̽��ֱ�� of Cambridge - Walter Federle

Vomiting bumblebees show that sweeter is not necessarily better

jg533 — Wed, 22 Jan 2020 00:01:00 +0000

Bumblebees drink nectar from flowers, then offload it in their nest – by vomiting – for use by other bees in the colony. ̽��ֱ��sugar within nectar makes it appealing, and the more sugar within the nectar, the more energy it contains. But nectar also gets more thick and sticky as the sugar content rises, and this makes it more difficult for bees to drink and regurgitate – requiring more time and energy.

Published today in the Journal of the Royal Society Interface, the study looked at the mechanics of both nectar drinking and regurgitation in one of the most common bumblebees in the UK, Bombus terrestris. It found that the best concentration of nectar for bumblebees in terms of overall energy gain is lower than might be expected. Nectar that is low in sugar is easy for bees to drink and very easy to vomit back up. As nectar gets more sugary, it gradually takes bees longer to drink, but swiftly becomes much more difficult to vomit.

“Bumblebees must strike a balance between choosing a nectar that is energy-rich, but isn’t too time-consuming to drink and offload. Nectar sugar concentration affects the speed of the bees’ foraging trips, so it influences their foraging decisions,” said Dr Jonathan Pattrick, first author of this study, formerly a PhD student based jointly in the ̽��ֱ�� of Cambridge’s departments of Plant Sciences and Zoology and now a post-doctoral researcher in the ̽��ֱ�� of Oxford’s Department of Zoology.

While it has long been known that nectar with a higher sugar concentration takes bees longer to drink, its effect on nectar regurgitation has not previously received much attention. This new information will help scientists make better predictions about which types of nectar bumblebees and other pollinators should like best, and consequently the kinds of flowers and plants they are most likely to visit. This will inform crop breeders in producing the most appealing flowers for better crop pollination and higher yields.

To conduct the research, bees were allowed to forage on sugar solutions of three different concentrations in the Department of Plant Science’s Bee Lab. While doing this, the bees were also timed and weighed. When the bees returned to their ‘nest’, the researchers watched them through a Perspex lid, timing how long it took for the bees to vomit up the nectar they had collected.

“For low strength nectar, bees had a quick vomit that only lasted a few seconds, then were back out and foraging again,” said Pattrick, “but for really thick nectar they took ages to vomit, sometimes straining for nearly a minute.”

For any given nectar concentration, bees regurgitate the nectar quicker than they initially drink it. But as nectar sugar concentration – and therefore stickiness – goes up, the rate of regurgitation decreases faster than the rate of drinking. “It’s hard to drink a thick, sticky liquid, but imagine trying to spit it out again through a straw – that would be even harder,” said Pattrick. “At a certain sugar concentration, the energy gain versus energy loss is optimised for nectar feeders.”

̽��ֱ��perfect nectar sugar concentration for the highest energy intake depends on the species drinking it, because different species feed in different ways. Bumblebees and honeybees feed by dipping their tongue repeatedly into the nectar, but regurgitate by forcing the nectar back up through a tube – just like when humans are sick. Other species such as Orchid Bees suck nectar up instead of lapping it, so struggle even more when nectar is highly concentrated. This influences nectar preference and the plants visited by different species.

Current crop breeding is focused on enhancing traits like yield and disease resistance, rather than considering pollinator preference. ̽��ֱ��new results improve predictions of the perfect nectar concentration for making the most efficient use of pollinating bumblebees.

Nectar is produced by flowers to attract pollinators, and a source of food for many species of insect, bird and mammal. ̽��ֱ��levels of the sugars sucrose, glucose and fructose within the nectar vary depending on the plant producing it.

“Studies have shown that numbers of some pollinators are going down, but there are more and more people in the world to feed. We need to make better use of the pollinators we have,” said Professor Beverley Glover in Cambridge’s Department of Plant Sciences and Director of Cambridge ̽��ֱ�� Botanic Garden, who led the study. “This research will help us understand the types of flowers and plants the bees are most likely to visit, which will inform crop breeding to make the best use of the available pollinators.”

This research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

Reference
Pattrick, J.G. et al. ‘ ̽��ֱ��mechanics of nectar offloading in the bumblebee Bombus terrestris and implications for optimal concentrations during nectar foraging.’ Interface, Jan 2020. DOI: 10.1098/rsif.2019.0632

Animal pollinators support the production of three-quarters of the world’s food crops, and many flowers produce nectar to reward the pollinators. A new study using bumblebees has found that the sweetest nectar is not necessarily the best: too much sugar slows down the bees. ̽��ֱ��results will inform breeding efforts to make crops more attractive to pollinators, boosting yields to feed our growing global population.

With really thick nectar the bees took ages to vomit, sometimes straining for nearly a minute

Jonathan Pattrick

Yani Dubin on Flickr

Bumblebee, Bombus terrestris

Improving flowers to help feed the world

A rising world population means we’ll need more food in the coming years. But much of our food relies on insect pollination, and insects are in decline around the world. Can we make flowers better at being pollinated, to help solve this problem?

This film was funded by EIT Food, as part of the #AnnualFoodAgenda project.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Suction cups that don't fall off

jg533 — Tue, 17 Dec 2019 11:49:29 +0000

̽��ֱ��aquatic larvae of the net-winged midge have the unique ability to move around at ease on rocks in torrential rivers using super-strong suction organs. Powerful modern imaging techniques have now revealed the structure of these organs in intricate detail, providing an insight into how they work so reliably.

Why Spider-Man can’t exist: Geckos are ‘size limit’ for sticking to walls

jeh98 — Mon, 18 Jan 2016 20:05:00 +0000

A new study, published today in PNAS, shows that in climbing animals ranging in size from mites to geckos, the percentage of body surface covered by adhesive footpads increases as body size increases, setting a limit to the size of animal using this strategy because larger animals would require impossibly big feet.

Dr David Labonte and his colleagues in the ̽��ֱ�� of Cambridge’s Department of Zoology found that tiny mites use approximately 200 times less of their body surface area for adhesive pads than geckos, nature's largest adhesion-based climbers. And humans? We’d need as much as 40% of our total body surface, or roughly 80% of our front, to be covered in sticky footpads if we wanted to do a convincing Spider-Man impression.

Once an animal is so big that a substantial fraction of its body surface would need to be sticky footpads, the necessary morphological changes would make the evolution of this trait impractical, suggests Labonte.

“If a human, for example, wanted to climb up a wall the way a gecko does, we’d need impractically large sticky feet – and shoes in European size 145 or US size 114,”says Walter Federle, senior author also from Cambridge’s Department of Zoology.

“As animals increase in size, the amount of body surface area per volume decreases – an ant has a lot of surface area and very little volume, and an elephant is mostly volume with not much surface area” explains Labonte.

“This poses a problem for larger climbing animals because, when they are bigger and heavier, they need more sticking power, but they have comparatively less body surface available for sticky footpads. This implies that there is a maximum size for animals climbing with sticky footpads – and that turns out to be about the size of a gecko.”

̽��ֱ��researchers compared the weight and footpad size of 225 climbing animal species including insects, frogs, spiders, lizards and even a mammal.

“We covered a range of more than seven orders of magnitude in body weight, which is roughly the same weight difference as between a cockroach and Big Ben” says Labonte.

“Although we were looking at vastly different animals – a spider and a gecko are about as different as a human is to an ant – their sticky feet are remarkably similar,” says Labonte.

“Adhesive pads of climbing animals are a prime example of convergent evolution – where multiple species have independently, through very different evolutionary histories, arrived at the same solution to a problem. When this happens, it’s a clear sign that it must be a very good solution.”

There is one other possible solution to the problem of how to stick when you’re a large animal, and that’s to make your sticky footpads even stickier.

“We noticed that within some groups of closely related species pad size was not increasing fast enough to match body size yet these animals could still stick to walls,” says Christofer Clemente, a co-author from the ̽��ֱ�� of the Sunshine Coast.

“We found that tree frogs have switched to this second option of making pads stickier rather than bigger. It’s remarkable that we see two different evolutionary solutions to the problem of getting big and sticking to walls,” says Clemente.

“Across all species the problem is solved by evolving relatively bigger pads, but this does not seem possible within closely related species, probably since the required morphological changes would be too large. Instead within these closely related groups, the pads get stickier in larger animals, but the underlying mechanisms are still unclear. This is a great example of evolutionary constraint and innovation.”

̽��ֱ��researchers say that these insights into the size limits of sticky footpads could have profound implications for developing large-scale bio-inspired adhesives, which are currently only effective on very small areas.

“Our study emphasises the importance of scaling for animal adhesion, and scaling is also essential for improving the performance of adhesives over much larger areas. There is a lot of interesting work still to be done looking into the strategies that animals use to make their footpads stickier - these would likely have very useful applications in the development of large-scale, powerful yet controllable adhesives,” says Labonte.

This study was supported by research grants from the UK Biotechnology and Biological Sciences Research Council (BB/I008667/1), the Human Frontier Science Programme (RGP0034/2012), the Denman Baynes Senior Research Fellowship, and a Discovery Early Career Research Fellowship (DE120101503).

Reference:

Labonte, D et al "Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing." PNAS 18 January 2016. DOI: 10.1073/pnas.1519459113

Inset images: Vallgatan 21D, Gothenburg, Sweden (photo by Gudbjörn Valgeirsson, footprints added by Cedric Bousquet, ̽��ֱ�� of Cambridge); How sticky footpad area changes with size (David Labonte); Diversity of sticky footpads (David Labonte).

Latest research reveals why geckos are the largest animals able to scale smooth vertical walls – even larger climbers would require unmanageably large sticky footpads. Scientists estimate that a human would need adhesive pads covering 40% of their body surface in order to walk up a wall like Spider-Man, and believe their insights have implications for the feasibility of large-scale, gecko-like adhesives.

If a human wanted to climb up a wall the way a gecko does, we’d need impractically large sticky feet – and shoes in European size 145

Walter Federle

A Hackmann & D Labonte

Gecko and ant

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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How the stick insect sticks (and unsticks) itself

jeh98 — Wed, 07 Oct 2015 13:12:35 +0000

Geckos, tree frogs, spiders and insects all share a special skill – they can walk up vertical surfaces and even upside down using adhesive pads on their feet. But geckos have ‘dry’ feet, while insects have ‘wet’ feet.

Scientists have assumed that the two groups use different mechanisms to keep their feet firmly attached to a surface, but new research from David Labonte and Dr Walter Federle in the ̽��ֱ�� of Cambridge’s Department of Zoology provides evidence that this isn’t actually the case.

“It has generally been assumed that the fluid on their feet must be involved in helping insects like stick insects adhere to a surface by capillary and viscous forces – in the same way that a beer glass will stick to a glass table if it’s wet on the bottom,” explains Labonte, lead author of the study published in Soft Matter, “but our research shows that the fluid is likely used for something else entirely – it may even help insects unstick their feet.”

By measuring how much force was required to detach the foot of a stick insect from a glass plate at different speeds and applying the theory of fracture mechanics, Labonte and Federle found that only a ‘dry’ contact model could explain the data. They also carried out a comparison of the sticking performance of wet and dry adhesive pads, which revealed that there is a striking lack of differences between the two, contrary to previous opinion.

Insects and geckos need to walk up vertical surfaces and even upside down in order to get to the places where they feed and to escape from predators. As smooth surfaces don’t allow them to grip with their claws, they need soft adhesive pads on their feet and legs. This means they need to have excellent control over adhesion – to ensure their feet stick when they want them to, but can also unstick easily to allow them to walk around or run away from predators.

“Both wet and dry adhesive pads behave in a similar way to soft, rubbery materials in that, when they are pressed against another surface, there is a large area of contact between the two surfaces,” says Labonte. Both pad types then rely on shear forces to control their stickiness: insect and gecko feet are much stickier when they are pulled towards the body.

“ ̽��ֱ��fluid that insects have on their adhesive pads doesn’t seem to increase the pads' stickiness by means of capillary or viscous forces, and the same may hold for the fluid on the feet of spiders and tree frogs.”

So what is this fluid for?

Labonte and Federle believe it may act as a ‘release layer’ to help insects unstick their feet when they want to move. “If you think of commercial adhesives, like Scotch tape, there are often bits of tape or residue left behind when you remove it quickly. But a stick insect needs to be able to unstick its feet without expending a lot of energy or leaving bits of its foot still stuck to a leaf,” explains Federle.

“ ̽��ֱ��fluid may act as a lubricant to make detachment easier, giving insects greater control over adhesion at very short timescales.”

“When the first microscopes were invented in the 17th century, one of the first things scientists looked at was a fly’s foot. ̽��ֱ��purpose of the fluid that you find on insects’ feet has remained a fascinating question ever since,” says Labonte.

But it’s not just an age-old question that this research is helping to answer. ̽��ֱ��researchers say there may be lessons to learn for modern manmade devices.

“Understanding how insects control adhesion could have applications where adhesion is needed in a dynamic context, for instance in the production of small electronic devices, where it’s necessary to pick up and place down tiny parts with ease and accuracy,” adds Federle.

This research was enabled by funding from the Biotechnology and Biological Sciences Research Council and the Human Frontier Science Programme.

Reference:

David Labonte and Walter Federle ‘Rate-dependence of ‘wet’ biological adhesives and the function of the pad secretion in insects’ Soft Matter (2015).

Inset images: Composite figure showing the adhesive pad on the foot of a stick insect (T Endlein and David Labonte); Stick insect (T Endlein); Ant's foot showing a fluid trail (Walter Federle).

New research shows the fluid found on insects’ feet does not help them adhere to vertical and inverted surfaces, as previously thought, but may in fact help them to unstick their feet more easily to allow greater control over their sticking power.

When the first microscopes were invented in the 17th century, one of the first things scientists looked at was a fly’s foot. ̽��ֱ��purpose of the fluid that you find on insects’ feet has remained a fascinating question ever since

David Labonte

Walter Federle

Ant's foot showing a fluid trail

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Close-up film shows for the first time how ants use ‘combs’ and ‘brushes’ to keep their antennae clean

jeh98 — Mon, 27 Jul 2015 15:53:30 +0000

For an insect, grooming is a serious business. If the incredibly sensitive hairs on their antennae get too dirty, they are unable to smell food, follow pheromone trails or communicate. So insects spend a significant proportion of their time just keeping themselves clean. Until now, however, no-one has really investigated the mechanics of how they actually go about this.

In a study published in Open Science, Alexander Hackmann and colleagues from the Department of Zoology have undertaken the first biomechanical investigation of how ants use different types of hairs in their cleaning apparatus to clear away dirt from their antennae.

“Insects have developed ingenious ways of cleaning very small, sensitive structures, so finding out exactly how they work could have fascinating applications for nanotechnology – where contamination of small things, especially electronic devices, is a big problem. Different insects have all kinds of different cleaning devices, but no-one has really looked at their mechanical function in detail before,” explains Hackmann.

Camponotus rufifemur ants possess a specialised cleaning structure on their front legs that is actively used to groom their antennae. A notch and spur covered in different types of hairs form a cleaning device similar in shape to a tiny lobster claw. During a cleaning movement, the antenna is pulled through the device which clears away dirt particles using ‘bristles’, a ‘comb’ and a ‘brush’.

To investigate how the different hairs work, Hackmann painstakingly constructed an experimental mechanism to mimic the ant’s movements and pull antennae through the cleaning structure under a powerful microscope. This allowed him to film the process in extreme close up and to measure the cleaning efficiency of the hairs using fluorescent particles.

What he discovered was that the three clusters of hairs perform a different function in the cleaning process. ̽��ֱ��dirty antenna surface first comes into contact with the ‘bristles’ (shown in the image in red) which scratch away the largest particles. It is then drawn past the ‘comb’ (shown in the image in blue) which removes smaller particles that get trapped between the comb hairs. Finally, it is drawn through the ‘brush’ (shown in the image in green) which removes the smallest particles.

“While the ‘bristles’ and the ‘comb’ scrape off larger particles mechanically, the ‘brush’ seems to attract smaller dirt particles from the antenna by adhesion,” says Hackmann, who works in the laboratory of Dr Walter Federle.

Where the ‘bristles’ and ‘comb’ are rounded and fairly rigid, the ‘brush’ hairs are flat, bendy and covered in ridges – this increases the surface area for contact with the dirt particles, which stick to the hairs. Researchers do not yet know what makes the ‘brush’ hairs sticky – whether it is due to electrostatic forces, sticky secretions, or a combination of factors.

“ ̽��ֱ��arrangement of ‘bristles’, ‘combs’ and ‘brush’ lets the cleaning structure work as a particle filter that can clean different sized dirt particles with a single cleaning stroke,” says Hackmann. “Modern nanofabrication techniques face similar problems with surface contamination, and as a result the fabrication of micron-scale devices requires very expensive cleanroom technology. We hope that understanding the biological system will lead to building bioinspired devices for cleaning on micro and nano scales.”

Dr Federle’s laboratory and, in part, this project receive financial support from the Biotechnology and Biological Sciences Research Council (BBSRC).

Inset images: Scanning electron micrograph of the antenna clamped by the cleaner (Alexander Hackmann); Scanning electron micrograph of the tarsal notch (Alexander Hackmann).

Reference:

Alexander Hackmann, Henry Delacave, Adam Robinson, David Labonte, Walter Federle. Functional morphology and efficiency of the antenna cleaner in Camponotus rufifemur ants. Open Science; 22 July 2015.

Using unique mechanical experiments and close-up video, Cambridge researchers have shown how ants use microscopic ‘combs’ and ‘brushes’ to keep their antennae clean, which could have applications for developing cleaners for nanotechnology.

Insects have developed ingenious ways of cleaning very small, sensitive structures, which could have fascinating applications for nanotechnology – where contamination of small things is a big problem

Alexander Hackmann

How ants use ‘combs’ and ‘brushes’ to keep their antennae clean

Alexander Hackmann

Scanning electron micrograph of the tarsal notch

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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