblick, 1965). Four days later, the larva crawls out of the medium, attaches itself to a dry surface and forms into a pupa. After three more days an adult or imago D. Melanogaster will emerge (Ward's lab, 1994). Figure 2 The objective of my experiment is to determine whether or not the amount of medium (food) in a vial affects the reproduction of fruit flies. My hypothesis is that there will not be a difference in the quantity of fruit flies. I believe that here will not be a difference because the fruit flies cannot eat 1 1/2 inches of medium, let alone 3/4 of an inch of medium. They will not need that much medium, and therefore will technically have the same amount of medium. Materials and Methods The first step involves the preparation of the fruit fly medium. To make 7.5cm of medium, place a 113.4gram. vial, base down, next to a ruler and add 3.75cm of Ward's instant Drosophilia medium into the vial. Do this by dipping a spoon, does not have to be sterile, into the jar of Ward's instant Drosophilia medium and putting into the vial. After each spoonful of medium, tap the vial until the medium is relatively flat. After there is 3.75cm of medium in the vial, add 3.75cm of distilled water into the vial (see Figure 1). Figure 1 Repeat these steps for three other vials. To make 15cm of medium, perform the same steps but use 7.5cm of instant medium and 7.5cm of distilled water. After all of the vials have medium in them, 4 vials with 7.5cm of medium in them and 4 vials with 15cm of medium in them, allow them to sit overnight to let the medium soak up the distilled water. The second step in my experiment was to introduce the fruit flies into the vials containing the medium. First, place one vial of wild type fruit flies or yellow white fruit flies into the freezer until all fly motion has ceased (around 5 minutes)(see Figure 2). Figure 2 Remove the vial from the freezer, uncap it, and turn it upside down and let the fruit flies out onto a white surface. Working as quickly as possible put 20 live fruit flies into a vial with 7.5cm medium by moving them carefully with a camel's hair brush. The fruit flies are dead if they carry their wings vertically. If the fruit flies are alive they carry their wings horizontally. If there aren't enough flies for that vial, use flies from another vial until there 20 in that vial. If there are extra flies, use them in another vial. After there are 20 fruit flies in a 7.5cm vial put that vial aside. Repeat these steps except put 10 fruit flies in a vial with 7.5cm medium in it. Repeat these steps for the vial with 15cm medium in it. Repeat the preceding steps for the yellow-white fruit flies. The vials have 10 fruit flies and others have 20 fruit flies to see if the fruit flies need a higher or lower population to breed more successfully. After all 8 vials have the according number of fruit flies and height of medium in them (4 vials with 7.5cm medium and 4 vials with 15cm medium in them) label them with the amount of fruit flies in them, the height of the medium, and the date the flies are put into medium. At weekly intervals the flies should be put into the freezer, counted on a white surface, and returned to their vials. Record the number of fruit flies in vial on a chart that is similar to Figure 1 (also make one for the yellow-white fruit flies). One chart for the Wild Type fruit flies and one for the Yellow-White fruit flies. Drosophilia Population Count Wild Type (+) Fruit Flies Date: Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 7.5cm media 5 pr 10 pr 15cm media 5 pr 10 pr Figure 3 Continue this for eight weeks, 4 generations of fruit flies, always making sure the intervals between counting is the same. The vials should be stored in a safe place that does not receive direct sunlight for long periods of time and has a constant temperature of around 39 degrees Celsius such as styrofoam vial holders I used (see Figure 4). Figure 4 A thermometer should be kept by the fruit flies and checked every day. It is does not hurt the fruit flies to be exposed to total darkness. Figure 5-some necessary materials. From left to right:Styrofoam vial holder, instant drosophilia medium, magnifying glass, 113.4 gram vial cap, styrofoam plug, 113.4gram vial, camel hair brush and fruit flies Results In this experiment to find whether the amount of medium affects Drosophilia Melanogaster reproduction, the data collected reveals that the amount of medium does affect Drosophilia Melanogaster reproduction. Chart 1 shows the exact data. In the vials with 3/4" medium the Drosophilia Melanogaster population drops slightly between the first and second week, then as the first new generation hatches the Drosophilia Melanogaster population jumps upward. The fly population then drops between the third and fourth weeks, except in the case of the vials with 5 pairs of Yellow-White fruit flies. By the fifth week the 3/4" fruit fly population is dwindling, and by the sixth week all of the fruit flies have perished. In the vial with 1 1/2" medium there was an immediate jump in the 5 pair Yellow-White fruit flies and a very slight drop in fruit fly population from first week to the second week. With the Wild-Type fruit flies their population continued to rise until the fifth week, when a slight population drop occurred. From the fifth week to the sixth week the population continued to rise. With the 5 pair Yellow-White fruit flies their population their population rose from Week 1 to Week 6. With the 10pr Yellow-White fruit flies their population continued to increase nonstop from Week 1 to Week 6. Drosophilia Population Count Wild Type (+) Fruit Flies Date: Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 3/4" media 5 pr 10 9 53 21 9 0 10 pr 17 13 49 35 19 0 1 1/2" media 5 pr 6 22 44 47 41 68 10 pr 14 12 41 56 43 61 Yellow-White Fruit Flies Date: Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 3/4" media 5 pr 9 8 19 32 1 0 10 pr 11 10 36 22 11 0 1 1/2" media 5 pr 6 15 28 29 43 45 10 pr 15 13 32 37 46 54 Chart 1 Drosophilia Population Graphs


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