Parasites
edyong | July 24, 2009In Lake Alexandrina, New Zealand, a population of snails is under threat from a parasitic flatworm, a fluke aptly known as Microphallus. The fluke chemically castrates its snail host and uses its body as a living incubator for its larvae. But the snails have a weapon against these body-snatching foes - sex.
The New Zealand mud snail Potamopyrgus antipodarum is found throughout island's freshwater habitats. They breed either sexually or asexually through cloning, and the two strategies vary in prevalence throughout the lake. In the shallower waters round its margins, sex is the name of the…
edyong | June 15, 2009
In 1979, somewhere in Dartmoor, a butterfly died. That would hardly have been an exceptional event, but this individual was a Large Blue butterfly (Maculinea arion) and it was the last of its kind in the United Kingdom. Over more than a century, the Large Blue's population had been declining and it was finally declared nationally extinct 30 years ago.
Now, it's back. A bold conservation effort managed to work out the factors behind the butterfly's decline, and resurrect this vanished species. The Large Blue's reintroduction has been one of conservation's flagship successes and it was the…
sb admin | May 4, 2009
A Crematogaster ant is held up by a kleptoparasitic Milichia patrizii ant-mugging fly.
Last July, while wandering about the coastal forests of St. Lucia in eastern South Africa, I happened across an intriguing scene half-way up a spiny Acacia trunk. Some diminutive gray flies were pestering a trail of ants as they walked along the tree.
The flies' exact activities were hard to observe with the naked eye, but it looked like nothing I'd ever seen. They seemed to be grabbing ants, pinning them to the trunk, and after a few seconds letting them go again.
The macro lens on my camera serves as…
sb admin | April 13, 2009Fire ants aren't the only formicids that have to worry about parasitoid phorid flies. Many species are hosts to this diverse fly family.
Below are a pair of photos I took recently near Jujuy, Argentina showing a trio of an unidentified Pseudacteon species hovering over an ant nest. One of the flies hit her target, inserting her ovipositor between the ant's abdominal sclerites.
I don't say this about all my images, but these shots were truly lucky. The flies are much smaller (1mm) and more erratic than the phorids I posted previously. The oviposition itself took a fraction of a second,…
sb admin | April 10, 2009In Argentina, an ant-decapitating fly (Pseudacteon sp.) attempts to separate a fire ant (Solenopsis sp.) from her nestmates:
More photos- and the story behind them- below.
An ant burdened with prey is the easiest target of all:
The ants aren't defenseless. The classic "run-and-hide" works well enough:
What's the deal with the dreaded Ant-Decapitating Flies? The University of Texas Fire Ant Project explains:
"Female phorid flies are attracted to fire ants swarming over a disturbed mound or foraging along a trail to food. They hover over ants looking for a preferred individual. (Each…
edyong | March 20, 2009There are so many fascinating stories about parasitic wasps that they have become a regular feature in this blog. Usually, their prey come off poorly in these tales, with caterpillars being reduced to little more than living, paralysed larders for macabre wasp grubs. But not always - some hosts don't take the invasion of their bodies lying down. This post is an attempt to redress the balance between parasite and host, by telling the story of the caterpillar that fights back... with medicine.
One species of tiger moth, Grammia incorrupta, has a fuzzy caterpillar called the woolly bear. Like…
edyong | February 28, 2009Conspiracy theories, TV thrillers and airport novels are full of the idea that the world is secretly run by a hidden society. We have come up with many names for this shadowy cabal of puppet-masters - the Illuminati, the Freemasons, and more. But a better name would be 'parasites'.
Every animal and plant is afflicted by parasites. The vast majority are simple, degenerate creatures, small in size and limited in intelligence. They affect our health and development, and even our behaviour and culture. And by pulling the strings of key species, parasites can change the face of entire habitats.In…
edyong | February 21, 2009
When people say that every cloud has a silver lining, they probably aren't thinking about herpes at the time. Herpes may be unpleasant, but the viruses that cause it and related diseases could have a bright side. In mice at least, they provide resistance against bacteria, including the bubonic plague.
Herpes is one of a number of itchy, blistering diseases, caused by the group of viruses aptly-named herpesviruses. Eight members infect humans and cause a range of illnesses including glandular fever, chickenpox, shingles and, of course, herpes itself.
Almost everyone gets infected by one of…
edyong | February 19, 2009It's a scene straight out of a horror film - you look around and see dead bodies everywhere. They haven't just been killed either, they've been hollowed out from the inside-out leaving behind grotesque mummified shells. What would you do if you were confronted with such a macabre scene? Flee? Well, if you were an aphid, you'd probably just feel relieved and go about your business. Aphids, it seems, find security among the corpses of their peers.
Aphids, like almost all insects, are the targets of parasitic wasps that implant eggs inside their bodies. On hatching, the wasp grubs use the aphid…
awild | February 12, 2009
Here's a sharper version:
Parasitic Cotesia wasp attacks a Manduca larva
The story itself is amazing. It's been known for some time that Ichneumonid and Braconid wasps inject circular strands of DNA- called polydnaviruses- into their host insects along with their eggs. This DNA is encoded by the wasp genome but acts like a virus in their hosts, dismantling the immune system to protect the developing wasp larvae. In a study out this week in Science, a team headed by Jean-Michel Drezen pinpointed the origin of the polydnavirus as being a type of nudivirus. It seems that some ancient…
edyong | February 12, 2009This is the seventh of eight posts on evolutionary research to celebrate Darwin's bicentennial. It combines many of my favourite topics - symbiosis, horizontal gene transfer, parasitic wasps and viruses.
Parasitic wasps make a living by snatching the bodies of other insects and using them as living incubators for their grubs. Some species target caterpillars, and subdue them with a biological weapon. They inject the victim with "virus-like particles" called polydnaviruses (PDVs), which weaken its immune system and leave the wasp grub to develop unopposed. Without the infection, the wasp egg…
edyong | February 11, 2009This is the fifth of eight posts on evolutionary research to celebrate Darwin's bicentennial.
Life can sometimes be a futile contest. Throughout the natural world, pairs of species are locked in an evolutionary arms race where both competitors must continuously evolve new adaptations just to avoid ceding ground. Any advantage is temporary as every adaptive move from a predator or parasite is quickly neutralised by a counter-move from its prey or host. Coerced onward by the indifferent force of natural selection, neither side can withdraw from the stalemate.
These patterns of evolution are…
edyong | February 9, 2009This is the second of eight posts on evolutionary research to celebrate Darwin's bicentennial.
What do you get when one species splits into separate lineages? Two species? Think bigger...
When new species arise, they can set off evolutionary chain reactions that cause even more new species to spring forth - fresh buds on the tree of life create conditions that encourage more budding on different branches.
Biologists have long suspected that these "cascades of speciation" exist but have struggled to test them. Enter Andrew Forbes from the University of Notre Dame - his team of has found a…
edyong | November 21, 2008Over the past decade, some coastal waters have started turning red with alarming frequency. The cause is not some Biblical plague, but dense concentrations of microscopic algae called dinoflagellates. Red tides can often contain more than a million of these cells in a mere millilitre of water. Many are harmless and essential parts of the ocean environment, but others produce toxins that can kill local wildlife and risk the health of humans who eat their poisoned flesh.
These "harmful algal blooms" are more common in warm waters that mix poorly and are unusually rich in nutrients. Their…
edyong | October 29, 2008Our amphibians are not doing well. Populations of frogs, toads, salamanders and newts the world over are falling dramatically. Their moist, permeable skins and their need for water to reproduce make them vulnerable to a multitude of threats including drought brought on by climate change, a deadly fungus, and other infectious diseases. Now, we can point an accusatory finger at another culprit - a chemical called atrazine that is second most commonly used pesticide in the United States, and perhaps the world.
Jason Rohr and colleagues from the University of Florida found that atrazine exposes…
edyong | October 9, 2008
Throughout the day, our skins are constantly sending out messages that we are completely oblivious to. The message is written in chemical form and it says, "Here I am. Come and get me". We neither see nor hear these signals but other creatures do, and they slither, crawl and swim our way in response.
These creatures are nematodes, a group of worms that are some of the most common animals on the planet. The vast majority of nematode species are parasites, and hundreds of species count humans among their potential hosts. In the developing countries of the tropics and sub-tropics, parasitic…
edyong | October 5, 2008
We like to think that we are masters of our own fates. The thought that others might be instead controlling our actions makes us uneasy. We rail against nanny states, we react badly to media hype and we are appalled at the idea of brainwashing. But words and images are not the only things that can affect our brains and thoughts. Other animals - parasites - can do this too. According to research by Kevin Lafferty from the University of California, Santa Barbara, a common brain parasite, Toxoplasma gondii, could be influencing human culture across the globe.
Toxoplasma gondii is a single-…
edyong | August 6, 2008Viruses may cause disease but some can fall ill themselves. For the first time, a group of scientists have discovered a virus that targets other viruses. This new virus-of-viruses was discovered by Bernard La Scola and Christelle Desnues at the University of the Mediterranean, who have playfully named it Sputnik, after the Russian for "fellow traveller". It is so unique that they have classified it in an entirely new family - the "virophages" - in honour of the similarities it shares with the bacteriophage viruses that use bacteria as hosts.
The story of Sputnik started in 1992 with some…