Archive for the 'Dipterans (Flies)' Category

Is ‘the Drosophila‘ actually Drosophila?

This post was chosen as an Editor's Selection for ResearchBlogging.orgCelebrities commonly change their names on the path to stardom. Elton John began life as Reginald Kenneth Dwight, John Denver as Henry Deutschendorf, Jr, and Bela Lugosi as Be’la Ferenc Dezso Blasko. A name change can make someone more marketable in the fickle entertainment industry. However, once someone makes it big, their name usually stays the same (excepting P-Diddy and Prince, whose constant name changes became marketing strategies in themselves). A celebrity’s name becomes the branding that represents and sells their fame.

What about name changes for scientific celebrities? I’m not talking about people, but rather the components of nature that we observe around ourselves and adorn with nomenclature. There was (unnecessary) public uproar when Pluto was re-designated as a Kuiper Belt planetoid. Neil deGrasse Tyson even got hate mail from children when the American Museum of Natural History updated its displays accordingly. The change was the result of a non-unanimous scientific consensus attempting to better define the bodies of the solar system, but many people had become attached to the idea of PLANET Pluto and reacted negatively to the news.

Now a new conundrum is brewing within scientific circles as biologists try to decide what to do when the nomenclature describing a celebrity organism no longer jives with scientific observation. Nature News asks, ‘What’s in a name?’. Well, when the name is Drosophila melanogaster, there’s 100 years of glorious scientific discoveries in a name.

Photo by mr.checker

D. melanogaster, the common fruit fly, was a major workhorse behind the early 20th century genetic revolution. Researchers like Thomas Hunt Morgan harnessed the fly’s fast reproductive cycle and simple care requirements to elucidate the fundamentals of heredity. Since then, the powerful D. melanogaster model has exploded to become a principle contributer to research in genetics, neurology, development, biomechanics, and evolution. Found in almost any biology department around the world, this animal is of tremendous historical and contemporary importance to science; a true celebrity.

However, there is one slight problem; Drosophila melanogaster is probably not Drosophila melanogaster.

The issue here is the status of the genus, Drosophila. This genus, as it is currently recognized, contains 1,450 species of fruit flies. A genus, or any level of taxonomic organization, is supposed to be monophyletic, that is; composed only of species that are evolutionarily closer to one another than they are to the members of any other genus. However, with Drosophila, this has been shown through extensive molecular and morphological analysis not to be the case.

Fruit Fly supertree. Adapted from Van der Linde and Houle, 2008

Look at the phylogenetic tree to the left (for an overview of phylogenetics, read this post). Each node on the tree represents a group of species of the same genus. Notice, however, that the 1,450 species of the Drosophila genus are split up into six different clades, interspersed with other genera. This is called paraphyly, and it points out an error in the taxonomic nomenclature. All the species of a given genus should be grouped together, in a monophyletic relationship. Ultimately, this means that there is going to have to be some reorganization of the genus. Some members of Drosophila are going to be ousted and given new names.

The obvious solution to preserve the celebrated D. melanogaster species name would seem to be leaving its clade (marked with a red arrow) as genus Drosophila and renaming the others. However, there are two problems with this. First of all, restructuring the genus in the manner would push out, and require the renaming, of 1,100 species of fruit flies. Furthermore, the type species Drosophila funebris (marked with an orange arrow), the animal from which the Drosophila genus was originally described in 1787, lies in a different clade than D. melanogaster. A recent petition to re-designate the genus type species as D. melanogaster was voted down by the International Commission on Zoological Nomenclature.

As it looks at the moment, D. melanogaster is probably on its way to becoming Sophophora melanogaster. This has generated shock and disbelief from biologists; citing possible research impediments should the name change go through. In addition, they surely have a sentimental attachment to the name of their favorite laboratory arthropod. When biologists say ‘Drosophila‘, they mean Drosophila melanogaster. This celebrated animal has a strong claim to being the most important and powerful research tool biologists have in their arsenal. However, even D. melanogaster, like Pluto, may need to bend in name to the powers of parsimonious taxonomic nomenclature.
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Read more about the Drosophila name fight here and here at Nature News, or here at Catalogue of Organisms

Check out some of my other posts about phylogenetics:

References:

    Kim Van der Linde, & David Houle (2008). A supertree analysis and literature review of the genus Drosophila and closely related genera (Diptera, Drosophilidae)Insect Syst. Evol., 39, 241-267

Fruit fly sperm race

Check out this awesome video of fluorescent labeled fruit fly sperm racing through the reproductive tract of a female Drosophila melanogaster. The sperm from one male are labeled with a green marker and sperm from another male are labeled with a much fainter red marker. Read more about the high stakes world of sperm competition at Not Exactly Rocket Science, which recently moved to Discover Blogs.

This video is from recent research published in Science.

Arthropod Roundup: Callinectes in the UK, horny females, artificial arthropod hair, and genetic mosquito control

Brief blurbs about recent arthropod news and research:

  • The blue crab, Callinectes sapidus, has been found in England for the second time ever. These ill-tempered, but delicious, swimming crabs are native to North America; where they represent a major marine fishery despite serious conservation concerns. Previously, blue crabs have turned up in Japan and the Mediterranean. It is conventionally thought that these crabs were brought in as larvae in ship ballast water and have since gained a foothold in their new homes. It is possible that this blue crab in Cornwall also came over from America in ballast water, or it could have been carried on ocean currents up from the Mediterranean population. It is unclear weather this is an isolated individual or a representative of a new invasive population.
  • You will be disappointed to learn that the horny females I referred to in the title are dung beetles. One usually associates the growth of horns and antlers with males who use them to battle for dominance in a social hierarchy or for their pick of the choicest females. However, female dung beetles, Onthophagus sagittarius, are known to have much more impressive horns than their male counterparts. A new study suggests that these horns are used by the females to compete over reproductive resources (i.e. poop). Size matched females with larger horns were found to achieve greater reproductive fitness, making horn size a positively selected female secondary sex characteristic in these beetles. (Via 80Beats)

    Horned Onthophagus sagittarius females square off. Photo: Sean Stankowski

  • New research reports the development of synthetic superhydrophobic materials inspired by tiny, water repellent hairs in insects. These hairs are found on the legs of water walkers and the backs of Stenocarid beetles, which use the hairs to channel water droplets to their mouth.
  • The genomes of the malaria mosquito, Anopheles gambiae, and the yellow fever mosquito, Aedes aegypti, were published in 2002 and 2006, respectively. These sequencing efforts appear to be bearing a lot of fruit as of late; as several genetic approaches to controlling the spread of mosquito vectored diseases have been proposed. These include; increasing the immunity of mosquitoes to the dengue fever virus, weakening mosquitoes by preventing waste secretion, and preventing female mosquitoes from developing functioning flight structures. Some of these ideas are pretty far from real-world application unfortunately, and the buzz surrounding them seems to be the result of overly-excitable university PR departments.

Arthropod Roundup: Crabzilla, altruistic ants, and neuronal recordings from Drosophila in flight.

Quick notes about recent Arthropod news and research:

  • The National Sealife Centre in Birmingham, England is hosting a special guest, on loan from Japan. Meet ‘Crabzilla’, a not-quite full grown Japanese spider crab, Macrocheira kaempferi. Crabzilla has an impressive leg-span of about 10 ft, but members of this species can reach over 13 ft. By length, they are the largest know arthropods on the planet. You can read more about Crabzilla’s visit to the UK at the Daily Mail.
  • New research on the ant species, Temnothorax unifasciatus, found compelling evidence of altruistic behavior. Altruism is commonly observed in social insects, as single individuals often sacrifice their energies or lives for the good of the colonial super-organism. In the present study, the researchers showed that ants infected with a deadly and contagious fungus would often leave the colony and die in seclusion. This prevents transmission of the disease to other members of the closely interacting colony. Read more at the BBC.
  • Finally, researchers have developed new techniques for recording electrical signals from fruit fly neurons while the animals are in tethered flight. Fruit flies, Drosophila melanogaster are the go-to arthropod model organisms, and a plethora of molecular and physiological tools are available for studying any aspect of their biology. This new neuronal recording technique was applied to look at the activity of visual pathways in the brain during flight. The researchers found that the stimulus response time of the Drosophila visual system nearly doubles when the animal is in flight. This allows the flies to change direction rapidly mid-flight in order to avoid obstacles. This work was published in Nature Neuroscience. Read more at Science Daily.

    A tethered fruit fly in flight with a pink electrode in its brain. Photo by Gaby Maimon and Michael Dickinson.

Abandon Ship! Parasitoid fly larvae flee their doomed host

A new research article, published in the Proceedings of the Royal Society B discusses a unique insect endoparasitoid. This fly larva typically grows inside an aphid host until it matures and exits the aphid. However, the researchers have discovered that the larva is capable of abandoning its aphid early if the aphid is threatened by a predator. This behavior prevents the larva from going down with the ship.

The red Endaphis fugitiva larva parasitoid exiting its injured aphid host. Image adapted from Muratori et al., 2010.

Larval endoparasitism is well know among insects, with parasitoid wasps being the most common example. However, some flies also engage in endoparasitism. One such fly, Endaphis fugitiva, was describe just last year. Unlike parasitoid wasps, which inject their eggs into the body of their host insect, E. fugitiva lays its eggs on the leaves of plants with aphid infestations. The eggs hatch, and the fly larvae seek out the nearest aphid, where they use their specialized mouthparts to bore into the aphid’s abdomen. Once inside, the larva feeds off the aphid until it matures. It exits through the anus, killing the aphid, and drops to the ground. There, the larval fly forms a cocoon and metamorphosizes into an adult.

In the most recent paper, Muratori et al. have shown that the E. fugitiva larva can sense that its host is in danger and jump ship before it is consumed along with the aphid. They demonstrated that the fly larvae will exit the aphid if the aphid is injured or exposed to predation by lacewings or syrphid larva. Surprisingly, the researchers also found that early-ejecting fly larvae were still able to grow to full size and pupate into adults in the same amount of time as normal.

Muratori et al. hypothesize three possible mechanisms by which the larval fly may be able to sense its host’s imminent demise:

  • Emergency cues such as stress factors in the aphid’s haemolymph could be detected by the parasitoid larva.
  • Direct contact between the predators mouthparts and the parasitoid larva.
  • A drop in the internal pressure of the aphid as the predator begins to suck out its internal fluids could be detected by the parasitoid larva.

Watch this video of a larval fly fleeing from its host aphid as the aphid is attacked by a lacewing (Via Nature). What a way for the poor aphid to go. Just as a predator starts sucking out your internal fluids, a massive fly larva shreds your innards and bursts out your anus.

References:

Muratori, F.B., Borlee, S. & Messing, R.H., 2010. Induced niche shift as an anti-predator response for an endoparasitoid. Proc. R. Soc. B, published online before print January 13, 2010

Muratori, F.B., Gagne, R.J. & Messing, R.H., 2009. Ecological traits of a new aphid parasitoid, Endaphis fugitiva (Diptera: Cecidomyiidae), and its potential for biological control of the banana aphid Pentalonia nigronervosa (Hemiptera: Aphididae). Biological Control, 50(2), 185-193.


I have moved.
Arthropoda can now be found here.

Michael Bok is a graduate student studying the visual system of mantis shrimp.

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