Fruit Flies, Ethanol, Good Health & Biocontrol

March 19, 2012

SEXUAL DEPRIVATION INCREASES Ethanol Intake in Drosophilia” was the semi-tabloid headline in the American Association for the Advancement of Science (AAAS) journal Science (16 March 2012; v. 1355, p. 1351). No fools, the AAAS knows a scientific title readily translatable into good headlines and writerly fun; parental Internet filters be damned. I was particularly impressed by Scientific American Science Sushi blog writer Christie Wilcox’s entertainingly deft mix of science, human implications and fun stuff on fruit flies with quotes from lead scientist Gilat Shohat-Ophir.

You Tube has an entertaining mix of titles on the subject, such as: 1) Flies turn to drinking after sexual refusal; 2) Study: Rejected Male Flies Turn to Alcohol; 3) Scientists Find Fruit Flies Self Medicate With Booze; and from Emory University, 4) ‘Drunken’ fruit flies use alcohol as a drug. The underlying science has a certain fascination, as there are similar neural (molecular) pathways for rewards and addiction (and their interaction with social experiences) in the two species: neuropeptide F (NPF) in fruit flies and neuropeptide Y (NPY) in humans. “Flies exhibit complex addiction-like behaviors,” write Shohat Ophir and colleagues K.R. Kaun, A. Azanchi and U. Heberlein, including “a preference for consuming ethanol-containing food, even if made unpalatable.”

In primitive natural settings, ethanol from fermentation of overripe fruit functions as a cue or lure for humans, fruit flies and other animals to locate fruit crops. Indeed, there is evidence that fruit fly larvae “have evolved resistance to fermentation products” from millennia of eating “yeasts growing on rotting fruit.” But fruit flies are not immune to alcohol-related mortality; the dose of the poison (alcohol) determining whether it is medicinal.

“The high resistance of Drosophila melanogaster (fruit fly) may make it uniquely suited to exploit curative properties of alcohol,” wrote Emory University’s Neil Milan, Balint Kacsoh, and Todd Schlenke in an article titled “Alcohol Consumption as Self-Medication against Blood-Borne Parasites in the Fruit Fly” in Current Biology (2012). “Ethanol levels found in natural D. melanogaster habitats range up to 6% ethanol by volume in rotting fruits, and 11% in wine seepages found at wineries. Fly consumption of food with moderate levels of ethanol (i.e., less than 4% by volume) results in increased fitness, but consumption of higher ethanol concentrations (i.e., greater than 4%) causes increasing fly mortality.”

One of the hazards of life for fruit flies is parasitic wasps, which sting the flies and lay eggs hatching into parasitoid larvae living inside and eventually killing the fruit fly. From the fruit fly’s perspective, biological control by natural enemies is deleterious and best prevented or overcome. “We have shown here that ethanol provides novel benefits to flies by reducing wasp infection, by increasing infection survival, and by allowing for a behavioral immune response against wasps based on consumption of it in toxic amounts,” wrote Milan and his colleagues. “To our knowledge, these data are the first to show that alcohol consumption can have a protective effect against infectious disease and in particular against blood-borne parasites. Given that alcohols are relatively ubiquitous compounds consumed by a number of organisms, protective effects of alcohol consumption may extend beyond fruit flies. Although many studies in humans have documented decreased immune function in chronic consumers of alcohol, little attempt has been made to assay any beneficial effect of acute or moderate alcohol use on parasite mortality or overall host fitness following infection.”

Scientists and students with science projects have been rearing fruit flies for over a century, and unraveling many of the mysteries of biological life. Indeed, the common fruit fly, “Drosophila melanogaster is emerging as one of the most effective tools for analyzing the function of human disease genes, including those responsible for developmental and neurological disorders, cancer, cardiovascular disease, metabolic and storage diseases, and genes required for the function of the visual, auditory and immune systems,” wrote Ethan Bier of the University of California, San Diego, in Nature Reviews Genetics (v.6, Jan. 2005). Depending on the matching criteria, anywhere from 33% to “75% of all human disease genes have related sequences” in fruit flies. Thus, “D. melanogaster can serve as a complex multicellular assay system for analysing the function of a wide array of gene functions involved in human disease.”

Something to think about next time you see those tiny (1/8 inch; 3 mm) golden or brownish fruit flies flitting around your overripe bananas, vegetable-laden bins and garbage cans.

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Honey, Bees, Better Sleep & Memories

April 24, 2010

“A TEASPOON OR TWO of honey before bed insures a restorative sleep,” writes Reese Halter in his informative little book, The Incomparable Honeybee & The Economics of Pollination. “A human liver stores about eight hours of glycogen – an important brain food. If you eat supper at 7 pm, by about 3 am your brain releases a stress hormone called cortisol. Cortisol scavenges the body, melts muscle tissue and converts it into glycogen to feed the brain. When released, cortisol causes the heart to beat faster and raises glucose insulin levels in the blood. Elevated cortisol can lead to obesity, diabetes, coronary disease and autoimmune breakdown. A teaspoon of honey at night fuels the liver with glucose and fructose, which is absorbed slowly – thus providing a restful sleep and preventing the release of cortisol.”

Perhaps honey also helps bees with their sleep?

In the 27 March 2010 Philosophical Transactions B of the Royal Society, researchers Timothy C. Roth and Vladimir V. Pravosudov at the University of Nevada, Reno, and Niels C. Rattenborg at the Max Planck Institute in Germany “examine the ecological relevance of sleep” for “memory/learning and hypothermia/torpor to conserve energy.” Sleep, it seems, is still a somewhat mysterious function. However, sleep in honeybees and other animals lends itself to ecological and experimental study.

Honeybee sleep is not exactly the hottest research topic on the planet at the moment. But that may change as the links between honeybee sleep, pathogen spread, and diseases are further explored. At past Entomological Society of America (ESA) meetings, Barrett Klein, who is finishing his Ph.D. in Ecology, Evolution and Behavior at the University of Texas in Austin, has attracted more attention for his entertaining role in insect art symposia.

At the Biozentrum in Wurzburg, Germany, Klein used an infrared camera to measure temperature changes and map sleep patterns of Carniolan bees (Apis melifera carnica) as they aged and changed tasks over time. Young worker bees progress from cleaning hive cells to nursing to food storage to foraging as they age.

Older forager bees sleep mostly at night, outside of cells, close to the edge of the hive where it is coldest. Younger cell cleaning bees sleep day and night, mostly inside cells where it is warmest. Foraging honeybees are the caste most likely to bring pathogens back to the hive. Thus, sleeping at night in the cold near the edge of the hive away from the warm brood reduces the potential for pathogen spread to the rest of the hive.

In the journal Learning & Memory, researchers in Germany used a web camera to “address the question if sleep in bees, like in other animals, improves memory consolidation.” Indeed, the webcam revealed that sleep deprivation had some negative effects on honeybee memory. At the ESA, Edgar Hernandez of the University of Missouri in St Louis described some of the work with “clock genes” and “clock proteins” playing a role in determining when bumble bees sleep.

With honeybees in trouble due to colony collapse, bumble bees and native bees are getting more attention. Nancy Adamson of Virginia Tech reported to the ESA that the honeybee situation has become so worrisome that the Virginia State Legislature voted to support research “aiming to provide information to Virginia farmers interested in supporting a broad spectrum of pollinators on their crops.” This includes providing harborage and habitat for bumble bees and other native bees.

“North America boasts over 4,000 species of native bees, many of which could serve as crop pollinators,” said Ann Fraser of Michigan’s Kalamazoo College. Native bees and bumble bees can pollinate crops on cloudy days and in cooler weather when honeybees are less active. Indeed, New Jersey and Pennsylvania watermelons are pollinated by 46 native bee species. In New York pumpkin fields, more bumble bee visits means heavier pumpkins, said Cornell’s Derek Artz.

Native bees and bumble bees can also be part of urban renewal. According to Ohio State University’s Scott Prajzner, vacant land within the city centers of Akron and Cleveland now supports community gardens and urban farms. This has boosted populations of native squash bees (Peponapis sp) and long-horned bees (Melissodes sp).

Perhaps we will all sleep better and have a more sustainable food supply by getting back to the basics: Honeybees for honey production, and letting bumble bees and native bees handle more crop pollination.