Drosophila

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Many tractable animals serve as models for researching genetic systems in order to comprehend the molecular pathways that underpin numerous biological activities. Let us discuss our main question: what is drosophila? Drosophila meaning: Drosophila is a genus of flies in the Drosophilidae family, whose individuals are sometimes referred to as "little fruit flies," "pomace flies," "vinegar flies," or "wine flies" due to their proclivity for lingering around overripe or rotting fruit. They should not be confused with the Tephritidae, a related family of fruit flies (sometimes known as "real fruit flies"); tephritidae feed predominantly on unripe or ripe fruit, and many species, particularly the Mediterranean fruit fly, are considered agricultural pests.

Drosophila melanogaster, in particular, has been extensively utilised in genetics research and is a frequent model organism in developmental biology. In modern biological literature, the names "fruit fly" and "Drosophila" are frequently used interchangeably with D. melanogaster. The entire genus, on the other hand, has about 1,500 species with a wide range of appearances, behaviours, and breeding habitats.

Morphology 

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The majority of Drosophila species are small, measuring between 2 and 4 mm in length, however others are larger than a house fly. They have transverse black rings across the abdomen and brick red eyes and are normally pale yellow to reddish brown or black. Many species feature distinctive black patterns on their wings, as well as plumose (feathery) and arista antennae, as well as bristling on the head and thorax. The family is diagnosed based on the characteristics of wing venations. Saccades movement is a Drosophila flight path that consists of straight sequencing with quick and jerky spins of the wings interspersed between rest positions. It can, however, be rotated at a 90° angle in roughly 50 milliseconds when in saccadic movement. 

Drosophila wings may also beat at a rate of 220 times per second. Compound eye is one of the most complex varieties of eye found in insects, and it is found in Drosophila. Its unit component is the ommatidia; however, each ommatidium contains 760 ommatidia, as well as a cornea, eight photoreceptor cells (R1–8), numerous pigment cells, and some support cells.

Excess blue light is absorbed by reddish pigment cells in wild type Drosophila, hence ambient light does not make the fly blind. The rhabdomere and the cell body are the two most important elements of photoreceptor cells. The nucleus, on the other hand, is an active portion of the cell body, whereas the rhabdomere is 100m long and made up of toothbrush-like lumps of membrane called microvilli.

Furthermore, each microvillus is around 12–12 m in length and 60 nm in diameter. Furthermore, the vision protein rhodopsin is wrapped in the rhabdomere's membrane in the amount of 100 million molecules. As a result, rhodopsin's role is light absorption. On the other hand, rhabdomeres include a large number of additional visual proteins that are tightly bound in the gaps between microvilli, leaving very little room for cytoplasm.

Many proteins expressed in rhodopsin isoforms are present in photoreceptor cells in Drosophila. For example, blue light (480 nm) is absorbed by rhodopsin1 (Rh1), which is present in the R1–R6 photoreceptor cells. UV light (345 and 375 nm) is absorbed by photoreceptor cells that express a mixture of Rh3 and Rh4, which are found in the R7 and R8 photoreceptor cells. Blue (437 nm) and green (508 nm) light are similarly absorbed by Rh5 and Rh6, respectively. More than likely, each photoreceptor cell contains a protein called opsin, which is covalently coupled to a carotenoid chromophore called 11cis3hydroxyretinal. Each rhodopsin molecule contains this protein.

Habitat of Drosophila

Drosophila species can be found all over the world, with the tropical regions having the most species. Drosophila spread throughout the Hawaiian Islands, resulting in approximately 800 species. Deserts, tropical rainforests, towns, wetlands, and alpine zones are all places where they can be found. Some creatures in the north hibernate. 

The best cold-adapted species is D. montana, which is found primarily at high altitudes. Fruit, bark, slime fluxes, blooms, and mushrooms are all examples of decaying plant and fungus material where most species breed. At least one species, D. suzukii, has larvae that can feed on fresh fruit and can be a problem. Several creatures have evolved into parasites or predators. Many species are drawn to baits made of fermenting bananas or mushrooms, whereas others are not. Males may form leks, performing courtship in an area apart from breeding grounds, or concentrate around patches of ideal breeding substrate to compete for females.

Drosophila species such as Drosophila melanogaster, Drosophila immigrans, and Drosophila simulans are sometimes referred to as domestic species since they are closely related with humans. Human activities such as fruit shipments have mistakenly introduced these and other species (D. subobscura, Zaprionus indianus) all over the planet.

Reproduction in Drosophila

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Males in this genus have the longest sperm cells of any documented organism on Earth, with one species, Drosophila bifurca, having sperm cells measuring 58 mm (2.3 in). The cells are largely tail cells that are carried in tangled coils to the females. Other Drosophila species produce a small number of large sperm cells, with Drosophila bifurca producing the longest. Sperm cells from D. melanogaster are just 1.8 mm long, however they are still 35 times longer than human sperm. Several species of D. melanogaster have been observed to mate through traumatic insemination.

The reproductive potential of Drosophila species varies greatly. Those that breed in vast, relatively scarce resources, such fly D. melanogaster, have ovaries that mature 10–20 eggs at a time, allowing them to be laid all at once. Others may only lay one egg each day if they breed in more abundant but less nutritious substrates, such as leaves. Near the front end of the egg, one or more respiratory filaments extend above the surface, allowing oxygen to reach the embryo. Larvae eat the yeasts and bacteria that live on the decomposing breeding substrate, rather than the vegetable matter itself. Temperature, breeding substrate, and crowding all affect development time, which can range from 7 to more than 60 days depending on the species and environmental conditions.

Fruit flies lay eggs in response to changes in the environment. Eggs laid at a period (such as night) when the chances of survival are higher than eggs laid at other times (such as day) produce more larvae than eggs laid at those times. Regardless of the circumstances, laying eggs during this 'advantageous' time would result in more surviving kids and grandchildren than laying eggs at other times. Because this behaviour provides a significant reproductive advantage, D. melanogaster would adjust to environmental cycles as a result of this differential reproductive success.

Stimulus Responsible for Reproduction

Male Drosophila courtship behaviour is a desirable trait. Females react based on their interpretation of the male's behaviour. Drosophila males and females use a number of sensory cues to initiate and assess a possible mate's courtship readiness. Positioning, pheromone excretion, following females, tapping sounds with legs, singing, wing spreading, producing wing vibrations, genitalia licking, stomach bending, attempting to copulate, and the copulatory act itself are all examples of cues. Drosophila melanogaster and Drosophila simulans songs have been extensively researched. The sinusoidal nature of these enticing melodies varies across and within species.

The courtship behaviour of Drosophila melanogaster was also examined for sex-related genes, which have been linked to both male and female courtship behaviour. Recent studies have looked into the role of the fruitless (fru) and doublesex (dsx) genes, which are linked to sex behaviour.

In Drosophila, the fruitless (fru) gene aids in the regulation of the network for male courtship behaviour; when this gene is mutated, altered same-sex sexual behaviour in males is found. In contrast to traditional courtship, which is aimed towards females, male Drosophila with the fru mutation direct their wooing towards other males. When the fru mutation is lost, the regular courting behaviour returns.

Polyandry

Drosophila serrata, Drosophila pseudoobscura, Drosophila melanogaster, and Drosophila neo testacea are the Drosophila species used in the following section. In Drosophila, polyandry is a common mating arrangement. Female Drosophila have found that mating with several sex partners is a beneficial mating strategy. Pre and post copulatory mating are both beneficial. Pre-copulatory strategies are the behaviours connected with partner choice as well as the genetic contributions, such as gamete production, that both male and female Drosophila exhibit when it comes to mate choosing. Sperm competition, mating frequency, and sex-ratio meiotic drive are all post copulatory behaviours.

These are not all-inclusive lists. The number of mating partners in polyandry in Drosophila pseudoobscura in North America varies. There's a link between the number of times females choose to mate and third-chromosome chromosomal variations. The existence of the inverted polymorphism is thought to be the reason for female re-mating. The sex-ratio meiotic urge may be linked to the stability of these polymorphisms. The major mating mechanism for Drosophila subobscura, however, is monandry, which is unusual in Drosophila.

The Drosophila species Drosophila melanogaster, Drosophila simulans, and Drosophila mauritiana are used in the following section. Polyandrous Drosophila females compete for sperm in order to improve the fitness of their offspring. The female Drosophila possesses two sperm storage organs, allowing her to select the sperm that will inseminate her eggs. When it comes to mysterious female choices, females have very little power. 

Drosophila females use cryptic choice, one of numerous post-copulatory mechanisms that allows for the detection and ejection of sperm, reducing the possibility of inbreeding. Manier is a scientist that divided Drosophila melanogaster, Drosophila simulans, and Drosophila mauritiana post copulatory sexual selection into three stages: insemination, sperm storage, and fertilizable sperm. There are variances among the preceding species at each stage that play a role in the natural selection process.

Laboratory Cultured Drosophila

D. melanogaster is a common experimental animal because it can be cultivated in large numbers from the wild, has a quick generation time, and mutant animals are widely available. Thomas Hunt Morgan began working on D. melanogaster in 1906, and in 1910, he announced his first discovery of a white-eyed mutant to the scientific community. He needed a model organism to investigate genetic inheritance, thus he needed a species that could randomly acquire genetic mutations that manifested as physical alterations in adult animals. For finding chromosomes as the vector of gene inheritance in Drosophila, he won the Nobel Prize in Medicine in 1933. This and other Drosophila species are commonly utilised in genetics, embryogenesis, chronobiology, speciation, neuroscience, and other research fields.

However, some Drosophila species are difficult to culture in the laboratory, owing to the fact that they generally reproduce on a single host in the wild. It can be done for some with specific recipes for rearing media or by injecting substances found in the natural host, like as sterols; for others, it is (so far) impossible. In other circumstances, the larvae can develop on standard Drosophila lab media, but the female will not lay eggs; in these cases, placing in a little portion of the natural host to accept the eggs is often all that is required.

Use in Genetic Research

As in drosophila meaning, we discussed that these organisms are used in genetic testing, let us discuss these uses in detail:

Drosophila is regarded as one of the most reliable genetic model organisms, having advanced genetic research unlike any other. Because the human and fruit fly genes are so closely related, Drosophila is an excellent target for genetic research. Disease-causing genes in humans can be connected to those in fruit flies since their genes are so similar. On its four chromosomes, the fly has roughly 15,500 genes, whereas humans have about 22,000 genes spread over their 23 chromosomes. 

Drosophila's genome has a higher density of genes per chromosome than the human genome. Drosophila species are easy to research since they have a small and manageable number of chromosomes. These fly, like their human counterparts, carry genetic information and pass features down through generations. The features can then be investigated in different Drosophila lineages, with the results being used to deduce human genetic patterns. Drosophila research has aided in determining the fundamental rules for gene transfer in a variety of organisms. Drosophila is a good in vivo model for Alzheimer's disease research. Rhomboid proteases were first discovered in Drosophila, but they were quickly discovered to be highly conserved in eukaryotes, mitochondria, and bacteria.

Biome of Drosophila

Drosophila, like other animals, has a variety of microorganisms in its gut. Drosophila fitness and life cycle features appear to be influenced by the microbiota or microbiome of the fly gut. The microbiota in the gut of Drosophila is a hot topic in science right now.

Wolbachia and Spiroplasma are vertically transmitted endosymbionts found in Drosophila species. These endosymbionts can serve as reproductive manipulators, such as Wolbachia-induced cytoplasmic incompatibility or Spiroplasma poulsonii-induced male-killing in D. melanogaster. In 2018, the male-killing factor of the D. melanogaster strain was uncovered, putting an end to a decades-long mystery of why males die. This is the first bacterial factor to have a sex-specific effect on eukaryotic cells, as well as the first mechanism for male-killing phenotypes. 

They may, on the other hand, defend their hosts from infection. Drosophila Wolbachia can reduce viral loads when infected, and it's being investigated as a way to treat viral infections (like Dengue fever) by transferring Wolbachia to disease-vector mosquitoes. The Drosophila neotestacea strain S. poulsonii protects its host from parasitic wasps and nematodes by producing toxins that target the parasites rather than the host.

Systematics

The genus Drosophila, as it is now defined, is paraphyletic (see below) and has 1,450 recognised species, with many more thought to exist. The majority of the species belong to two subgenera: Drosophila (about 1,100 species) and Sophophora (approximately 330 species, including Drosophila (S.) melanogaster).

Idiomyia, a different genus or subgenus of Drosophila, is sometimes acknowledged as a separate genus or subgenus of Drosophila (estimated to have more than 500 species, with around 380 species reported), although this is not universally accepted. The genus Scaptomyza, which developed from the Hawaiian Drosophila and later recolonized continental areas, contains about 250 species.

Did You Know That

• The Cornell University Drosophila Species Stock Center in Ithaca, New York, maintains cultures of hundreds of species for researchers.

• Their lifespan is 35–45 days on average.