Drosophila melanogaster

Table of Contents

• • • About Drosophila melanogaster
    • Taxonomy of Drosophila melanogaster
    • Drosophila melanogaster Features
    • Life Cycle of Drosophila melanogaster
    • Drosophila melanogaster Life Span – The Life Span of Fruit fly
    • Drosophila melanogaster Genes – Genetics of Drosophila melanogaster
    • Drosophila melanogaster Model Organism
    • Frequently Asked Questions

About Drosophila melanogaster

Drosophila melanogaster is a species of fly belonging to the order Diptera, family Drosophilidae. Often, the species are referred to as the lesser fruit fly or fruit fly or even vinegar fly. Colloquially, Drosophila melanogaster is referred to as fruit flies and remains the most commonly opted and used model entity in the fields of biomedical science.

Drosophila melanogaster or fruit flies inhabit a wide range of habitats. Their native habitats is that seen in tropical areas of the Old World. However, the common fruit fly has been observed in almost all the temperate regions of the world. The sole factor restricting them from inhabiting a region is the availability of water and temperature. Actually, the scientific name Drosophila refers to -lover of dew, and it implies that this species necessitates moist surroundings.

The factor of temperature highly influences the development of offspring of these species. The adults cannot tolerate the colder surroundings of high latitudes or high elevations. Additionally, there is a scarcity of food too in these regions. As a result, colder surroundings are not favourable for Drosophila melanogaster.

In various instances, the Drosophila can be seen in the fruit cellars or in other human-made structures with an abundant supply of food.

Taxonomy of Drosophila melanogaster

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Diptera

Family: Drosophilidae

Genus: Drosophila

Drosophila melanogaster Features

The common fruit flies usually have a tan (yellow-brown) in colour, and are close to 3 mm in length and 2 mm wide. It has a rounded head with red, large, compound eyes, three simple small eyes and short antennae. Their mouth is developed for sopping liquids. The female is somewhat larger compared to the males. On the dorsal side of their abdomen, black stripes are seen that discriminate between males and females. While males have a great quantity of black pigmentation, dense at the posterior end of the abdomen.

Life Cycle of Drosophila melanogaster

From the stage of egg fertilisation up to adult life, the life cycle of Drosophila lasts for close to 10 days at a temperature of about 25°C. It is a holometabolous insect with significant morphological variations between its larval and adult stages.

The life cycle of Drosophila comprises the following stages of development –

Embryogenesis

The life cycle begins with an egg. Here, the females lay white and small eggs, five at a stretch, on the delicate surfaces of the decaying matter seen in sinks, drains and dustbins.

This phase is rapid, lasting for 24 hours once fertilisation of the oocyte has occurred by the male gametes. A syncytial embryo quickly develops from the one-celled embryo. The quick DNA replication, as well as the nuclear divisions, occur in the early embryo syncytium, which generates close to 5000 nuclei for every embryo. Once nuclei migrate to the boundary of the syncytium, cellularisation takes place, which generates the syncytial blastoderm through the process of cleavage.

At the time of gastrulation, cells alter their shape and move, setting up the ectoderm, endoderm and mesoderm that are the layers of the body structure that will take place in the future.

Larva

There are 3 instars of larval stages spanning over 4 days approximately. At this time of growth, most of the types of cells are differentiated already and are operating, and a moulting shift takes place between the various larval stages.

Pupal phase

Once the encapsulation of the third instar larva has taken place, the pupal phase is initiated and persists for close to 4 days. Several structures of the larva are lysed, leading to the formation of new structures. These new structures are as a result of the formation of the imaginal disks, which grow from the undifferentiated cells of the larva.

These disks produce the adult head, wings, legs, thorax and reproductive structures. A few larval structures, such as the gonads or the nervous system, are conserved at the time of the pupal phase.

The eggs of the fruit fly hatch in a matter of a day or so, giving rise to cream-coloured larvae. The maggots quickly start to feed on the decaying material around them. The larvae, after five days of feeding on rotten garbage and ripen fruits, stick to a dry surface in the vicinity of a food source when it is about to pupate.

Adult phase

The fly in its adult stage appears once the pupal case ecloses. The female lays a higher number of eggs, about 100 eggs each day. This generates a major progeny, post the genetic cross takes place. This makes fruit flies a robust study model with easier growth under lab conditions.

Drosophila melanogaster Life Span – The Life Span of Fruit fly

The average lifespan of Drosophila approximately ranges between 10 and 50 days under optimal ambient temperature, and it is subject to vary. The female counterparts of fruit flies can mate and lay many batches of eggs in this period. This allows the population of fruit flies in a home to rapidly multiply. All in all, their life span is majorly influenced by temperature.

Drosophila melanogaster Genes – Genetics of Drosophila melanogaster

Drosophila melanogaster Chromosome Number

The genome of Drosophila comprises 4 pairs of chromosomes – three autosomes and an X/Y pair. The fourth chromosome, compared to the other, is smaller and hence is ignored usually, apart from their vital eyeless gene.

The sequenced genome of the 139.5 million base pairs has been interpreted, comprising approximately 15,682 genes as per a release. Apparently, greater than 60% of the genome constitutes non-protein-coding DNA (functional). These take part in gene expression control.

The process of sex determination in them takes place by the ratio X:A (X chromosomes to autosomes) and not due to the presence of the Y chromosome, as in the case of sex determination in humans. Despite the Y chromosome being completely heterochromatic, it comprises at least 16 genes, most of which are believed to have male-pertaining roles.

Drosophila melanogaster Model Organism

Typically, the Drosophila melanogaster finds use in the field of research courtesy of its rapid life cycle, comparatively simpler genetics comprising four pairs of chromosomes and a huge population of offspring in each generation. These are common pests in restaurants, homes, and other areas where food is found. Research on adult flies has resulted in significant discoveries in the field of basic biological mechanisms such as circadian clocks, ageing and even behavioural learnings.

These fruit flies have been widely used as model entities in genetics, in the fields of developmental biology, ageing and related areas of biomedical research for many years now. It is only in the recent past that a few researchers have started to take into account the versatility of Drosophila as a model organism in research pertaining to nutrition and food.

To summarise, fruit flies majorly comprise post-mitotic cells, having a brief lifespan, exhibiting eventual ageing. As seen in other species, the temperature has a huge impact on the life span of this entity. The restriction of calories has been observed to be a factor that extends their life span.

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