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Drosophila

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Drosophila is a genus of small flies whose members are often called small fruit flies, or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies. A second insect family, the Tephritidae are also called fruit flies; they feed on unripe or ripe fruit. One species in particular, Drosophila melanogaster, has been heavily used in research in genetics and is a common model organism in developmental biology. Indeed, the terms "fruit fly" and "Drosophila" are often used synonymously with D. melanogaster in modern biological literature. The entire genus, however, contains about 1,500 species and is very diverse in appearance, behavior, and breeding habitat.

Contents

Name

The term "Drosophila" is a modern scientific Latin adaptation from Greek δρόσος, drósos, "dew", + φίλος, phílos, "loving" + Latin feminine suffix -a.

Morphology

Side view of head showing characteristic bristles above the eye.
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Side view of head showing characteristic bristles above the eye.
D. setosimentum, a Hawaiian picture-wing species.
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D. setosimentum, a Hawaiian picture-wing species.

Drosophila are small flies, typically pale yellow to reddish brown to black, with red eyes. Many species, including the noted Hawaiian picture-wings, have distinct black patterns on the wings. The plumose (feathery) arista, bristling of the head and thorax, and wing venation are characters used to diagnose the family. Most are small, about 2-4 mm long, but some are larger than a house fly.

Life cycle and ecology

Habitat

Drosophila are found all around the world, with relative more species in the tropical regions. They can be found in deserts, tropical rainforest, cities, swamps, and alpine zones. Some northern species hibernate. Most species breed in various kinds of decaying plant and fungal material, including fruit, bark, slime fluxes, flowers, and mushrooms. A few species have switched to being parasites or predators. Many species can be attracted to baits of fermented bananas or mushrooms, but others are not attracted to any kind of baits. Males may congregate at patches of suitable breeding substrate to compete for the females, or form leks, conducting courtship in an area separate from breeding sites.

Several Drosophila species, including D. melanogaster, D. immigrans, and D. simulans, are closely associated with humans, and are often referred to as domestic species. These and other species (D. subobscura, Zaprionus indianus) have been accidentally introduced around the world by human activities such as fruit transports.

Reproduction

Drosophila melanogaster egg
Drosophila melanogaster egg

Drosophila vary widely in their reproductive capacity. Those such as D. melanogaster that breed in large, relatively rare resources have ovaries that mature 10-20 eggs at a time, so that they can be laid together on one site. Others that breed in more-abundant but less nutritious substrates, such as leaves, may only lay one egg per day. The eggs have one or more respiratory filaments near the anterior end; the tips of these extend above the surface and allow oxygen to reach the embryo. Larvae feed not on the vegetable matter itself but on the yeasts and microorganisms present on the decaying breeding substrate. Development time varies widely between species (between 7 and more than 60 days) and depends on the environmental factors such as temperature, breeding substrate, and crowding.

Many species are easily reared in the laboratory; D. melanogaster is ideal experimental animal because of this. Others, breeding on a specific host in the wild, are difficult to breed in the lab. For some it can be done with particular recipes for rearing media, or by introducing chemicals such as sterols that are found in the natural host; for others it is (so far) impossible. In some cases, the larvae can develop on normal Drosophila lab medium but the female will not lay eggs; for these it is often simply a matter of putting in a small piece of the natural host to receive the eggs.

Predators

Drosophila are prey for many generalist predators such as robber flies. In Hawaii, the introduction of yellowjackets from the mainland United States has led to the decline of many of the large species. The larvae are preyed on by other fly larvae, staphylinid beetles, and ants.

Systematics

The genus Drosophila contains about 1,500 species and is highly paraphyletic; it represents a generalized form from which a number of distinctive offshoots, which have been named genera, have arisen. The majority of the species are members of two subgenera: Drosophila (~1,200 species) and Sophophora (including D. (S.) melanogaster; ~325 species). About 250 species are part of the genus Scaptomyza, which arose from the Hawaiian Drosophila and later re-colonized continental areas. The Hawaiian species of Drosophila (500+, with ~375 species described) are sometimes recognized as a separate genus or subgenus, Idiomyia, but this is not widely accepted.

Evidence from phylogenetic studies suggests that the following genera arose from within the genus Drosophila:

Solving the paraphyletic status of the genus Drosophila without changing the name of the iconic species Drosophila melanogaster to Sophophora melanogaster would require that the current and all previous type designations of the genus Drosophila are set aside by the International Commission on Zoological Nomenclature in accordance with article 78 of the International Code of Zoological Nomenclature after which Drosophila melanogaster can be assigned as the new type species. Since the alternatives are to rename either 1,200 species or the most famous organism in science, no action has been taken to resolve the paraphyly.

Drosophila species genome project

Drosophila are extensively used as a model organism in genetics, cell-biology, biochemistry, and especially developmental biology. Therefore, extensive efforts are made to sequence drosphilid genomes. The genomes of the following species have been fully or partially sequenced so far: The data will be used for many purposes, including evolutionary genome comparisons. D. simulans and D. sechellia are sister species, and provide viable offspring when crossed, while D. melanogaster and D. simulans produce infertile hybrid offspring. The Drosophila genome is often compared with the genomes of more distantly related species such as the honeybee Apis mellifera or the mosquito Anopheles gambiae.

Trivia

Several of the subgeneric and generic names are based on anagrams of Drosophila. These include:

External links

References

  1. Sturtevant, Alfred. The North American Species of Drosophila. The Carnegie Institute of Washington, 1921.
  2. [TaxoDros: The database on Taxonomy of Drosophilidae.]
  3. Markow, Theresa A., and O'Grady, Patrick M. 2006. Drosophila: A Guide to Species Identification and Use. 250pp. Elsevier Academic Press, London
Major Model Organisms in Genetic Studies
Lambda phage | E. coli | Chlamydomonas | Tetrahymena | Budding yeast | Fission yeast | Neurospora | Maize | Arabidopsis | C. elegans | Drosophila | Zebrafish | Rat | Mouse

 

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