Archive for the 'Hymenopterans (Bees,Wasps,Ants)' Category
Tags: Asian Giant Hornet, Vespa
Tags: Ant, Arboreal Ant, Biomechanics, Cephalotes, Flight, Gliding
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.
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:
- Article about this research in The Guardian, here.
- Photographing gliding ants mid fall, at Myrmecos.
- The origin of insect wings, at Catalogue of Organisms
- 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
Tags: Ant, Crab, Predation
Tags: Cocaine, Dance, Honeybee
Tags: Antibiotics, Beewolf, Larvae, Philanthus, Reproduction
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.
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.
Tags: Arolium, Locomotion, Strength, Weaver Ant
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.
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.
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.
- 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
Tags: Apis, Synthetics, Vision
New research published in the Journal of Experimental Biology sheds light onto visual stimuli processing in arthropods. Researchers (Avargues-Weber et al., 2010) have shown that honeybees, Apis mellifera, are capable of complex visual processing and learning tasks that are commonly reserved for primates. With a small fraction of mammalian neural complexity, honeybees are capable of discriminating face-like visual stimuli; both between face-like and non-face-like stimuli and between variations of face like stimuli. That is, the honeybees are capable of visually discriminating and remembering one human face from another.
Of course, there is no ecological reasoning for honeybees to discriminate human faces, but the behavior is a clue about the bee’s underlying visual processing capacities. This research tells us that honeybees are able to perceive and learn, not just the individual components of a visual stimulus, but the interrelationships between them. This is the first demonstrated instance of configural processing in an arthropod.
Members of this research team first suggested that bees were capable of discriminating human faces in 2005. However, their work was criticized because it did not control for low-level stimuli (individual cues, center of gravity, symmetry, spacial frequency, and background cues) in the faces. That is, the researchers did not clearly show that the bees were actually carrying out configural processing; perceiving the interrelationships of multiple facial components processed together.
In their new paper, the researchers preformed a variety of behavioral experiments to control for low-level visual cues. They primarily used a Y-maze chamber with a choice of two visual stimuli at the end of the two branches. The bees were trained to associate a sugar reward with one of the stimuli. Afterwords, in the absence of a reward, the researchers recorded the percentage of correct choices by the bees.
First, the researchers showed that the bees could distinguish face-like and non-face-like arrangements of dashes and dots. Furthermore, they confirmed that the bees were discriminating based on the combined relationship of the eyes, nose, and mouth components of the face-like arrangements; and not just the orientation of individual components. A series of additional controls showed that the bees were not using symmetry, center of gravity, or spatial frequency cues to distinguish the stimuli. Finally, the researchers showed that the honeybees could also distinguish photos of human faces.
Some of the choices that the honeybees were able to distinguish.
This research concludes that honeybees are capable of high-level cue integration and configural visual processing. Such a capacity in honeybees is likely used for navigation and identifying flowers. The neurobiology responsible for configural visual processing is only partially understood in humans, and completely undescribed in arthropods. By working out this processing system in comparatively simple insect brains, researchers can hope to eventually apply this finding to synthetic facial recognition systems.
- Avargues-Weber, A., Portelli, G., Benard, J., Dyer, A., & Giurfa, M. (2010). Configural processing enables discrimination and categorization of face-like stimuli in honeybees Journal of Experimental Biology, 213 (4), 593-601 DOI: 10.1242/jeb.039263
- Dyer, A.G., Neumeyer, C. & Chittka, L., 2005. Honeybee (Apis mellifera) vision can discriminate between and recognise images of human faces. J Exp Biol, 208(24), 4709-4714.
Tags: Genomics, Larvae, Nasonia, Parasite, Parasitic Wasps
Last week I talked a bit about parisitoid fly larvae. Now, the genomes have has been published for three species of parisitoid wasps in Science. These guys are every bit as brutal as the flies, and then some. They forcibly inject their eggs into their insect hosts, often caterpillars. Some species inject multiple eggs while other inject a single egg that later divides into many cloned larvae that form a colonial social hierarchy within their host. Once they mature, the larvae burst out the side of their host. However, even this insult isn’t the end of the torture for the unfortunate caterpillar. The larvae employ mind controlling chemicals to force the caterpillar to use its silk to build them a cocoon, and then watch over its pupating murderers until it keels over dead.
Parisitoid wasp larvae from National Geographic’s, “In the Womb.” Watch in high quality for maximum revulsion.
Nature, you are one psychotic bitch.
Read this review for a wider overview of parasitoid wasps and their contributions to pest control and biological sciences, including discoveries made in the recent genomics work.
One interesting point jumped out at me. The parisitoid wasps are insanely diverse, with species estimates exceeding 600,000. Entomologist Michael Strand even posits that,
There’s a really compelling argument that these parasitoid wasps may be more diverse than beetles[.] Virtually every arthropod on Earth is attacked by one or more of these parasitoid wasps.
This extreme diversity seems to be tied to rapid evolvability (a concept that I have noted before in regards to arthropods) and rigid host specificity. While some wasps are generalists, laying eggs in a variety of arthropods, the vast majority parisitize a specific host species. This specificity is the result of evolutionarily optimized venoms and mind-controlling toxins, tailor made for their host species, and leading to rapid divergence of parisitoid wasp populations as they discover new host animals. This is not unlike the algal specificity of the sea slug I discussed last week. Its biology is ideally suited for maintaining chloroplasts taken up from a single species of algae.
Researchers hope to develop parisitoid wasps as a research model and exploit their prey specificity for pest control that will benefit agriculture. With bio-engineered parisitoid wasp terminators coming soon to a pasture near you, aphids and caterpillars should just cut their losses and run for their lives.