The life cycle of Drosophila melanogaster at 25 °C takes only 2 weeks; everything takes about twice as long at 18 °C. Females lay some 400 eggs (embryos) into rotting fruit or other organic material. The eggs, which are about 0.5 millimetres long, eclose after 24 h. The resulting larvae grow for 5 days whilemolting twice, at about 24 and 48 h after eclosion. During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit themselves. Then the larvae encapsulate in the puparium and undergo a five-day-long metamorphosis, after which the adults emerge. Females first mate about 12 hours after emergence. The females store spermfrom previous males they mated with for later use. For this reason geneticists must collect the female fly before her first mating, that is, a virgin female, and ensure that she mates only with the particular male needed for the experiment. Inseminated females can be "re-virginized" by prolonged incubation at -10 °C, which kills the sperm, according to Michael Ashburner's "red book". There are four stages in the life cycle of the fruit fly: egg, larva, pupa, and adult. At a typical classroom temperature (21 C), Drosophila melanogaster will produce new adults in two weeks; eight days in the egg and larval stages, and six days in the pupal stage. The life span of a fruit fly may be several weeks. Twenty-four hours after the egg is laid, the larva hatches. The larva has two molting periods, during which the cuticle, mouth, hooks, and spiracles are shed. The larva is called an instar during the periods of growth before and after molting. Thus, the fruit fly has three instars. The puparium develops from the third instar which becomes hard in texture and dark in color. The puparium is where metamorphosis takes place. Just before the adult fly emerges from the puparium, the pupa darkens. Approximately 24 hours before the adult fly emerges, one can see the folded wings and the pigment of the eyes if one looks closely through the puparium. Upon completion of metamorphosis, the adult forces its way through the operculum (anterior end) of the puparium. Initially the fruit fly appears light in color with a long abdomen and unexpanded wings. In just a few hours the fly gets darker in color, rounder in the abdomen and extends its wings. Approximately 48 hours after emerging from the puparium, it is possible for females to start laying eggs. However, there are only 12 hours that a female can be considered virgin after emerging as an adult. After reaching this maturity, the flies are fertile for life. A female fruit fly can store sperm after a single insemination and use it for many reproductions; therefore it is important to use virgin females for genetic crosses.
Drosophila: Life Cycle
Scientists study Drosophila as a model specimen because of their very short life and reproduction cycle. In fact, their life cycles only last about 14 days! Since fruit flies don't live forever, reproduction is critical to keep the species alive. Are you familiar with a butterfly's life cycle? If so, you'll see that Drosophila's life cycle is very similar to a butterfly's. They both undergo complete metamorphosis, which means that the young form looks very different from the adult! Unlike baby humans, who have all of their adult structures (arms, legs, fingers, nose, etc.) and look like small versions of adults, the baby fruit fly looks very different from the adult. The baby, or larva, looks like a small worm, and does not have adult structures like wings or legs. Like many species, female fruit flies produce eggs and males produce sperm. When the egg and sperm unite, a new individual develops. In fruit flies, sperm is deposited from the male fruit fly into the female fruit fly. The female stores sperm inside of her. The eggs are fertilized when they pass through the oviduct on their way to being deposited on a food source. Fruit flies begin their lives as an embryo in an egg. This...
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