| Drosophila | |
|---|---|
 | |
| Drosophila pseudoobscura | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Family: | Drosophilidae |
| Subfamily: | Drosophilinae |
| Genus: | Drosophila Fallén, 1823 |
| Type species | |
| Musca funebris Fabricius, 1787 | |
| Subgenera | |
| Synonyms | |
OinopotaKirby & Spence, 1815 | |
Drosophila (/drəˈsɒfɪlə,drɒ-,droʊ-/[1][2]), fromAncient Greek δρόσος (drósos), meaning "dew", and φίλος (phílos), meaning "loving", is agenus offly, belonging to thefamilyDrosophilidae, whose members are often called "small fruit flies" or pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit. They should not be confused with theTephritidae, a related family, which are also called fruit flies (sometimes referred to as "true fruit flies"); tephritids feed primarily on unripe or ripefruit, with many species being regarded as destructive agricultural pests, especially theMediterranean fruit fly.
One species ofDrosophila in particular,Drosophila melanogaster, has been heavily used in research ingenetics and is a commonmodel organism indevelopmental biology. The terms "fruit fly" and "Drosophila" are often used synonymously withD. melanogaster in modern biological literature. The entire genus, however, contains more than 1,500 species[3] and is very diverse in appearance, behavior, and breeding habitat.
The term "Drosophila", meaning "dew-loving", is a modern scientificLatin adaptation fromGreek wordsδρόσος,drósos, "dew", andφίλος,phílos, "loving".
Drosophila species are small flies, typically pale yellow to reddish brown to black, with red eyes. When the eyes (essentially a film of lenses) are removed, the brain is revealed.Drosophila brain structure and function develop and age significantly fromlarval to adult stage. Developing brain structures make these flies a prime candidate for neuro-genetic research.[4] According to a study published inNature in October 2024, by the scientists examining the brain of an adult female Drosophila, the shape and location of each of its 130,000neurons and 50 millionsynapses were identified. In this study, the most detailed analysis ever conducted on the brain of an adult animal is represented.[5][6] 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 millimetres (0.079–0.157 in) long, but some, especially many of the Hawaiian species, are larger than ahouse fly.
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Environmental challenge by natural toxins helped to prepareDrosophilae todetoxDDT,[7]: Abstract [7]: 1365 [7]: 1369 by shaping theglutathioneS-transferase mechanism[7]: 1365 [7]: 1369 that metabolizes both.[7]: Abstract [8]
TheDrosophila genome is subject to a high degree of selection, especially unusually widespreadnegative selection compared to othertaxa. A majority of the genome is under selection of some sort, and a supermajority of this is occurring innon-coding DNA.[9]
Effective population size has been credibly suggested to positively correlate with the effect size of both negative andpositive selection.Recombination is likely to be a significant source ofdiversity. There is evidence thatcrossover is positively correlated withpolymorphism inDrosophila populations.[9]
Drosophila species are found all around the world, with more species in the tropical regions.Drosophila made their way to the Hawaiian Islands andradiated into over 800 species.[10] They can be found indeserts,tropical rainforest,cities,swamps, andalpine zones. Some northern specieshibernate. The northern speciesD. montana is the best cold-adapted,[11] and is primarily found at high latitudes or high altitudes.[12] Most species breed in various kinds of decaying plant andfungal material, includingfruit,bark,slime fluxes,flowers, andmushrooms.Drosophila species that are fruit-breeding are attracted to various products of fermentation, especiallyethanol andmethanol. Fruits exploited byDrosophila species include those with a high pectin concentration, which is an indicator of how much alcohol will be produced during fermentation. Citrus,morinda, apples, pears, plums, and apricots belong into this category.[13]
The larvae of at least one species,D. suzukii, can also feed in fresh fruit and can sometimes be a pest.[14] A few species have switched to beingparasites orpredators. Many species can be attracted to baits of fermentedbananas 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 formleks, conducting courtship in an area separate from breeding sites.[citation needed]
SeveralDrosophila species, includingD. melanogaster,D. immigrans, andD. simulans, are closely associated with humans, and are often referred to asdomestic species. These and other species (D. subobscura, and from a related genusZaprionus indianus[15][16][17]) have been accidentally introduced around the world by human activities such as fruit transports.
Males of this genus are known to have the longestsperm cells of any studied organism on Earth, including one species,D. bifurca, that has sperm cells that are 58 mm (2.3 in) long.[18] The cells mostly consist of a long, thread-like tail, and are delivered to the females in tangled coils. The other members of the genusDrosophila also make relatively few giant sperm cells, with that ofD. bifurca being the longest.[19]D. melanogaster sperm cells are a more modest 1.8 mm long, although this is still about 35 times longer than a human sperm. Several species in theD. melanogaster species group are known to mate bytraumatic insemination.[20]
Drosophila species vary widely in their reproductive capacity. Those such asD. melanogaster that breed in large, relatively rare resources haveovaries 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 theyeasts andmicroorganisms 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 astemperature, breeding substrate, and crowding.
Fruit flies lay eggs in response to environmental cycles. Eggs laid at a time (e.g., night) during which likelihood of survival is greater than in eggs laid at other times (e.g., day) yield more larvae than eggs that were laid at those times.Ceteris paribus, the habit of laying eggs at this 'advantageous' time would yield more surviving offspring, and more grandchildren, than the habit of laying eggs during other times. This differential reproductive success would causeD. melanogaster to adapt to environmental cycles, because this behavior has a major reproductive advantage.[21]
Their median lifespan is 35–45 days.[22]
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DNA damage accumulates inDrosophila intestinalstem cells with age.[23] Deficiencies in theDrosophila DNA damage response, including deficiencies in expression of genes involved inDNA damage repair, accelerates intestinal stem cell (enterocyte) aging.[24] Sharpless and Depinho[25] reviewed evidence that stem cells undergo intrinsic aging and speculated that stem cells grow old, in part, as a result of DNA damage.
The following is based onD. simulans andD. melanogaster.
Courtship behavior of maleDrosophila is an attractive behaviour.[26] Females respond via their perception of the behavior portrayed by the male.[27] Male and femaleDrosophila use a variety of sensory cues to initiate and assess courtship readiness of a potential mate.[26][27][28] The cues include the following behaviours: positioning, pheromone secretion, following females, making tapping sounds with legs, singing, wing spreading, creating wing vibrations, genitalia licking, bending the stomach, attempt to copulate, and the copulatory act itself.[29][26][27][28] The songs ofD. melanogaster andD. simulans have been studied extensively. These luring songs are sinusoidal in nature and vary within and between species.[28]
The courtship behavior ofDr. melanogaster has also been assessed for sex-related genes, which have been implicated in courtship behavior in both the male and female.[26] Recent experiments explore the role of fruitless (fru) and doublesex (dsx), a group of sex-behaviour linked genes.[30][26]
Thefruitless (fru) gene inDrosophila helps regulate the network for male courtship behavior; when a mutation to this gene occurs altered same sex sexual behavior in males is observed.[31] MaleDrosophila with thefru mutation direct their courtship towards other males as opposed to typical courtship, which would be directed towards females.[32] Loss of thefru mutation leads back to the typical courtship behavior.[32]
A novel class ofpheromones was found to be conserved across the subgenusDrosophila in 11 desert dwelling species.[33] These pheromones are triacylglycerides that are secreted exclusively by males from their ejaculatory bulb and transferred to females during mating. The function of the pheromones is to make the females unattractive to subsequent suitors and thus inhibit courtship by other males.
The following section is based on the followingDrosophila species:D. serrata,D. pseudoobscura,D. melanogaster, andD. neotestacea.Polyandry is a prominent mating system amongDrosophila.[34][35][36][37] Females mating with multiple sex partners has been a beneficial mating strategy forDrosophila.[34][35][36][37] The benefits include both pre and post copulatory mating. Pre-copulatory strategies are the behaviours associated withmate choice and the genetic contributions, such as production of gametes, that are exhibited by both male and femaleDrosophila regarding mate choice.[34][35] Post copulatory strategies include sperm competition, mating frequency, and sex-ratio meiotic drive.[34][35][36][37]
These lists are not inclusive. Polyandry among theD. pseudoobscura in North America vary in their number of mating partners.[36] There is a connection between the number of time females choose to mate and chromosomal variants of the third chromosome.[36] It is believed that the presence of the invertedpolymorphism is why re-mating by females occurs.[36] The stability of these polymorphisms may be related to the sex-ratio meiotic drive.[37]
However, forD. subobscura, the main mating system is monandry, not normally seen inDrosophila.[38]
The following section is based on the followingDrosophila species:D. melanogaster,D. simulans, andD. mauritiana.Sperm competition is a process that polyandrousDrosophila females use to increase the fitness of their offspring.[39][40][41][42][43] The femaleDrosophila has two sperm storage organs, the spermathecae and seminal receptacle, that allows her to choose the sperm that will be used to inseminate her eggs.[43] However, some species ofDrosophila have evolved to only use one or the other.[44] Females have little control when it comes tocryptic female choice.[42][40] FemaleDrosophila through cryptic choice, one of several post-copulatory mechanisms, which allows for the detection and expelling of sperm that reduces inbreeding possibilities.[41][40] Manieret al. (2013) has categorized the post copulatory sexual selection ofD. melanogaster,D. simulans, andD. mauritiana into the following three stages: insemination, sperm storage, and fertilizable sperm.[42] Among the preceding species there are variations at each stage that play a role in the natural selection process.[42] This sperm competition has been found to be a driving force in the establishment of reproductive isolation during speciation.[45][46]
Parthenogenesis does not occur inD. melanogaster, but in thegyn-f9 mutant,gynogenesis occurs at low frequency. The natural populations ofD. mangebeirai are entirely female, making it the only obligate parthenogenetic species of Drosophila. Parthenogenesis is facultative inparthenogenetica andmercatorum.[47][48]
D. melanogaster is a popular experimental animal because it is easily cultured en masse out of the wild, has a short generation time, and mutant animals are readily obtainable. In 1906,Thomas Hunt Morgan began his work onD. melanogaster and reported his first finding of awhite eyed mutant in 1910 to the academic community. He was in search of a model organism to study genetic heredity and required a species that could randomly acquire genetic mutation that would visibly manifest as morphological changes in the adult animal. His work onDrosophila earned him the 1933Nobel Prize in Medicine for identifyingchromosomes as the vector of inheritance for genes. This and otherDrosophila species are widely used in studies ofgenetics,embryogenesis,chronobiology,speciation,neurobiology, and other areas.[citation needed]
However, some species ofDrosophila are difficult to culture in the laboratory, often because they breed on a single specific host in the wild. For some, it can be done with particular recipes for rearing media, or by introducing chemicals such assterols that are found in the natural host; for others, it is (so far) impossible. In some cases, the larvae can develop on normalDrosophila 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.[49]
TheDrosophila Species Stock Center located atCornell University inIthaca, New York, maintains cultures of hundreds of species for researchers.[50]
Drosophila is considered one of the most valuable genetic model organisms; both adults and embryos are used in experiments.[51]Drosophila is a prime candidate for genetic research because the relationship between human and fruit fly genes is very close; disease-producing genes in humans can be linked to those inDrosophila.[52] The fly has approximately 15,500 genes on its four chromosomes, whereas humans have about 22,000 genes among their 23 chromosomes.[53] The low number of chromosomes makeDrosophila easier to study. Genetic traits can be studied through differentDrosophila lineages, and the findings can be applied to deduce genetic trends in humans. Research conducted onDrosophila has helped to determine the ground rules for genetic inheritance in many organisms.[54][4]
Drosophila is a useful in vivo tool to analyze Alzheimer's disease.[55]Rhomboid proteases were first detected inDrosophila but then found to behighly conserved acrosseukaryotes,mitochondria, andbacteria.[56][57] Melanin's ability to protect DNA againstionizing radiation has been most extensively demonstrated inDrosophila, including in the formative study by Hopwood et al. in 1985.[58]
Like other animals,Drosophila is associated with various bacteria in its gut. The fly gut microbiota or microbiome seems to have a central influence onDrosophila fitness and life history characteristics. Themicrobiota in the gut ofDrosophila represents an active current research field.
Drosophila species also harbour vertically transmitted endosymbionts, such asWolbachia andSpiroplasma. These endosymbionts can act as reproductive manipulators, such ascytoplasmic incompatibility induced byWolbachia or male-killing induced by theD. melanogaster Spiroplasma poulsonii (named MSRO). The male-killing factor of theD. melanogaster MSRO strain was discovered in 2018, solving a decades-old mystery of the cause of male-killing. This represents the first bacterial factor that affects eukaryotic cells in a sex-specific fashion, and is the first mechanism identified for male-killing phenotypes.[59] Alternatively, they may protect theirs hosts from infection.Drosophila Wolbachia can reduce viral loads upon infection, and is explored as a mechanism of controlling viral diseases (e.g. Dengue fever) by transferring theseWolbachia to disease-vector mosquitoes.[60] TheS. poulsonii strain ofDrosophila neotestacea protects its host from parasitic wasps and nematodes using toxins that preferentially attack the parasites instead of the host.[61][62][63]
Since theDrosophila species is one of the most used model organisms, it was vastly used in genetics. However, the effectabiotic factors,[64] such as temperature, has on themicrobiome onDrosophila species has recently been of great interest. Certain variations in temperature have an impact on the microbiome. It was observed that higher temperatures (31 °C) lead to an increase ofAcetobacter populations in thegut microbiome ofD. melanogaster as compared to lower temperatures (13 °C). In low temperatures (13 °C), the flies were more cold resistant and also had the highest concentration ofWolbachia.[65]
The microbiome in the gut can also be transplanted among organisms. It was found thatD. melanogaster became more cold-tolerant when the gut microbiota fromD. melanogaster that were reared at low temperatures. This depicted that the gut microbiome is correlated to physiological processes.[66]
Moreover, the microbiome plays a role in aggression, immunity, egg-laying preferences, locomotion andmetabolism. As for aggression, it plays a role to a certain degree during courtship. It was observed that germ-free flies were not as competitive compared to the wild-type males. Microbiome of theDrosophila species is also known to promote aggression by octopamine OA signalling. The microbiome has been shown to impact these fruit flies' social interactions, specifically aggressive behaviour that is seen duringcourtship andmating.[67]
Drosophila species are prey for many generalist predators, such asrobber flies. InHawaii, the introduction ofyellowjackets from mainland United States has led to the decline of many of the larger species. The larvae are preyed on by other fly larvae,staphylinidbeetles, andants.[68]
Fruit flies use several fast-acting neurotransmitters, similar to those found in humans, which allow neurons to communicate and coordinate behavior. Acetylcholine, glutamate, gamma-aminobutyric acid (GABA), dopamine, serotonin, and histamine are all neurotransmitters that can be found in humans, butDrosophila also have another neurotransmitter,octopamine, the analog of norepinephrine. Acetylcholine is the primary excitatory neurotransmitter and GABA is the primary inhibitory neurotransmitter utilized in the drosophila central nervous system. InDrosophila, the effects of many neurotransmitters can vary depending on the receptors and signaling pathways involved, allowing them to act as excitatory or inhibitory signals under different contexts. This versatility enables complex neural processing and behavioral flexibility.
Glutamate can serve as an excitatory neurotransmitter, specifically at the neuromuscular junction in fruit flies. This differs from vertebrates, where acetylcholine is used at these junctions.
InDrosophila, histamine primarily functions as a neurotransmitter in the visual system. It is released by photoreceptor cells to transmit visual information from the eye to the brain, making it essential for vision.
As with many eukaryotes,Drosophila expressSNAREs, and as with several others the components of the SNARE complex are known to be somewhat substitutable: Although the loss ofSNAP-25 - a component of neuronal SNAREs - is lethal,SNAP-24 can fully replace it. For another example, anR-SNARE not normally found insynapses can substitute forsynaptobrevin.[69]
TheSpätzle protein is aligand ofToll.[70][71] In addition tomelanin's more commonly known roles in theendoskeleton and inneurochemistry, melanization is one step in the immune responses to some pathogens.[70][71] Dudzicet al. (2019) additionally find a large number of sharedserine protease messengers between Spätzle/Toll and melanization and a large amount ofcrosstalk between these pathways.[70][71]
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ThegenusDrosophila as currently defined isparaphyletic (see below) and contains 1,450 described species,[3][72] while the total number of species is estimated at thousands.[73] The majority of thespecies are members of two subgenera:Drosophila (about 1,100 species) andSophophora (includingD. (S.) melanogaster; around 330 species).
The Hawaiian species ofDrosophila (estimated to be more than 500, with roughly 380 species described) are sometimes recognized as a separate genus or subgenus,Idiomyia,[3][74] but this is not widely accepted. About 250 species are part of the genusScaptomyza, which arose from the HawaiianDrosophila and later recolonized continental areas.
Evidence fromphylogenetic studies suggests these genera arose from within the genusDrosophila:[75][76]
Several of the subgeneric and generic names are based on anagrams ofDrosophila, includingDorsilopha,Lordiphosa,Siphlodora,Phloridosa, andPsilodorha.
Drosophila species are extensively used as model organisms in genetics (including population genetics), cell biology, biochemistry, and especially developmental biology. Therefore, extensive efforts are made to sequence drosophilid genomes. The genomes of these species have been fully sequenced:[77]
The data have been used for many purposes, including evolutionary genome comparisons.D. simulans andD. sechellia are sister species, and provide viable offspring when crossed, whileD. melanogaster andD. simulans produce infertilehybrid offspring. TheDrosophila genome is often compared with the genomes of more distantly related species such as the honeybeeApis mellifera or the mosquitoAnopheles gambiae.
TheDrosophila modEncode project conducted extensive work to annotateDrosophila genomes, profile transcripts, histone modifications, transcription factors, regulatory networks, and other aspects ofDrosophila genetics, and make predictions about gene expression among others.[78]
FlyBase serves as a centralized database of curated genomic data onDrosophila.[79]
TheDrosophila 12 Genomes Consortium has presented ten new genomes and combines those with previously released genomes forD. melanogaster andD. pseudoobscura to analyse the evolutionary history and common genomic structure of the genus. This includes the discovery oftransposable elements (TEs) and illumination of their evolutionary history.[80] Bartoloméet al. (2009) find at least1⁄3 of the TEs inD. melanogaster,D. simulans andD. yakuba have been acquired byhorizontal transfer. They find an average rate of 0.035 horizontal transfer events per TE family per million years. Bartolomé also finds horizontal transfer of TEs follows other relatedness metrics, with transfer events betweenD. melanogaster andD. simulans being twice as common as either of them withD. yakuba.[80]
