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.


The Asian Invasion -Insects in Global Trade

January 8, 2011

NATURAL WOOD PRODUCTS are better than synthetic petrochemical plastics is a common refrain, almost a rallying cry for many who consider themselves “green,” organic, sustainable or environmentally correct. Thus, the fashionable zeal in some sectors of society to ban plastic shopping bags and allow wood-pulp paper bags. But what if being “green” and using natural materials like wood instead of synthetic petrochemical plastics led to deforestation and pestilence? That’s pretty much the world trade situation these days.

At first glance wood pallets, crates, dunnage, and packaging materials seem to be the low-cost, sustainable “green” alternative vis-a-vis more expensive, synthetic petrochemical plastics. But wood packing materials used in global trade have spread a pestilence of native Asian wood-boring beetles to new homes worldwide. The North American invasion by Asian wood-boring species of bark beetles, ambrosia beetles, and long-horned beetles were among the hot topics at the Entomological Society of America (ESA) annual meeting of Dec. 2010 in San Diego, California.

Since hitchhiking to North America from Asia in solid wood packing materials and being detected near Detroit, Michigan in 2002, the wood-boring emerald ash borer has killed an estimated 30 million ash trees in the northern United States and southern Canada. The remaining North American ash trees are threatened. Though Sara Tanis, whose Michigan State University work is on You Tube, reported at the ESA annual meeting that blue ash (Fraxinus quadrangulata) “can withstand infestation and continue to survive.”

Emerald ash borer control is now multinational, involving the U.S. states of Michigan, Illinois, Indiana, Iowa, Kentucky, Maryland, Minnesota, Missouri, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin plus the Canadian provinces of Ontario and Quebec. The Asian wood-boring beetle invasion is so far along it might make little difference if world trade abandoned wood pallets, crates, dunnage, and packing materials.

“Control strategies are now shifting to how we can manage established populations in the longer term,” Shajahan Johny of the Canadian Forest Service Great Lakes Forestry Centre in Sault Ste. Marie, Ontario, Canada, told the ESA. “One possibility is biological control, which is recognized as the most suitable long-term pest management strategy for invasive species.” Johny is looking at fungi in the genera Isaria and Paecilomyces attacking emerald ash borer in Ontario.

In Michigan and Ontario, Canada, the early emerald ash borer hot spots, woodpeckers can peck out up to half the wood-borers; which is good for the birds, but not stopping beetle movement to new trees. “In their native habitats, Agrilus (sci name of genus of 3,000 wood-boring beetles) populations are generally suppressed by a diverse group of natural enemies and/or host tree resistance, and rarely become serious pests,” said Jian Duan, Lead Scientist of the emerald ash borer biological control team at the USDA-ARS Beneficial Insects Introduction Research Unit in Newark, Delaware. The USDA has searched Russia, Mongolia, China, and South Korea to find specialized parasitoids that can be introduced to North America to hunt wood-boring beetle eggs concealed under loose bark and larvae hidden inside trees. The idea being to restore a natural ecological balance.

Asia has not been immune to wood-boring beetle outbreaks. “The mass mortality of oak trees (Japanese oak wilt) has recently increased explosively in Japan,” Masahiko Tokoro of the Forestry and Forest Products Research Institute (FFPRI) in Ibaraki, Japan, told the ESA. The Japanese are using a Decoy Tree Method (patent pending). Trap trees are baited with an aggregation pheromone attracting the wood-boring oak ambrosia beetle (Platypus quercivorus). Ethanol (alcohol) is added to the mix, because it is emitted by unhealthy or stressed trees and attracts beetles.

“Oak trees survive when they have been inoculated with a fungicide against the pathogenic fungus (oak wilt) before being attacked,” said Tokoro. “The decoy trees are lethal to the beetles because the symbiotic fungi (i.e. the ambrosia) that the beetles feed on are killed by the fungicide.” Neighboring trees can be similarly protected.

Variations on this method called push-pull are being developed in the U.S. to protect nursery trees from exotic ambrosia beetles (Xylosandrus spp.), said Christopher Ranger of the USDA-ARS Application Technology Research Unit in Wooster, Ohio. Ethanol is injected into sweetbay magnolia trap trees to stimulate ambrosia beetle attack. Beetles are “pushed” out of trees being protected by application of a repellent compound such as verbenone (dispensers) or via commercial botanical repellents such as Armorex, Veggie Pharm, Cinnacure. Azatin or Eco-Trol.