The collapse of an invader

19 January 2012 by Richard

Linepithema humile (The Argentine ant) -one of the world's most invasive species- arrived in New Zealand in 1990 and was shortly thereafter found to be present across the nation's two main islands. It immediately threatened the integrity of the natural ecosystem, displacing native species.

Scientists at the Victoria University of Wellington say that L. humile colonies in 60 locations (40% of surveyed sites) are now collapsing on their own. The leading theory is that the low genetic diversity of the invasive species confers a reduced disease resistance, and this is the most likely reason for the ant's decline.

Economic and environmental costs of invasive species can be small if populations collapse on their own accord. Good news for New Zealand; intervention for the control of L. humile was forecasted at a cost of over 35 million GBP a year.

A Kaplan-Meier survival probability estimate found the time to collapse was negatively influenced by mean maximum daily temperature and positively influenced by total annual rainfall. Mean time to population collapse ranged from 10.48 years in conditions of low rainfall and low temperature, to 17.80 years under conditions of low rainfall and high temperature. Climate change is predicted to increase the probability of Argentine ant survival.

_{Image Copyright© Royal Society Publishing.}

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Tags: Linepithema | humile | Behaviour | Ants & Humans

Ehab Abouheif on the research into supersoldier ants of the Pheidole genus

17 January 2012 by Richard

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Tags: Pheidole | Video | Supersoldier | Ehab Abouheif

Scientists create 'supersoldiers'

12 January 2012 by Richard

Pheidole are a genus of common ants comprised of over 1,000 related species. In most species of Pheidole, a developed colony has two distinct worker castes: small workers and large soldiers (or small minors and big majors). However, eight of the described species also have a novel 'supersoldier' (supermajor, if you prefer) caste in addition to the small worker and large soldier.

In these eight species, the supersoliders dwarf the large soldiers to a similar extent that the large soldiers dwarf the small workers; they're massive. They use their bulky heads to block the nest entrance from would-be invaders. It's easy to imagine how the presence of soldiers and supersoldiers might have contributed to the evolutionary success of Pheidole, the most hyperdiverse ant genus, but little is known about the underlying origins and developmental processes.

A team led by Dr Ehab Abouheif of McGill University, has recently published the results of a study where they they've attempted to understand how novel worker subcastes evolve.

They have discovered that they can "trick" (with hormonal manipulation) developing larvae of Pheidole species that normally lack the supersoldier worker caste (Pheidole morrisi in the initial experiment) to emerge as an adult ant that closely resembles the supersoldiers in the eight species that feature it.

The reason why these findings are so exciting is that it seems to indicate that deeply buried ancestral potential can be unlocked artificially. The supersoldiers emerged independently in the course of evolution for the species that have them, but this study suggests they make use of the same underlying hormonal process.

Dr Abouheif and colleagues have high hopes for the light that this may shine on the mechanism of evolution - unlocking desirable ancestral features could be key in breeding crop plants with higher nutritional value or even tackling the mechanisms that cause cancer, for example.

_{Image Copyright© Alex Wild}

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Tags: Pheidole | Evolution | Ants & Humans | Trimorphism | Supersoldier

Media lose head over parasitic fly

10 January 2012 by Richard

Last week there was something of a media foray over a fly. The fly in question, Apocephalus borealis, made the papers because it has been discovered to be parasitising honey bees - an agriculturally important and much loved insect.

The Daily Mail lead with the headline "Fly that turns bees into zombies could be the reason hives are dying, say scientists". The Mirror and Express carried similar headlines. Hundreds of outlets reported the story and scientific accuracy was a mixed bag.

Are these reactions proportionate? Entomologist Morgan Jackson had this to say on the subsequent reporting of the study "Things attacking honey bees isn't in itself news, the real news here is that the scuttle fly, A. borealis, has seemingly switched hosts, previously known to be parasitic in bumble bees, paper wasps, and even black widow spiders."

He continued "You can see why the media has fallen in love with this paper; it includes flies (which no one likes on principle), honey bees (which everyone likes on principle), CCD (which scares the daylights out of everyone) and zombies (which also scare the daylights out of everyone)."

Jackson summarises some the good, the bad and the ugly reporting over at his blog Bio in Focus and helpfully, Brian Brown, co-author of the original study and leading expert on the flies, has expanded on the research on his own blog FlyObsession in response to the media reaction and Morgan's insight. Here are some highlights:

"Unfortunately, some of the press coverage this publication is garnering is incorrect. What I'd like to concentrate on is the phoridological context of this story, particularly on the genus Apocephalus.

It seems as though Apocephalus borealis has an extremely wide range of host acceptability. Perhaps this is what allows it to switch into new hosts, such as honey bees. We know that honey bees were not the original hosts, because they are an introduced species in North America. Probably bumble bees are their main hosts, but who knows? This species is only recorded from North America.

We are currently studying the relationships among species of Apocephalus using molecular characters (DNA sequences), as well as morphology (body structure). Once we have a good phylogeny, we should know more about how the flies have shifted hosts through the group.

A. borealis is far from the only phorid that parasitizes honeybees. In South and Central America, many species of Melaloncha bee killing flies will attack honeybees.

It's great that some phorids are getting press, and I'm sure we are going to learn a lot about this species. Kudos to the other authors for their fascinating work. Don't forget, however, that Apocephalus borealis is only one of about 4000 described species, and many more have amazing life histories still to be discovered."

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Tags: Morphology & Physiology | Apocephalus | borealis

Ants are super organisms!

28 December 2011 by Richard

Colorado born Mark Moffett holds a Harvard Ph.D. in entomology having studied under the world's most respected ecologist, E.O. Wilson (being Wilson's only graduate student for the seven straight years in which he studied). Moffett is an award-winning author and one of the greatest nature photographers of his generation; he has been shooting for National Geographic for 25 years. Known to many as "Dr. Bugs" he has spent his career enthusing about ants, leading Wilson himself to conclude "I'm especially proud of Mark. He's a real naturalist, more than I."

Moffett has devoted his career to studying and talking about ants "Ants are melodrama. They forage and fight, build and destroy. You can take a box of dirt with a colony in it, stare at it for two weeks, and know the ins and outs of their society".

Wilson courted controversy back in the 70's with his book on Sociobiology (the assumption that social behaviour has resulted from evolution and can be explained as such) and thirty years later Moffett is attempting to explain the design of our urbanised world, terrorism, market economics and even our inclination toward teamwork in similar reverse anthropomorphistic thinking. He argues that these constructs come about because, like with ants, human societies of scale require them.

Moffett is developing upon the idea of William Morton Wheeler, famed Harvard Scientist of a hundred years earlier - the idea that an ant colony is a superorganism, many organisms acting together and so can be considered a single unit.

His latest book "Adventures Among Ants" (University of California Press) is out now and "Before the Swarm" is a short biographical released as a Kindle 'Single' Edition is available via Amazon.

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Tags: Mark Moffett | Behaviour | Ants & Humans | E.O. Wilson

Are Ants Conscious? (Part 2)

22 December 2011 by Richard

I acknowledged in my last post that we are not in a position to assert social insects have a consciousness, but I also alluded to the notion that it would be hasty to dismiss the possibility that they do.

The Honey Bee has a brain one cubic millimetre in size, but in this space it crams just shy of a million neurons, giving it almost 10 times the density of its mammalian counterparts. Ants have fewer neurons, with (still impressive, given their size) 250,000; two and a half times as many as a lobster. Contrast this with a human's one billion neurons, and we see that the ant and the bee are some way off in the synapse stakes. That said, it pays to remember that an Elephant has twice as many neurons as a human.

The neurons in a bees brain, as with other species, are interconnected in ways that we are yet to fully understand. Neuroscientist Christof Koch works on the neural basis of consciousness and has this to say on the subject of Bee intelligence; "Bees live in highly stratified yet flexible social organisations with group decision-making skills that rival academic, corporate or government committees in efficiency. They communicate information about the location and quality of food sources and can fly several kilometres and return to their hive. A remarkable navigational performance. Their brains seem to have incorporated a map of their environment". He goes on to comment about the possibility of bee consciousness "Given all of this ability, why does almost everybody instinctively reject the idea that bees or other insects might be conscious?"

Koch and others believe the problem stems from our inability to project onto animal species that are so different from ourselves. Being small does not mean bees cannot have subjective states or maybe even have a primitive sense of self in its own right.

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Tags: Morphology & Physiology | Behaviour

Are Ants Conscious? (Part 1)

21 December 2011 by Richard

First we must ask, what is consciousness? Consciousness is a phenomenon often described as self-awareness or wakefulness. It is the ability to experience, to feel or to have a concept of self. The mind is not directly observable; consciousness is a first-person experience. So, how do we know others have it? Other humans share an anatomy and behave in the same way as ourselves. Because of this, it is reasonable to assume other humans are also conscious. We use what scientists describe as a theory of mind to attribute mental states to others; in essence, we think, that they think, like we think - we project our experience of being conscious onto others.

For these reasons, scientific discourse is relegated to comparing reports from others with our own experience of what it is like to be conscious. This becomes somewhat more problematic when we approach the topic of non-human animals, animals who cannot tell us about their experiences. We cannot put ourselves into the mind an ant, but the question remains - is it like something to be an ant? We can only consider an ant conscious if this is so.

In 1970 Psychologist Gordon Gallup developed a test to expand upon observations made by Charles Darwin in the 19th century. The mirror test is a measure of self-awareness - animals are said to either possess or lack the ability to recognise themselves in a mirror. Whilst subject to criticism, the results of the mirror test do seem to correlate with previously held assumptions based on a scale of organism complexity and number of brain neurons (Great Apes, Rhesus Macaques, Bottlenose Dolphins, Orcas, Elephants, Barn Owls and European Magpies have been shown to pass the test). Tricky to get an ant to take a mirror test, though. Furthermore we consider social insects to have a collective or distributed intelligence which may make them a special case.

New research finding that Bees can do complex maths and recognise human faces may not tell us if bees are aware that they are aware, but may at least suggest there are many pieces of the jigsaw missing when it comes to the minds of Hymenoptera.

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Tags: Morphology & Physiology | Behaviour

Bearded Dragon catches virtual ants

18 December 2011 by Richard

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Tags: Video

Ranged warfare preferred by Cameroonian Ant

15 December 2011 by Richard

Scientists have recently discovered that a common species of Cameroonian ant prefers to fight at range when it comes to warfare with termites.

Crematogaster striatula workers hunt in packs and researchers observed groups of up to 15 ants using their built-in "gas gun" to fire venomous vapour from a safe distance at much larger opponents. The termites become paralysed or die and the ants then drag them back to the nest to be consumed.

The paralysing molecule is yet to be identified, but forms a concluding element of the research and could lead to practical applications in the next generation of insecticides.

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Tags: Crematogaster | Morphology & Physiology | Behaviour | Cameroon | striatula

The Lancet Liver Fluke and mind control

05 August 2011 by Richard

The Lancet Liver Fluke, Dicrocoelium dendriticum, is a charming animal, I'm sure you'll agree. The LLF is a parasite that spends its adult life inside the liver of cattle. Here it mates and its eggs are excreted in the host animals faeces.

The larval parasites hatch and are then ingested by a species of snail which eats cow faeces. The larva drills through the wall of the snail's gut, where it develops into the juvenile stage. It is then excreted by the snail, left behind in the slime.

The slime is a source of moisture for the common black ant of Europe, Formica fusca. Once eaten by the ant, the Fluke makes its way to the ants sub-esophageal ganglion (a cluster of nerves underneath the esophagus). Here, the fluke waits. Waits until evening, when it takes control of the ant's motor actions and steers it atop of a blade of grass. Once here, the Zombified worker ant clamps its mandibles onto the tip of the grass blade and here it stays there until dawn. The 'objective' - if it can be called that - of the Fluke is that the fusca worker is inadvertently eaten by a cow alongside the grass so the next stage of the lifecycle (propagation) for the Fluke can begin, inside the cow.

As the heat of the midday sun draws close and no cow materialises to eat the ant, the Fluke relinquishes control and the ant goes back to its normal activity within the colony. Night after night the Fluke again takes control and repeats the process of risking the ant's life for its own gain.

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Tags: Morphology & Physiology | Evolution | Behaviour

Carl Rettenmeyer

09 April 2011 by Richard

On the second anniversary of his death, today we pay tribute the life and career of the Myrmecologist Carl Rettenmeyer, who died on the 9th April 2009.

Rettenmeyer spent five decades in the rain forests of Central and South America in pursuit of the Eciton burchellii, the New World Army Ant.

He has immeasurably broadened our minds about Army Ants. The work of Rettenmeyer and his wife brought about the revelation that more than 300 species of rain forest animal depend upon a single species of army ant for their survival- a greater number of any other known life form.

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Tags: Eciton | burchelli | Carl Rettenmeyer

Time-lapse: Ants colonise a scanner

16 March 2011 by Richard

_{Courtesy of New Scientist}

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Tags: Video