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.


Moth-Eye Reflections

September 8, 2011

“ANTI-REFLECTION MOTH-EYE ARRAYS are now widely applied in panels of instruments, like cellphones and in window panes,” wrote Doekele G. Stavenga of the Department of Neurobiophysics at the University of Groningen (The Netherlands) in Functional Surfaces in Biology -Little Structures With Big Effects, Volume 1. The editor, Stanislav Gorb of the University of Kiel (Germany), thanked senior publishing editor Zuzana Bernhart (Plant Pathology and Entomology; Springer, Holland) for her “belief in this topic and her personal help.” Bernhart said that a big dose of the inspiration for the two book volumes came from what have become regular symposia on insect-inspired innovations at the Entomological Society of America (ESA) annnual meetings.

At nanotechnology events, insects and entomology are acknowledged frequently as inspiration. For example, at the California NanoSystems Institute on UCLA’s campus, Tomohide Takami, a researcher visiting from the Division of Quantum Phases and Devices at Konkuk University (South Korea), said “we have fabricated a bio-mimetic probe called ‘nano-mosquito’…to explore nano-world.” In a prior lecture Xiaodong Chen visiting from Nanyang Technological University (Singapore) noted: 1) energy storage devices, lightweight aerospace materials, and self-assembly inspired by diatoms and honey bee honeycombs; 2) Singapore’s waterfront Esplanade Theatres on the Bay is an architectural shape perhaps inspired by fly eyes and tropical fruit (durian); 3) moth eyes that are anti-reflective (so enemies do not see the glint of their eyes) and provide better vision at night and in fogs inspire solar cells that harvest more light.

“Anti-reflective moth-eye arrays could produce up to 12% more energy than those employing single layer anti-reflective coatings,” via “a reduction of up to 70% of the light reflected from the surface,” said Stuart Boden and Darren Bagnall of the University of South Hampton (UK) in their poster display (“Bio-mimetic nanostructured surfaces for near zero reflection from sunrise to sunset”). Via electron beam lithography and dry etching (subwavelength): “We have fabricated a range of moth-eye arrays in silicon. Reflectance measurements confirm the low reflectivity of these arrays over the visible and near infra-red wavelengths, making them excellent candidates for reducing reflection on solar cells.”

“Insects have facetted, compound eyes, consisting of numerous anatomically identical units, the ommatidia,” wrote Doekele Stavenga and his colleagues in the Proceedings of the Royal Society B (22 March 2006. 273(1587):661-667), a journal whose roots date back over 200 years to London in 1800. Back in the 1960s, researchers discovered that the outer surfaces of moth eyes had “an array of cuticular protuberances termed corneal nipples” which reduce light reflection to 1%. Thus, moth night vision is improved by allowing 99% of light to enter moth eyes. Fewer reflections or less glint from the eyes makes moths harder for predators to detect. [Moth defenses against bat echo-location is another story, for another time]

“Moths thus realize a much higher light sensitivity than butterflies, allowing a nocturnal instead of diurnal (daylight) lifestyle,” wrote Stavenga et al. “A moth with large, glittering eyes will be quite conspicuous, and therefore its visibility is reduced by the eye reflectance decreasing… The insight that nipple arrays can strongly reduce surface reflectance has been widely technically applied, e.g. in window panes, cell phone displays and camera lenses.”

Moth-eye antireflection coatings (ARCs), “which are inspired by the grainy microstructures on the corneas of moths consisting of a non-close-packed hexagonal array of conical nipples, can suppress reflection over a broader range of wavelengths and wider angles of incidence than traditional multilayer dielectric ARCs,” wrote Chih-Hung Sun and other chemical engineering colleagues at the University of Florida, Gainesville, in an article titled “Large-scale assembly of periodic nanostructures with metastable square lattices.”

Moth-eye ARCs, reported Sun et al., “are widely utilized in eliminating the “ghost images” for flat-panel displays, increasing the transmittance for optical lenses, improving the out-coupling efficiency of semiconductor light emitting diodes, and enhancing the conversion efficiency of solar cells.”

“Since all biological structures are multifunctional, it makes them even more interesting,” wrote Stanislav Gorb in his introduction to the Springer book, Functional Surfaces in Biology. “Small surface structures at the micrometer and nanometer scales (i.e. very very small) are often vitally important for a particular function or a set of diverse functions…Because of the structural and chemical complexity of biological surfaces, exact working mechanisms have been clarified only for some systems.”

Some other possible innovations from the micro-world described in the Springer book: Protective slime coatings that protect seeds from rotting (e.g. pathogens) and stimulate or inhibit seed germination as needed. Water-repellent hairs have been “invented” by spiders. Water bugs can inspire waterproofing, anti-submersion fabrics, and surfaces promoting water runoff. Self-cleaning plant surfaces that cause water to form spheres and roll off are inspiration for water-repellent surfaces that might also trap air underwater for breathing. The plant world’s system of water transport pipes (xylem) can yield ideas for water transport systems. Feather microstructures could inspire aerodynamic innovations to complement lessons learned from insect flight.

We have barely scratched the surface of the ingenious natural world that we inhabit and share.

Asian Innovations in Insect Control

August 20, 2011

Innovations in Insect Control in Asia date back almost 2,000 years to when ancient Chinese farmers learned the art of biological insect control. China’s ancient orchardists annually introduced colonies of predatory ants to cultivated trees to control caterpillars and other pests of crops such as citrus. Ancient Chinese biocontrol practices included constructing bamboo bridges between trees, so predatory ants could easily wander from tree to tree foraging for pests.

Fast forward to the twenty-first century: Tea is arguably the second most widely consumed beverage, after water. Tea production occupies 2.7 million ha (6.7 million acres) in 34 countries, with 78% of production in Asia and 16% in Africa. Sustainable tea production practices emphasize displacing pesticides with cultural and biological control practices to control spider mites and other pests in tea plantations.

“The application of natural enemies in tea pest control aroused a large amount of investigations in the tea producing countries,” reported Yang Yajun and colleagues at the Tea Research Institute of Chinese Academy of Sciences at the 2005 International Symposium on Innovation in Tea Science and Sustainable Development in Tea Industry. “In South India, investigations showed the introduction of three species of entomophagous fungi in the control of tea spider mite (Oligonychus coffeae). In Japan, the use of pesticide-resistant predatory mite resulted in successful control…In Japan, one fungal preparation and one bacterial preparation were registered and used in control of tea diseases.” In China and Japan, viruses stop pesky leafrollers and loopers. Japan also has five fungal biocontrol products, one bacterial biocontrol preparation, and several kinds of parasitic and predatory natural enemy preparations to control tea insect pests.

“Great achievements in the application of physical and agricultural control methods in controlling the tea pests were advanced,” said Yajun et al. In Japan, China, and Malawi (Africa), yellow sticky traps and reflective films (near ultra-violet light) help control tea aphids, thrips, and leafhoppers (70-80% pest reduction). “A special mist wind insect-sucking machine was developed in Japan,” and it reduces tea leafhopper, whitefly, and spider mite populations.

Sex pheromones have been used for mating disruption in Japanese tea gardens since 1983 to control a pesky tea leafroller. Sex pheromones are also being used against other tea pests in Japan and China. Natural volatiles from the tea plant that attract natural enemies but not pests are also under development. For example, the April 2004 Chinese Journal of Applied Ecology (15(4):623-626) reported that beneficial lady beetles, green lacewings, and hover flys (syrphids) controlling tea aphids were attracted by natural compounds such as nerol from tea flowers, n-octanol from intact tea shoots, and geraniol, methyl salicylate, benzaldehyde, and hexanal from aphid-damaged tea shoots.

At Entomological Society of America (ESA) annual meetingss, California Department of Food and Agriculture (CDFA) officials report that T. Kanzawa’s 1939 translation of Professor Dr. Shonen Matsumura‘s 1931 book, 6000 Illustrated Insects of Japan-Empire, is still used to help with identification and control of invasive insect pests like the dusky-winged fruit fly (Drosophila suzukii). Oregon entomologist Jana Lee told the ESA that the Japanese get 100% fruit fly protection by placing 0.98 mm (0.04 inch) mesh over blueberries 20 days pre-harvest. After the harvest, 100% of fruit fly eggs and newly hatched larvae on cherries are killed by holding the fruit at 1.6-2.2 C (29-36 F). In Japanese experiments, fruit fly egg laying in cherries was reduced 30-60% with botanicals such as eucalyptus, neem, and tansy. In other promising Japanese research, Kotaro Konno and Hiroshi Ono told the ESA that latex from the same mulberry leaves used to safely grow silkworms since ancient times could be an effective botanical insecticide against other pests.

Since the 1920s, the USDA has been importing Japanese and Korean biocontrol organisms, like Tiphia wasps to control Oriental beetles and Japanese beetles attacking golf courses, turf, crops, and landscape ornamentals. Japan is currently patenting decoy tree technologies to help stop an explosive outbreak of oak wilt fungus (Raffaelea quercivora), caused by mass attacks of ambrosia beetles (Platypus quercivorus), said Masahiko Tokoro of the Forestry and Forest Products Research Institute (FFPRI) in Ibaraki, Japan (See earlier blog post: The Asian Invasion -Insects in Global Trade).

In South Korean greenhouse tests, Sangwon Kim and Un Taek Lim of Andong National University told the ESA of greenhouse tests showing the superiority of yellow circles against a black background versus conventional rectangular yellow sticky traps for capturing pesky whiteflies and thrips. “In laboratory behavioral studies using different backgrounds and shapes, yellow sticky card with black background was 1.8 times more attractive than sticky card without background, and triangle attracted 1.5 times more sweetpotato whitefly (Bemisia tabaci) than square,” said Kim. Black sticky cards with small yellow circles caught 180% more sweetpotato whitefly than cards with larger circles.

Natural vs Synthetic Repellents

March 30, 2010

SYNTHETIC OR NATURAL? Which is best? Since the 1950s the synthetic chemical DEET (N, N-diethyl-m-toluamide) has been the standard to which all other mosquito, tick and biting fly repellents have been compared. DEET is still the standard of comparison, but the long search for natural or organic repellents is finally yielding a number of potential alternatives, some from the plant world and others from such unlikely places as human sweat.

The progress in besting DEET has been so stunning that the Entomological Society of America (ESA) presented a four-hour symposium with a dozen 20-minute talks, Celebrating the Success of Global Insect Repellent Science Research. Habitues of the ESA know that in the world view of a female mosquito, humans are little more than scented apes put on Earth to be protein-rich blood meals to begat new generations of what we call vermin and they consider kin.

Sweat, heat, and carbon dioxide, that greenhouse gas that humans respire into the atmosphere with every exhaled breath, tip off mosquitoes and other bloodsuckers that the human food wagon has arrived. Actually, that’s putting it a bit crudely. Mosquitoes are actually connoisseurs, and sniff out humans like a gourmet would a fine wine. To be even more accurate, females are the true connoisseurs and gourmands, the bloodsucking vampire sex of the mosquito world. Male mosquitoes are true flower children, pacifists abhorring the bloodsucking life and mostly passing the time pollinating plants.

Longtime scholars of mosquito feeding habits on humans, like Willem Takken at Wageningen University in The Netherlands, have tallied 300 to 350 compounds mosquitoes can use to identify humans. About 60 of these odors are common to every person, and the rest give each human a slightly different scent. Thus, we oftentimes remember a person by their distinctive smell. Elegant experimental techniques like gene silencing and transferring mosquito olfactory genes to fruit flies allows the mapping of mosquito odor preferences. Some mosquito species, such as the malaria-vector Anopheles gambiae, can zero right in on humans. Other mosquito species may bypass humans in favor of cows, livestock or other animal species.

From a practical standpoint, if diseases like malaria, dengue and yellow fever are not a concern and you need protection for only an hour or two, one of the many commercial botanical repellents is likely to suffice as an alternative to DEET. Lemon eucalyptus products, including Quwenling from China, get high marks from the CDC. Daniel Strickman at the USDA-ARS in Beltsville, MD, and others have compiled long lists of botanicals good for about an hour of repellency, including: clove, geranium (geraniol), citronella, celery, lemon, lime, neem, pyrethrum, fringed rue, patchouli, pennyroyal, soybean, thyme, niaouli (Melaleuca viridiflora), makaen (Zanthoxylum limonella), Mexican tea (Chenopodium ambrosioides), Labrador tea (Ledum groenlandicum), and lily-of-the-valley.

However, natural or organic does not automatically mean safe or lacking in toxicity. Natural compounds, like synthetics, can also be sources of skin irritation, toxicity, and carcinogenicity. Even lemon eucalyptus oil can be an eye irritant. And as some herbal tea drinkers have learned the hard way (as is documented in the medical journals), the active ingredients in pennyroyal, violets and other botanicals can be dangerously toxic in too high a dose or with prolonged use.

The U.S. EPA can give what is known in legalese as FIFRA 25(b) Exemptions (Minimum Risk Pesticides), the USDA’s Strickland told the ESA repellent symposium. This allows some natural compound active ingredients to be used as repellents without testing. Examples include cedar oil (from eastern red cedar), citronella, garlic, geranium, lemongrass, peppermint, soybean oil and thyme. The International Fragrance Association investigates active ingredients to avoid lawsuits over cosmetics, though even this is not a guarantee against allergic reactions.

In short, caution is the watchword. Try a little bit first, and to be really safe use long sleeves and pants so that minimal repellent directly contacts the skin (as both natural and synthetic chemicals may penetrate the skin and enter the bloodstream).

Joel Coats’ lab at the University of Iowa provided the ESA symposium with a glimpse of the future. Coats’ lab is well-known in entomological circles for its pioneering work with naturally occurring monoterpene and sesquiterpene chemicals in plants such as catnip (Nepeta cataria), Osage orange (Maclura pomifera), West Indian sandalwood (Amyris balsamifera), and Siam-wood (Fokenia hodginsii). In short, the chemicals known as monoterpenes provide a broad spatial repellency, and the “oxygenated sesquiterpenes” provide contact repellency. And a mixture of the two provides both modes of action and the best repellency. You will probably want to wait for the testing to be completed and commercial products to be formulated.

But back to the question of which is best, natural or synthetic. Some of the best natural compounds, and there are too many to list, can outperform DEET. Even some new synthetics can outperform DEET in some ways. If you have a job that keeps you in the field and exposed to mosquitoes, biting flies and ticks for 12 or 24 hours at a time, then you need some heavy-duty, long-lasting protection. Indeed, that is the holy grail for organizations like the U.S. Army.

Life may have seemed simpler in the 1960s when Mr. Robinson told Dustin Hoffman in the movie The Graduate that the future was in plastics. Quantitative structure-activity relationships (QSAR) is the future in 2010, say Coats and his graduate student Gretchen Paluch. They forsee a leapfrogging future where natural repellents better than DEET lead to new synthetic spinoffs of nature’s best molecules better than anything yet known.

They believe that patchouli, cedar oil and other natural compounds can (via QSAR) provide the skeleton for designing new repellent molecules. However, it may not be so simple, as a fine ecological balance has evolved in nature. Though it may seem contradictory, even so-called repellent plants like catnip, which is famous for repellent molecules like neptalactone, also contain attractant molecules. Possibly the best repellents will also contain elements of attraction. But that is another story for another time.

Headless Zombie Fire Ants, Brain-Eating Flies!

January 15, 2010

FIRE ANTS ATTACKED by BRAIN-EATING FLY MAGGOTS, transformed into HEADLESS ZOMBIES. So says the ever-helpful Kavita Sharma, an Auburn University entomologist in fire ant-plagued Alabama, a likely port of disembarkation for the painfully-biting red imported fire ant invasion of the United States that began in earnest during World War II.

If you missed it on the evening news or failed to scan the supermarket tabloid headlines, the Internet tabloid journalists have had fun dramatizing it on You Tube. Not that the brain-eating flies have yet provided much relief from the ever-expanding, biting fire ant invasion raging from Texas, Oklahoma and New Mexico to Florida and the Carolinas. Indeed, the ants may be bent on global colonization, having expanded from their South America homeland in Argentina to North America, Australia and other continents.

Several decades of pesticide spraying, and more recently poison baits, have done little to slow the spread of the biting ants, which have effectively colonized the southern U.S. and seem to be adapting to slightly cooler northern climes. Not that it is all bad, if you can avoid being bitten. The ravenous ants provide vital biological pest control on some farms; for example ridding cotton farms of bollworms, weevils and other pests that would otherwise be sprayed with pesticides. No doubt, the ants would also make mincemeat and hash out of any bedbugs in an infested mattress placed in their path.

But the pain of the bites and the problematic fire ant mounds erupting in lawns and pastures necessitate control measures. As is typical of pest control programs, years of failed but costly chemical eradication eventually breed pesticide-resistant insects. Score one point for the fire ants and Darwin’s theory of evolution. Score good revenues for valiant pest control efforts. But longer term, insect genetics adapt to almost anything thrown at them.

In the 1954 sci-fi flick, Them, even Fess Parker (Davy Crockett fame), Leonard Nimoy (an uncredited, pre-Star Trek role) and James Whitmore’s bullets failed to stem a mutant ant invasion linked to atomic tests. But James Arness (of later Gunsmoke fame) finally routed the giant mutant ants colonizing downtown Los Angeles with an orgy of messy napalm-like flame throwers. Poison baits minimizing environmental contamination and brain-eating flies providing biological ant control look elegant in comparison. Indeed, pest control has come a long way in the half century since Rachel Carson railed against pesticides.

In her poster display at the Entomological Society of America (ESA) annual meeting in downtown Indianapolis, Kavita Sharma provided scientific details on how the brain-eating phorid flies locate fresh worker fire ant brains and turn the ants into zombies. Pheromone-like chemicals may be involved. One of the phorid fly species introduced into the U.S. from Argentina for fire ant biocontrol is literally super-efficient and would make time management experts proud. When not in the maggot stage eating ant brains, adult flies combine mating with searching out worker fire ants with nourishing brains to attack. No doubt more to come on You Tube’s Zombie Ant Channel.

The Fly Swatter

June 30, 2009

SWATTING FLIES may be a reflexive reaction to being pestered, as when bothered cattle swish their tails. Ancient Egyptian Pharaohs are usually depicted next to a high court official carrying a fly whisk. Whether nature or nurture, it is a strange news week indeed when PBS’s McLaughlin Group airs two video clips (White House Fly Swatting & PETA Protest) and discusses FLY CONTROL.

Democrat Lawrence O’Donnell said: “I completely support the president in this particular engagement.” Conservative commentator Monica Crowley opined: “The Dalai Lama would have patiently abided the fly.” Newsweek commentator Eleanor Clift acknowledged the human swatting instinct and liked PETA’s suction FLY TRAP but said: “I do have trouble killing a fly in my house. I generally open the door, try to let him out, and others come in.” Former independent presidential candidate Patrick Buchanan had the last laugh: “When you and I were kids, our parents used to UNROLL THAT FLY PAPER and all the flies stuck to it, and then you took it out and put it in the garbage.”

Real world fly control is a numbers game.  Catch (or trap) and release works better for trout in a mountain stream than for nuisance flies. What if the Prez had captured the nuisance fly and patiently taken it to the park across the street from the White House, and released it on a fresh pat of dog doo with full Secret Service protection from the environment and natural enemies?  The famous biologist Antony van Leeuwenhoek calculated that one female fly could produce 750,000 progeny in 3 months if unchecked by the environment and natural enemies (including man).

Another entomologist calculated that one female fly could beget 250 thousand billion offspring in a year. That could promote full employment by supporting a large fulltime army armed with fly swatters or catch-and-release suction traps (take your pick). DDT and pesticides were once widely seen as the remedy, but any organism reproducing as rapidly as nuisance flies becomes rapidly resistant to pesticides. Which is why Rincon-Vitova and others in the natural fly control biz usually recommend an IPM (Integrated Pest Management) approach combining remedies like traps, sticky tape and natural enemies. Entomologists like Fred Legner of the University of California, Riverside, decades ago searched nuisance fly homelands (e.g. Africa) for natural enemies and pioneered biocontrol with Spalangia and Muscidifurax species.