Archive for the 'Hymenopterans (Bees,Wasps,Ants)' Category

Giant Japanese hornet anatomy rundown

Vespa mandarinia. Photo by netman (Flickr)

The Asian giant hornet, Vespa mandarinia, is one of the largest Hymenopterans; behind only tarantula hawks (Pepsinae) I believe. They are ravenous predators of other insects (watch a honey bee hive massacre here) and can even be extremely agressive to humans, especially if a nest is disturbed. These hornets are fairly intimidating beasties to be sure, and I wouldn’t want to handle a live one. Check out this great video where someone describes the interesting features of a dead giant hornet that he found while walking in Japan.

Yikes, that stinger looks like it can do some serious damage. I wonder if there is any truth to the claims that their venom can melt flesh and kill a non-allergenic person?

Negative feedback signal in a superorganism

It has long been understood that worker honey bees, Apis mellifera, coordinate foraging for nectar using a system for dances. The best understood of these dances is the ‘waggle dance’. The waggle dance is preformed by a worker who has recently returned to the hive from a lucrative nectar source. The bee gives off an olfactory cue that tells her hive-mates to pay attention. The worker then begins to move in a rough figure-eight, vibrating her abdomen at high frequencies between the loops. The angle and duration of the vibration convey the direction and distance to a promising nectar source.

Check out this video about the waggle dance:

Honey bees also preform a tremble dance that lets workers know that a nectar-laden forager needs to be offloaded, and another dance, originally though of as a ‘begging dance’. This dance is preformed by workers that approach waggle dancers and either butt heads or climb on top of the waggler before delivering a brief 380 Hz abdominal vibration. It was originally thought that this dance was a way of begging for nectar from a laden dancer. However, research has shown that this dance does not precipitate nectar exchange.

New research has shown that the begging dance is in reality a ‘stop dance’, that tells a waggler to stop sending others to a perilous location. The research, published in Current Biology, showed that the stop dance is caused by predator and conspecific attacks on foragers. Workers returning from this dangerous location seek out waggle dancers that are sending others into danger. The stop dance decreases waggle dancing and recruitment to that location.

This stop dance is especially interesting when considered within the superorganism concept of eusocial insects. In this view, the entire colony functions as a single organism; with different colony classes acting as different cell types, and individuals analogous to single cellular units. Previously, only positive recruitment signals had been modeled at the superorganism level. Now, the stop dance adds the first example of a negative feedback signal in a superorganism. The collective interplay of waggle and stop dancing by many members of a hive therefore results in a self-organizing labor allocation system similar to those that exist at the cellular level.

References:

    Nieh, J. (2010). A Negative Feedback Signal That Is Triggered by Peril Curbs Honey Bee Recruitment Current Biology, 20 (4), 310-315 DOI: 10.1016/j.cub.2009.12.060

Aeronautic ants

Gliding ant, Cephalotes atratus. Photo by Alex Wild of Myrmecos.

The Neotropical arboreal ant, Cephalotes atratus, is a species of gliding ant. These ants live rain forest canopies where the workers spend a lot of time on exposed branches and leaves. If one these ants accidentally falls, or intentionally leaps from a branch to avoid predation, it is able to glide adeptly back to a target tree trunk or branch. A video of this gliding behavior can be seen, here. As the ant falls, it turns itself over on its back and uses its head and appendages as rudders to steer itself backwards to a tree.

These ants possess obvious evolutionary adaptations to aid their gliding behavior. Namely, the top of their head is flattened in order to generate lift as they fall upside down. In addition, the terminal segment of their hind legs is elongated and flattened (see photo below). In order to determine the importance of these specialized leg structures in generating lift and steering during descent, researchers preformed a series of experiments on the ants. They excised various body parts and then dropped the ants from the forest canopy, recording their success in gliding back to a tree.

Left: Tarsal segment of C. atratus leg viewed from the top and the side showing flattened surface. Right: Percent success of gliding back to a tree from dropped ants with various excised body parts. Adapted from Yanoviak et al., 2010.

The first thing you should note from this experiment is how damn good these ants are at gliding back to a tree when they are dropped. The unmolested control ants on the right make it to a tree over 90% of the time. However, the researchers found that if the hind legs are removed, gliding success drops to 40%, making the hind legs the most crucial appendages for steering while gliding. Also, despite the removal of a single hind leg, the other legs, or the gaster, the ants still did a pretty decent job of getting back to a tree. This success in the face of adversity suggests that steering control is highly flexible and adaptable in these worker ants. Therefore, even if a limb is lost to a predator, they are still able to glide to safety.

This research sheds light onto the complex bio-mechanics of gliding ants. They are required to preform a tightly controlled set of maneuvers as they fall in order to generate directional gliding forces. This research has shown that several structural adaptations cooperatively assist in these maneuvers.

In addition, the study of arboreal ant gliding behavior may provide clued about the origins of insect flight. Though ants are highly derived, previous fossil evidence has shown that early hexapods may have glided before developing wings. Similar gliding phases are also hypothesized in the evolutionary history of winged vertebrates. Therefore, continued research into the aerodynamic forces at work in gliding ants may suggest clues regarding the necessary stepping stones in gradual evolution of animal flight.

More on gliding ants:

References:

  • Yanoviak SP, Munk Y, Kaspari M, & Dudley R (2010). Aerial manoeuvrability in wingless gliding ants (Cephalotes atratus). Proceedings. Biological sciences / The Royal Society PMID: 20236974

Arthropod on arthropod violence

How does a swarm of army ants take down a heavily armored fresh water crab? Let’s find out…


That’s gotta be a pretty terrible way to go.

Red in mandible and pincer…

Best entomology paper concept ever?

Barron, A., Maleszka, R., Helliwell, P., & Robinson, G. (2008). Effects of cocaine on honey bee dance behaviour Journal of Experimental Biology, 212 (2), 163-168

Yes, I know those aren't honeybees. Beewolf Alexander Fleming needs to kick back too. Photo: Alvesgaspar

Via Wired

Beewolf wasps culture their own antibiotics

Beewolf Alexander Fleming discovering antibiotics, squiggly lines. Photo: Alvesgaspar

Humans have been aware of the antibiotic properties of some molds and plants for thousands of years. In classical times, fungal molds were used to treat infections. However, the true antibiotic renaissance began in 1928, when Alexander Fleming first isolated penicillin from the fungus, Penicillium notatum. Since then, penicillin and other powerful antibiotics have saved countless lives and greatly assuaged human suffering.

Antibiotics are biologically-produced chemicals that destroy or inhibit crucial components of microbial pathogens, including bacteria, fungi, and protozoans. Penicillin, for instance, works by inactivating the transpeptidase enzyme in Gram positive bacteria, preventing cell wall synthesis, and eventually killing the bacteria. Another antibiotic, Streptomycin, targets the ribosomes of all bacteria, blocking the binding of initiation factors, and preventing protein synthesis. Each class of antibiotic has a fairly unique mode of action and specific target microbes, allowing their use to be tailored on a cases by case basis.

Considering the benefits of antibiotics, it is unsurprising to learn that other organisms have evolved the means of culturing and applying these potent biochemicals. The classic examples are fungus-growing ants (article). These ants, represented by 200 species within the Attini tribe, grow subterranean fungus gardens which they cultivate for nourishment. In addition, they also culture a third symbiote, a filamentous Streptomyces bacterium that produces antibiotics to protect their fungal gardens from parasitic microbes. The ants grow these microbes on their carapaces and pass them on to their offspring.

Now, research published this week in Nature Chemical Biology, has elucidated a new case of antibiotic micro-culture in Beewolves (Philanthus sp.).

Beewolves are digger-wasps that consume nectar collected from flowers or from honeybees (Apis mellifera); which they squeeze the nectar out of after paralyzing. Female beewolves dig burrows in the ground and lay their eggs on paralyzed honeybees. When they larvae hatch they consume the bee before climbing to the ceiling of the brood chamber and forming a cocoon.

During the several-month gestation in their cocoons, the beewolf larvae are quite vulnerable to infection by microbes. In order to protect her young, the female beewolf cultures a strain of antibiotic-producing Streptomyces philanthi bacteria within specialized glands on her antenna. Prior to her larvae spinning their cocoons, she secretes her Streptomyces cultures onto the ceiling of the burrow. The bacteria are incorporated into the cocoons as the larvae spin them around themselves. The Streptomyces bacteria then excrete antibiotics into the cocoons, protecting the beewolf larvae from harmful microbes.

Left: Female beewolf excreting white Streptomyces bacteria from antennal glands. Right: magnified Streptomyces bacteria from antennal secretions, labeled with a fluorescent probe. Kroiss et al.,2010

Though it was previously shown that beewolves culture Streptomyces to protect their larvae, the nature of the antibiotic protection, provided by the symbiotic bacteria, was unknown. To that end, the current researchers used electrospray ionisation-mass spectrometry and nuclear magnetic resonance spectrometry to identify antibiotics from the beewolf cocoons. Through these ridiculously complicated spectroscopic detection techniques (they may as well be magic as far as I understand them) the researchers identified nine different antibiotic compounds in the cocoons; streptochlorin and eight piericidin derivatives. The researchers demonstrated that these antibiotics where each useful in inhibiting the growth of ten potentially harmful bacteria and fungi microbes. However, the antibiotics were found to be the most efficacious when combined into a complimentary cocktail; as they are found in situ.

The researchers then used imaging mass spectrometry (IMS) to localize the spatial distribution of the three most prevalent antibiotics on the cocoons. IMS works by scanning the surface of an object with an ion beam. This ionizes the chemicals on the object, allowing them to be detected, quantified, and localized with a mass spectrometer. The researchers found that the cocoons had even distributions of the antibiotics over their surface. In addition, they found that the majority of the antibiotics were localized on the outer layer of the cocoon. This led the researchers to hypothesize that the larvae incorporate most of the Streptomyces bacteria early in the spinning process; leaving little left over for the final, internal layers of the cocoon. This has the benefit of keeping the antibiotics on the outside of the cocoon to protect against harmful microbes, while not interfering with the growth of the larvae within.

Beewolves offer a unique case of animals culturing antibiotics for the health of developing individuals. Their antibiotic cocktail approach to microbial control is strongly akin to the synergistic ‘combination therapies’ that are increasingly popular for the treatment of human infections. These techniques have two main advantages: For one, they broaden the effectiveness of the antibiotics to include a wide variety of pathogens. In beewolves, this is advantageous because the developing larvae are threatened by diverse, opportunistic soil and entomological microbes. In addition, antibiotic cocktails are less likely to induce pathogen antibiotic resistance. Against a cocktail, a pathogen would require several simultaneous mutations in order to gain resistance.

The future of human antibiotic treatments are faced with many of the same challenges that the beewolf has risen to meet. In order to solve these problems it is crucial that we also look to nature, as Alexander Flemming did in 1928. Through the trial and error of evolution, beewolves and other organisms have been waging their own antibiotic wars against pathogens for hundreds of millions of years. We would be foolish to ignore their clever solutions to the challenges of surviving on Earth.

This post was chosen as an Editor's Selection for ResearchBlogging.orgReferences:

  • Kroiss, J., Kaltenpoth, M., Schneider, B., Schwinger, M., Hertweck, C., Maddula, R., Strohm, E., & Svatoš, A. (2010). Symbiotic streptomycetes provide antibiotic combination prophylaxis for wasp offspring Nature Chemical Biology DOI: 10.1038/nchembio.331

Weaver ants get a grip

Photo by Thomas Endlein

Thomas Endlein, a zoologist at Cambridge University, recently won the Biotechnology and Biological Sciences Research Council photography prize with this picture (left). It depicts an Asian weaver ant, Oecophylla smaragdina (Hymenoptera), hefting a 500 mg weight, equaling to about 100 times the weight of the ant. It comes as no surprise that ants are capable of great feats of strength; we often hear about ants lifting “X-hundred” times their body weight. What is astonishing about this photo, however, is that the ant is able to lift 100 times its weight whilst suspending itself upside down on a smooth, glass-like surface. How is it holding on?

Most insects are capable of adhesion to smooth surfaces like glass. On the tips of their legs ants and other insects have a specialized appendage called a tarsus. The tarsus includes claws for locomotion on rough terrain, as well as a flexible pad, called an arolium, for adhesion to smooth surfaces. The surface of the arloium varies within the insects: In flies and beetles it is covered with fine hairs, while on ants, bees, roaches, and grasshoppers it is a flat flexible cuticle. The arolium is coated with viscous secreted fluids allowing it to work like a wet suction cup.

Scanning electron micrograph of a cockroach tarsus, showing hooks and the arolium. Adapted from Clemente & Federle, 2008.

As the ant plants its foot and applies an inward-dragging force on its tarsus, the arolium passively expands, increasing suction contact with the surface (see below). It is by this mechanism that ants generate the suction-adhesion forces required to carry heavy loads over smooth surfaces. This passive expansion is especially advantageous since it automatically prevents detachment in case of sudden jostling. In addition, if the ant only applies a little pressure on the arolium it does not expand as significantly, allowing the ant to move at a brisker pace when not carrying a heavy load.

Light micrographs of a weaver ant tarsus planting on a smooth surface. The arolium pad automatically expands as the appendage is dragged on the surface. Adapted from Federle, 2002

Weaver ants, like the one in the photo at top, create elaborate woven hives out of plant leaves. Their gathering routs bring them over soil, up bark, and frequently across the undersides of smooth leaves. Therefore they have evolved a tarsus the can grip with both claws and suction in order to carry their heavy payloads home.

References:

  • Endlein, T., & Federle, W. (2007). Walking on smooth or rough ground: passive control of pretarsal attachment in ants Journal of Comparative Physiology A, 194 (1), 49-60 DOI: 10.1007/s00359-007-0287-x
  • Clemente, C., & Federle, W. (2008). Pushing versus pulling: division of labour between tarsal attachment pads in cockroaches Proceedings of the Royal Society B: Biological Sciences, 275 (1640), 1329-1336 DOI: 10.1098/rspb.2007.1660
  • Federle, W. (2002). An Integrative Study of Insect Adhesion: Mechanics and Wet Adhesion of Pretarsal Pads in Ants. Integrative and Comparative Biology, 42 (6), 1100-1106 DOI: 10.1093/icb/42.6.1100


I have moved.
Arthropoda can now be found here.

Michael Bok is a graduate student studying the visual system of mantis shrimp.

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