Wino wasp killers

Drosophila melanogaster. Photo credit: Wikipedia.

We have all heard about the possible health benefits of consuming red wine in moderation. An Emory University research team recently discovered that alcohol consumption also imparts benefits for another group of animals...fruit flies! In many households these little insects are viewed as a pesky nuisance, yet even fruit flies have their own pests: parasitoid wasps.

Parasitoid wasps don't just annoy their fly hosts, they kill them. The wasps are attracted to the smell of fermented products such as rotting fruit, where fruit flies reside. Once the female wasp finds a host she will deposit her larvae into a fruit fly maggot. The wasp larvae will develop inside of the fly, feeding on its tissues. After the wasps have matured into adults they will burst out of the dying fly's body.

The parasitoid wasp Leptopilinia boulardi. Photo credit: www.scitechdaily.com

What is a fruit fly to do? There are no urgent care clinics, but they do have a sort of "fly pharmacy" on hand. Fruit flies frequently dine on bacteria and yeast found in rotting fruit, and this meal is often accompanied by booze, ethanol to be exact. While the ethanol is a waste product of sugar-consuming yeasts, Dr. Todd Schlenke and his colleagues suspected that it could be a potent anti-parasite medication for fruit flies.

Schlenke and his team performed a series of experiments to test their hypothesis. They used Drosophila melanogaster (fruit fly host) and two different species of parasitoid wasp: Leptopilina heterotoma (generalist parasite of many Drosophila species) and Leptopilina boulardi (specialist parasite of Drosophila melanogaster).  First, the wasps were allowed to attack fly hosts from two different groups: larvae fed a non-alcoholic diet and larvae fed a six percent ethanol diet. Larvae reared on the ethanol diet harbored significantly fewer wasp eggs that did non-alcoholic larvae.

Next, the wasps were allowed to attack fly hosts from both groups to determine how host diet influenced wasp development. Wasps developing in alcohol free larvae thrived while over 60 percent of wasps in the ethanol flies died. Further, the internal organs of the less fortunate wasps had shot out of their anuses: what a way to go.

Infected fly larvae. Photo credit: www.scitechdaily.com

Schlenke and his team noticed that the timing of host alcohol consumption was key for a therapeutic effect; infected flies that subsequently drank alcohol fared well while those that switched to ethanol free diets after becoming parasitized experienced little benefit. They wondered if the flies were actively seeking alcohol to treat their infections. To test this hypothesis, the team placed parasitized and unparasitized fly larvae in bisected petri dishes that contained one side with ethanol free food and the other with ethanol rich food. First, both groups were placed on the ethanol free side. While just over 30 percent of the healthy flies migrated to the ethanol food, a whopping 80 percent of infected flies headed for the booze. They repeated the experiment, but this time they placed both fly groups on the ethanol rich side. Forty percent of the healthy flies switched to the non-alcoholic side, while some of the parasitized flies briefly left only to return to the ethanol side after 24 hours. These data suggest that the flies are deliberately seeking alcohol for therapeutic use!

Another cool aspect of their study was that the wasp species responded to the ethanol in different yet predictable ways. The generalist wasps were much harder hit by the alcohol, while the wasp specialists were more resistant. This is what we would expect given what we know about host-parasite coevolution; the generalists can go on to infect a wide range of hosts, while the specialists are much more restricted, thus there is stronger pressure on them to circumvent this anti-parasite strategy.

While we know that wild animals self-medicate when exposed to pathogens, this is the first study to demonstrate the use of alcohol as a medicine in wild animals. Since alcohol can be found in many natural habitats it is possible that other animals also use it to treat their infections. Lastly, more work is needed to determine if that glass of wine is also helping us to reduce our parasite loads!

Find out more about the flies, the wasps, and about anti-parasite behavior:

Neil F. Milan, Balint Z. Kacsoh, and Todd A. Schlenke. 2012. Alcohol consumption as self-medication against blood-borne parasites in the fruit fly. Current Biology 22: 488-493.

 http://dx.doi.org/10.1016/j.cub.2012.01.045

Brian Gray, Anne C. Jacobs, Adrienne B. Mora, and Marlene Zuk. 2012. Anti-parasite behavior. Current Biology 22: R255-R257.

http://dx.doi.org/10.1016/j.cub.2012.02.024

Parasite profile: The "brain-eating" Naegleria fowleri

Naegleria fowleri is a parasitic amoebo-flagellate that infects humans, causing severe illness and in many cases, death. This single-celled protist can be found in warm freshwater bodies, soil, and various contaminated water sources.

 Photo credit: www.soakersforum.com

Life Cycle


Naegleria fowleri can exist in three different forms during its life cycle: a cyst, a trophozoite, and a flagellate. The cyst is environmentally resistant and can protect the parasite during periods of poor environmental conditions. Once favorable conditions return, the parasite excysts as a trophozoite where it feeds and reproduces via binary fission. The trophozoite can then go on to the encysted or free-swimming flagellated form.

Life cycle stages for  N. fowleri from left to right: Cyst, trophozoite, flagellate. Photo credit: Wikipedia

How do people become infected?

Humans can become infected with N. fowleri when swimming in lakes, ponds, or untreated swimming pools, playing water sports, or even when irrigating sinuses with contaminated water. In addition, it is purported that inhaling viable cysts in dust can also lead to infection. Once the parasite contacts the nasal epithelium, it travels up the nasal mucosa and to the brain through the olfactory nerves.

Photo credit: Centers for Disease Control and Prevention

Symptoms, diagnostics, and treatment

    

Once the parasite enters the brain, it causes primary amebic meningoencephalitis (PAM), which is fatal in almost all cases. 

The onset of PAM is characterized by the following symptoms:

-fever

-headache

-changes in sense of smell or taste (due to destruction of the olfactory bulbs)

-stiff neck

-sensitivity to light

-changes in mental status

-seizures

-coma

-death  

Cerebrospinal fluid or tissue samples may be collected and analyzed for the presence of trophozoites. Treatment usually consists of administering high doses of amphotericin B and miconazole, although it is suggested that the rapid progression of infection makes successful treatment very difficult. As such, patients exhibit a high mortality rate.

Find out more about Naegleria fowleri:

Centers for Disease Control:
http://www.cdc.gov/parasites/naegleria/

National Society for Biotechnology Information:
http://www.ncbi.nlm.nih.gov/books/NBK7960/

Medscape:
http://emedicine.medscape.com/article/223910-overview

Zombifying flies and their honeybee hosts

Honey bees around the world have been dying at alarming rates, creating widespread concern and bafflement among both public and scientific communities. In the United States, symptoms of these impending declines are collectively referred to as Colony Collapse Disorder, or "CCD". CCD is primarily characterized by hive abandonment, where no or few honeybees are present in a hive even though a live queen remains.  While many factors contribute to bee declines such as mites, viruses, bacteria, fungi, and pesticides, Dr. John Hafernik, a biology professor at San Francisco State University, discovered another contender by accident: the parasitoid fly Apocephalus borealis. With the help of colleagues and his graduate student Andrew Core (the lead author), the team worked to figure out this mysterious host-parasite relationship. Recently, their fascinating findings were published in pLoS one.


It turns out that female A. borealis flies will locate honeybee hosts and land on them, depositing their eggs or "ovipositing" them into the bee's abdomen. The fly larvae develop inside of the bee and approximately seven days later they emerge, killing the bee in the process. This is very reminiscent of the movie "Aliens" isn't it?

The parasitoid fly and it's honeybee host. A) An adult female Apocephalus borealis fly. B) A female A. borealis fly deposits eggs into the abdomen of a honeybee (note how small the fly is). C) Two A. borealis fly larvae exiting the host. Photo credit: Core et al. 2012.

The even more curious thing is that the parasitized bees exhibit very unusual behavior before fully succumbing to the parasites. They abandon their hives at night; healthy bees usually leave their hives during the day to forage. They wander about aimlessly in circles, appearing disoriented and unable to properly balance. Moreover, the bees become attracted to light at nighttime. Core and colleagues suggest that the parasites may manipulate the light sensitivity or circadian rhythm of their hosts in some way, but more work is needed to fully investigate these possibilities.


The troubling realization from all of this is that honeybees usually occur in high densities, and colonies are often found in close proximity to each other. These conditions could make it very easy for fly populations to boom and further decimate honeybee populations that are already in decline. Honeybees are crucial for the pollination of many plants and agriculturally important crops, and for the production of their highly prized honey.  Research conducted by groups such as Core and colleagues is vital to the preservation of these important insects.

Find out more about colony collapse disorder:

USDA Agricultural Research Service

http://www.ars.usda.gov/News/docs.htm?docid=15572

Environmental Protection Agency:
http://www.epa.gov/pesticides/about/intheworks/honeybee.htm


Bromenshank et al. 2010:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013181

A deadly case of beer goggles

Photo credit: Darryl Gwynne/earthtimes.org

Male jewel beetles are literally dying to mate with brown beer bottles in Australia. The orange-brown coloration and manner of light reflection from dimples in the bottles resemble female jewel beetle wing covers, or "elytra". 

University of Toronto professor Darryl Gwynne and colleague David Rentz  observed this behavior while conducting field work alongside a road littered with the bottles. The bottles may act as "supernormal releasers", or exaggerated stimuli that evoke an instinctive behavioral response. In this case, the males may view the bottles as "super females" and will mate with them at all costs. These relentless mating attempts often result in death by overheating in the sun or through predation by ants. This week Gwynne and Rentz were awarded an Ig Nobel prize at Harvard University for their discovery, which was originally documented in 1983. 

Besides the mild humor involved, the discovery highlights one of the many ways that littering can adversely affect wild populations, such as the mating system of a beetle species.

Learn more about Dr. Darryl Gwynne's research:

http://labs.eeb.utoronto.ca/gwynne/

Killer Beetle Babies

Watch out, because what you eat can kill you! At least this is what Gil Wizen and Dr. Avital Gasith (Tel-Aviv University, Israel) discovered when observing interactions between amphibians and ground beetle larvae (Genus Epomis).  In an extraordinary case of predator-prey role reversal, some Epomis species have evolved anti-predator behaviors that enable them to deceive and devour their much larger would be predators. These beetle babies subsist solely on amphibians, such as frogs and salamanders, and exploit their predatory instincts by moving their antennae and mandibles, presenting themselves as tasty treats. As the unsuspecting victim is lured in, the larva heightens the excitement by flailing it's appendages more vigorously until the amphibian goes in for the kill.

Epomis larva luring a prey item through movement of antennae and mandibles. Video credit: Gil Wizen.

The tables are soon turned, however, as the larva stealthily avoids the frog's protracting tongue and harpoons the animal with hooked jaws, latching on tightly. The predator will then "suck the life" out of it's prey, ingesting bodily fluids followed by the tissues. In many instances, only bones are left behind. Those able to escape the clutches of the larvae are literally scarred, bearing the marks of being "hooked".

 Amphibian metamorph attempting to ingest an Epomis larva. Photo credit: Gil Wizen.

Leftovers. Photo credit: Gil Wizen.

Wizen and Gasith performed 382 trials where Epomis larvae and various amphibians "faced off" in test arenas. In 100% of the interactions, the beetle larvae were successful in subduing their prey, even if they were initially ingested by the amphibian! These findings have been featured in a great article published in PLoS ONE.

Predator-prey role reversal in action. Video credit: Gil Wizen.

Once the beetles have matured, they exhibit a more varied diet, however, amphibians are still not safe. Adult Epomis beetles are known to immobilize their amphibian prey with a paralyzing bite before ingesting them alive.

Mind control and body snatching, or why I chose a career in academia

When I was an undergraduate at UC Santa Barbara I had the fortunate opportunity to take a parasitology course with Dr. Armand Kuris. During this intensive course we learned that parasites face unique challenges in life, and that our typical day is drastically different from that of a parasite. For example, we may wake up everyday and go to work or school, and come home for a nice dinner before going to sleep. For most of us, these activities are not exceptionally hostile experiences.

Consider the life of a parasite. A parasite must first encounter a host, which can be quite challenging if hosts are scarce or patchy, or not around at opportune times.  Some infective stages only have a few hours to find a host before they perish in the environment. Next, the parasite must be compatible with it’s new host. Just because a parasite may find a potential home doesn't mean it will be able to live there. For example, have you ever been the unfortunate recipient of "swimmer's itch"? Perhaps you went for a dip in a lake or pond, only to be covered with small, intensely itchy bumps later on? That uncomfortable rash was caused by parasitic worms called trematodes (see below) that burrowed into your skin and tried to take up residence in your body. However, you were not a compatible host (these trematodes often use birds as their final hosts), and your immune system was able to quickly destroy the little invaders.

Another thing to keep in mind is that once a parasite successfully locates and enters an appropriate host, their new residence will soon try to kill them. Imagine living in a house that is alive and constantly assaulting you with the sole intention of ending your life. A parasite's life can be tough, and only a fraction of them may survive to reproduce.

How is one to thrive given so many obstacles? Parasites have evolved a variety of ways to locate hosts and once inside, many can combat or even evade the host immune system. They have conquered the host-time to celebrate! Well, not really. What if the parasite needs to leave it’s cozy home it worked so hard to obtain to complete its life cycle? This is the harsh reality faced by many parasites. Some must travel to mating locales that the host does not frequent, while others require transmission to additional hosts for their survival and reproduction. Still, others must find proper accommodations for their offspring inside an unwilling provider. This is when things get bizarre and where the science fiction writers come for ideas. This is why I am in graduate school.

Parasites that encounter these challenges will often hijack their hosts, manipulating their physiology, appearance, and/or behavior in ways that benefit the parasites. This phenomenon is termed “host manipulation”, and it has been identified in a wide variety of host-parasite relationships.  Manipulations may be subtle (such as an increase in host activity levels) or spectacular (such as dramatic changes in host appearance and/or behavior). Although these manifestations are highly variable, the end result is often the same: the parasite prospers at the expense of the host. I have highlighted some cool examples below.

Zombie snails

Snails get infected with the Leucochloridium spp. parasite after inadvertently ingesting their eggs as they graze on contaminated vegetation. Once ingested, the trematode eggs release larvae called miracidia that develop into sporocysts which then form broodsacs that engorge the snail's eyestalks. These broodsacs contain hundreds of infective stages called cercariae that must get to a bird to complete the lifecycle. How will they get from a snail into a bird? The infested eyestalks begin to resemble caterpillars or grubs, and the broodsacs within pulsate when exposed to light! Birds searching for a meal may mistake these bags of worms for yummy insect larvae and go in for the kill. 

Mind control by wasps

The Jewel Wasp (Ampulex compressa) mother has her work cut out for her. She must find a suitable host and somehow lure it back to her burrow where it will be held hostage, serving as a safe haven and living meal for her future offspring. What host would agree to this? Remarkably, this is not a problem for Jewel Wasps are they are powerful manipulators of the mind! When a female is ready to lay eggs, she locates an unsuspecting host for her young, usually a cockroach. She ambushes the roach, delivering a venomous sting into a specific region of it's brain. The neurotoxic venom does not paralyze the roach, but rather it makes the host submissive and seemingly undisturbed by the turn of events. The roach does not fight back, nor does it attempt to escape. Instead, it stands still while the wasp clips its antennae, drinking hemolymph ("insect circulatory fluid") from the open ends. Like leading a dog on a leash, the wasp grasps the host's antenna and leads it into her burrow. Once inside she will lay an egg on the zombified roach and the hatched larva will burrow into it's body, feasting on the internal organs. After five days or so, the larva will pupate and later exit the hollowed out carcass as an adult wasp.

Suicidal crickets

It is thought that "horsehair worms" (Phylum Nematomorpha) got their name from an old superstition that supposed the worms arose from horse hairs that fell into watering troughs. We now know that these worms do not arise from horse hairs, but are instead free-living adults that enter pools of water in search of mates for reproduction. As juveniles, the worms are obligate parasites that require an insect or crustacean for food and development (adults do not feed). However, a challenge arises once they mature and are ready to mate because their terrestrial hosts do not frequent aquatic habitats. How does one lead a cricket to water? Research suggests the worms chemically manipulate the central nervous system of their hosts, causing them to actively seek out watery areas. When the host eventually finds water it will jump in, stimulating the worm to exit the body, often killing the host in the process. 

Additional reading sources:

1. D.G. Biron, L. Marche, F. Ponton, H.D. Loxdale, N. Galeotti, L. Renault, C.
    Joly, and F. Thomas. 2005. Behavioural manipulation of a grasshopper
    harboring a hairworm: a proteomics approach. Proc. R. Soc. B. 1577: 2117-2126.

2. C. Combes. 2001. Parasitism: the ecology and evolution of intimate interactions.
    University of Chicago Press.

3. R. Gal and F. Libersat. 2010. On predatory wasps and zombie cockroaches:
    investigations of "free will" and spontaneous behavior in insects. Commun.
    Integ. Biol. 5: 458-461.
  
4. R. Gal and F. Libersat. 2010. A wasp manipulates neuronal activity in
    sub-esophageal ganglion to decrease to decrease the drive for walking in its
    cockroach prey. PLoS ONE 5 (4): e10019.

4. K.D. Lafferty and A.K. Morris. 1996. Altered behavior of parasitized killifish
    increases susceptibility to predation by bird final hosts. Ecology 77: 1390-1397.

5. J. Moore. 2002. Parasites and the behavior of animals. Oxford University Press.

6. J.C. Shaw, W.J. Korzan, R.E. Carpenter, A.M. Kuris, K.D. Lafferty,
    C.H. Summers, and O. Overli. 2009. Parasite manipulation of brain monoamines
    in California killifish (Fundulus parvipinnis) by the trematode Euhaplorchis 
    californiensis. Proc. R. Soc. B. 276: 1137-1146.


Some people doing cool work on host manipulation:

Dr. Janice Moore and colleagues:
http://www.biology.colostate.edu/faculty/pillbug

Dr. Robert Poulin and colleagues:
http://www.otago.ac.nz/Zoology/staff/otago008915.html

Dr. David G. Biron and colleagues:
http://gemi.mpl.ird.fr/OPM/Biron/biron_A.htm

Dr. Frederic Thomas and colleagues:
http://gemi.mpl.ird.fr/OPM/Thomas/thomas_A.htm

Dr. Kevin D. Lafferty and colleagues:
http://www.lifesci.ucsb.edu/eemb/labs/kuris/

Welcome to my blog!

This idea has been on my mind for a while, and I am excited to have finally brought it to fruition. My goal with this blog is to write about exciting research and science stories that are in the news. I am writing this blog for a broad audience, so a strong background in the sciences is not required. Please feel free to comment on my posts and let me know which stories you particularly like. Also, if you come across some neat science stuff that you want to share, send it my way and I will post it! Thanks for visiting and I hope you enjoy reading and learning some new things along the way!

-Adrienne