Q is for Queen Bumblebee
By amb206 from University of Cambridge - Department of Zoology. Published on Sep 23, 2015.
Each autumn, colonies of bumblebees die. All, that is, apart from the gravid (egg-carrying) queens who survive the winter in tiny burrows in the ground. Early in the spring, the queen emerges to start making a nest in which to lay her eggs. To do so, she needs the energy provided by nectar and pollen. If she can’t find enough flowers from which to gather these resources, she will die – and the next generation she is carrying will die too.
Bumblebees are among the UK’s estimated 1,500 species of wild pollinators and play a vital role in the environment. They transfer pollen from plant to plant – and thus ensure that plants reproduce. An estimated 75% of the crops we eat depend on pollination. Bumblebees are particularly important pollinators of beans, raspberries and tomatoes. Uniquely, they are capable of ‘buzz pollination’, producing a high-pitched buzz which releases pollen from pollen-containing tubes inside some flowers. Tomatoes are pollinated like this.
Over the past 80 years or so, there has been a dramatic decline in the distributions of some bumblebee species. Two of the 26 species of bumblebee once common in the UK are now extinct. Scientists think that the factors behind this decline are several and interconnected. Most obvious is the loss of wild flower meadows which have disappeared as farming has become more intensive and fields made larger by the removal of hedgerows. Although many British gardens burst with flowers, many of the showy favourites (such as pansies and begonias) produce little pollen or nectar.
A recent report by Dr Lynn Dicks (Department of Zoology) and staff at Natural England makes an important contribution to the development of nation-wide strategies to halt – and reverse – the loss of wild pollinators such as bumblebees. In 2013, a rare and time-limited opportunity opened up for scientists to contribute to the development of an ‘agri-environment package’ for wild pollinators as part of the new Countryside Stewardship scheme, launched earlier this year.
As an expert in the ecology of flower-visiting insects, Dicks used this ‘policy window’ to bring together a wide range of available information and ask key questions about wild pollinators and their relationship with the farmed environment. In providing tentative answers to these questions, her paper provides ballpark figures on aspects of land management that determine population levels of wild pollinators, including bumblebees, and bolsters arguments for policies that encourage farmers to sow a mix of wild flowers.
“An agri-environment package is a bundle of management options that supply sufficient resources to support a target group of species. Data from a similar package, aimed at helping farmers provide resources for species of birds known to be declining, are not yet publically available. But some of the measures in the package are known to have led to an upturn in numbers of six target species – including skylarks and yellowhammers – which is most encouraging,” says Dicks.
“We depend on pollinators for food production so it’s in our interests to halt drops in numbers. If species are declining, it’s because they lack specific resources – or because other factors are reducing their numbers faster than they can reproduce. Some risks to pollinators – notably pesticides and climate change – are difficult to quantify and politically challenging. An alternative is to focus policy on providing the resources that are lacking – such as nectar-rich flowers.”
The most critical period for bumblebee survival is March and April when the queens that have hibernated over the winter need access to enough nectar and pollen to raise their first batch of workers within an estimated 1km radius of their nests. The first batch of eggs laid by the queen become female workers whose role is to feed the new colony by visiting flowers to gather nectar. Throughout the summer the queen will produce further batches of eggs, seldom leaving the nest. She will eventually control a nest of as many as 400 individuals, including new queens. Honeybee hives, in comparison, typically contain around 50,000 bees.
Many commercial crops flower several weeks after the queen bumblebees are most in need of nectar. Oil seed rape, for example, produces its bright yellow flowers in May and June. Nectar and pollen provided by these crops are valuable to later batches of bumblebees. However, the first batch of bumblebees relies on plants that flower in early spring – including those associated with rough land (such as comfrey and white deadnettle) and hedgerow species (such as willow, hawthorn and blackthorn).
Recent research revealed that wild pollinators provide a much more important service to commercial crops than previously thought. Dicks’ report identifies opportunities for enhancing the environment for six species of wild bee including three species of bumblebee by sowing wild flowers and providing environments for nests.
She compiled and analysed data from a number of wildlife conservation and research organisations, including the Bumblebee Conservation Trust, to build an overall picture of the resources that these insects need to flourish.
By calculating the pollen demands of individual bees, and the resulting demand for flowers, Dicks has come up with some approximate figures in terms of the percentage of land and hedgerow needed to resource a healthy population of selected wild pollinators. Using a 100-hectare block of land as the basis for calculations, she estimates that the provision of a 2% flower-rich habitat and 1km flowering hedgerow will supply the six pollinator species with enough pollen to feed their larvae.
“We suggest that farmers sow headlands, field corners and other areas with mixes that will flower in the summer months, but they also need to manage hedgerows, woodland edges, margins and verges to enhance early and late flowering species and provide nesting and hibernating opportunities,” says Dicks. “It’s really important that the packages offered to farmers through the Countryside Stewardship scheme are easy to implement and well supported by financial incentives and advice. Because we are learning more all the time about the interaction between wild pollinators and the environment, schemes also need to have built-in flexibility.”
Next in the Cambridge Animal Alphabet: R is for an animal that is often found among the pages of children's literature.
Have you missed the series so far? Catch up on Medium here.
Inset images: Bombus pascuorum (Joan Chaplin); Bombus lapidarius (Tessa Bramall).
The Cambridge Animal Alphabet series celebrates Cambridge's connections with animals through literature, art, science and society. Here, Q is for Queen Bumblebee, one of the UK's 1,500 species of wild pollinators that play a vital role in the environment and food production.
Love’s Labours: study shows male lizards risk becoming lunch for a bird in order to attract a mate
By jeh98 from University of Cambridge - Department of Zoology. Published on Sep 22, 2015.
In the animal kingdom, the flashiest males often have more luck attracting a mate. But when your predators hunt by sight, this can pose an interesting problem.
Like many species, lizards use bright colours for sexual signalling to attract females and intimidate rival males. A new study published in Ecology and Evolution by Kate Marshall from the University of Cambridge’s Department of Zoology and Martin Stevens from the University of Exeter’s Centre for Ecology and Conservation has provided evidence that this signalling comes at a cost.
Using models that replicated the colouration of male and female wall lizards found on the Greek islands of Skopelos and Syros, they found that the male lizard models were less well camouflaged against their habitat and more likely to fall prey to bird attacks.
Marshall, lead author of the study, explains: “we wanted to get to the origins of colour evolution; to find out what is causing colour variation between these lizards. We wanted to know whether natural selection favours camouflage, and whether the conflicting need to have bright sexual signals might impair its effectiveness.
“It has previously been assumed that conspicuous male colours are costly to survival, but this hasn’t been tested before among these specific lizards living on different islands, and in general rarely in a way that takes into account the particular sensitivities of avian vision.”
Birds see the world differently from you or I: they are able to see ultraviolet (UV) light whereas we cannot, which means they perceive colour (and camouflage) in a very different way. To test whether the males really are more visible to feathered predators, the researchers had to develop clay models that accurately replicated the lizards’ colour to a bird’s eye.
Using visual modelling, Marshall and her colleagues painstakingly tested around 300 colour variations to find ones that matched the male and female colours in order to make the 600 clay lizards used in the study.
Marshall comments: “it was important to get a clay colour that would be indistinguishable from a real lizard to a bird’s eyes: we even tried using a paint colour chart, but they all reflected too much UV. To us the models may not look like very good likenesses, but to a bird the models should have looked the same colour as the real lizards.”
Marshall and her field assistant, Kate Philpot, placed the male and female lizard models in ten sites on each of the two islands and checked them every 24 hours over five days to see which had been attacked by birds.
“The models that had been attacked showed signs of beak marks, particularly around the head, and some had been decapitated,” explains Marshall. “We even found a few heads in different fields to the bodies.”
“The fact that the birds focused their attacks on the heads of the models also shows us that they perceived them as real lizards because that is how they would attack real prey,” she adds.
At the end of the study, the researchers found that the models with male colouration had been attacked more than the models with female colouration.
Marshall and the team also tested how conspicuous the models were against their real backgrounds using further modelling of avian vision, and found that the male models were less camouflaged than the females.
“In females, selection seems to have favoured better camouflage to avoid attack from avian predators. But in males, being bright and conspicuous also appears to be important even though this heightens the risk of being spotted by birds,” says Marshall.
However, it is not entirely a tale of woe for the male Aegean wall lizard. Despite being attacked more than the females by predatory birds, 83% of the male lizard models survived over the course of the five-day experiment. Marshall explains that this may indicate that males have colour adaptations that balance the contradictory needs to attract a mate and to avoid becoming lunch.
“In past work we’ve found these lizards have evolved bright colours on their sides, which are more visible to other lizards on the ground than to birds hunting from above,” explains Marshall. “The visual system of lizards is different again from birds, such as through increased sensitivity to UV, so the colour on their backs is more obvious to other lizards than to birds. Such selective “tuning” of colours to the eyes of different observers might provide at least some camouflage against dangerous predators that sneakily eavesdrop on the bright signals of their prey.”
“With these models we were only able to replicate the overall colour of the lizards rather than their patterns, so it would be interesting to investigate further whether these patterns affect the survival rates of lizard models,” she adds. “It would also be great to apply this type of experiment to other questions, such as how different environments affect the amount of predation that prey animals experience.”
Reference: Marshall, K et al. “Conspicuous male coloration impairs survival against avian predators in Aegean wall lizards, Podarcis erhardii” Ecology and Evolution (September 2015). DOI: http://onlinelibrary.wiley.com/doi/10.1002/ece3.1650/full
The research was enabled by funding from the Biotechnology and Biological Sciences Research Council, the British Herpetological Society, the Cambridge Philosophical Society, and Magdalene College, Cambridge.
Inset images: Tetrahedral plot of avian vision (Kate Marshall et al); Models showing signs of bird attack (Kate Marshall et al); Males, females and their corresponding models (Kate Marshall et al).
New research shows male lizards are more likely than females to be attacked by predators because the bright colours they need to attract a mate also make them more conspicuous to birds.
Burying beetles: could being a good father send you to an early grave?
By fpjl2 from University of Cambridge - Department of Zoology. Published on Sep 22, 2015.
When a good insect father pairs with a bad mother, he risks being exploited by her for childcare and could bear the ultimate cost by dying young.
A new study carried out with burying beetles also shows that bad parenting creates bad parents-to-be, while well-cared for larvae mature into high quality parents.
The research is published today in the open access journal eLife.
“Parents obviously play a huge role in determining the characteristics of their offspring,” said lead researcher Professor Rebecca Kilner from the Department of Zoology at the University of Cambridge.
“The aim of our study was to investigate non-genetic ways that parents achieve this.”
This is important because non-genetic inheritance could speed up the rate at which animal behaviour evolves and adapts in a rapidly changing world
Whether examining mothers or fathers, the research team found that individuals that received no care as larvae were less effective at raising a large brood as parents, and died younger. In contrast, high quality care not only produces a larger brood, but individual offspring with a higher mass. This is consistent with previous studies.
“We found that parental care provides a mechanism for non-genetic inheritance. Good quality parents produce offspring that become good parents themselves, while offspring that receive poor parenting then become low quality parents. Our experiments show how parental care allows offspring to inherit characteristics of their parents, but non-genetically,” Kilner said.
However, the team also found that offspring pay a cost for receiving high quality care, because it makes them vulnerable to exploitation if they pair up with a lower quality partner. This may explain why animals often choose a mate that is willing to put in a similar amount of effort as them as a parent. In this way, they are less vulnerable to exploitation.
The burying beetle, Nicrophorus vespilloides, uses the carcass of a small vertebrate such as a mouse as an edible nest for its young. As its name suggests, a breeding pair buries the carcass and preserves it with an antibacterial secretion. The mother lays eggs nearby in the soil, and the larvae crawl to the carcass when they hatch. Although the larvae can feed themselves, they also beg both parents for partly-digested food from the carcass.
In the current study, when males were paired with females that had received no post-hatching care as larvae, they had significantly shorter lives than those whose partners had received more care. The most likely explanation is that males with low quality partners put more effort into parental duties to compensate for the shortcomings of their mate, and paid the price by dying younger.
Story taken from an eLife press release.
New research shows beetles that received no care as larvae were less effective at raising a large brood as parents. Males paired with ‘low quality’ females - those that received no care as larvae - paid the price by dying younger, researchers found.
Global consortium rewrites the ‘cartography’ of dengue virus
By cjb250 from University of Cambridge - Department of Zoology. Published on Sep 17, 2015.
Dengue virus infects up to 390 million people each year. Around a quarter of these people will experience fever, headaches and joint pains, but approximately 500,000 people will experience potentially life-threatening complications, including haemorrhage and shock, where dangerously low blood pressure occurs. There are currently no vaccines against infection with dengue virus.
For decades, scientists have thought that there are four genetically-distinct types of the virus, known as serotypes, and that antigenic differences between the types play a key role in the severity of disease, its epidemiology and how the virus evolves – and hence these differences would be important in vaccine design.
When we become infected, our immune system sends out antibodies to try and identify the nature of the infection. If it is a pathogen – a virus or bacteria – that we have previously encountered, the antibodies will recognise the invader by antigens on its surface and set of a cascade of defences to prevent the infection taking hold. However, as pathogens evolve, they can change their antigens and disguise themselves against detection.
One of the unusual aspects of dengue is that in some cases when an individual becomes infected for a second time, rather than being immune to infection, the disease can be much more severe. One hypothesis to explain this is that the antibodies produced in response to infection with one strain of the virus somehow allow viruses of a different strain to enter undetected into cells, implying that antigenic differences between the serotypes are important.
Researchers from the Dengue Antigenic Cartography Consortium, writing in today’s edition of Science, analysed 47 strains of dengue virus with 148 samples taken from both humans and primates to see whether they indeed fit into four distinct types. The researchers found a significant amount of antigenic difference within each dengue serotype – in fact, the amount of difference within each serotype was of a similar order to that between the different types. This implies that an individual infected with one type may not be protected against antigenically different viruses of the same type, and that in some cases the individual may be protected against some antigenically similar strains of a different type.
Leah Katzelnick, a researcher from the Department of Zoology at the University of Cambridge, who began studying dengue after herself contracting the disease, says: “We were surprised at how much variation we saw not only between the existing four known types of dengue, but also within each type. This means that hypotheses that put antigenic differences at the centre of dengue epidemiology are now back on the table.”
Senior author Professor Derek Smith, also from the Department of Zoology at Cambridge, adds: “This discovery is in many ways similar to when researchers first began using the microscope – it will give us a new way of looking at dengue and in much closer detail than before. Now we can ask – and potentially answer – the interesting questions about how the virus evolves and, importantly, why a first dengue infection is often mild while many second infections are life-threatening.”
Characterising the global variation of dengue viruses will be important for understanding where current vaccines will be protective. In the future, it may assist us in determining which strain to include in vaccination programmes and to follow the virus as it evolves, say the researchers.
The Dengue Antigenic Cartography Consortium is an open, global collaboration of dengue researchers set up in 2011 to establish how large samples of dengue isolates relate to one another antigenically. The Consortium currently consists of epidemiologists, clinicians, geneticists, cartographers, molecular biologists, government officials, and vaccine developers, based in laboratories in Africa, the Americas, Asia, Europe, and the Pacific. As results from the project become available, they are shared with members of the Consortium.
Katzelnick, LC et al. Dengue viruses cluster antigenically but not as discrete serotypes. Science; 17 Sept 2015.
An international consortium of laboratories worldwide that are studying the differences among dengue viruses has shown that while the long-held view that there are four genetically-distinct types of the virus holds, far more important are the differences in their antigenic properties – the ‘coats’ that the viruses wear that help our immune systems identify them.
Neural circuit in the cricket brain detects the rhythm of the right mating call
By sc604 from University of Cambridge - Department of Zoology. Published on Sep 11, 2015.
Scientists have identified an ingeniously elegant brain circuit consisting of just five nerve cells that allows female crickets to automatically identify the chirps of males from the same species through the rhythmic pulses hidden within the mating call.
The circuit uses a time delay mechanism to match the gaps between pulses in a species-specific chirp – gaps of just few milliseconds. The circuit delays a pulse by the exact between-pulse gap, so that, if it coincides with the next pulse coming in, the same species signal is confirmed.
It’s one of the first times a brain circuit consisting of individual neurons that identifies an acoustic rhythm has been characterised. The results are reported today (11 September) in the journal Science Advances.
Using tiny electrodes, scientists from Cambridge University’s Department of Zoology explored the brain of female crickets for individual auditory neurons responding to digitally-manipulated cricket chirps (even a relatively simple organism such as a cricket still has a brain containing up to a million neurons).
Once located, the nerve cells were stained with fluorescent dye. By monitoring how each neuron responded to the sound pulses of the cricket chirps, scientists were able to work out the sequence the neurons fired in, enabling them to unpick the time delay logic of the circuit.
Sound processing starts in hearing organs, but the temporal, rhythmic features of sound signals – vital to all acoustic communication from birdsong to spoken language – are processed in the central auditory system of the brain.
Scientists say that the simple, time-coded neural network discovered in the brain of crickets may be an example of fundamental neural circuitry that identifies sound rhythms and patterns, and could be the basis for “complex and elaborate neuronal systems” in vertebrates.
“Compared to our complex language, crickets only have a few songs which they have to recognise and process, so, by looking at their much simpler brain, we aim to understand how neurons process sound signals,” said senior author Dr Berthold Hedwig.
Like in Morse code, contained within each cricket chirp are several pulses, interspersed by gaps of a few milliseconds. It’s the varying length of the gaps between pulses that is each species’ unique rhythm.
It is this ‘Morse code’ that gets read by the five-neuron circuit in the female brain.
Crickets’ ears are located on their front legs. On hearing a sound like a chirp, nerve cells respond and carry the information to the thoracic segment, and on to the brain.
Once there, the auditory circuit splits and sends the information into two branches:
One branch (consisting of two neurons) acts as a delay line, holding up the processing of the signal by the same amount of time as the interval between pulses – a mechanism specific to a cricket species’ chirp. The other branch sends the signal straight through to a ‘coincidence detector’ neuron.
When a second pulse comes in, it too is split, and part of the signal goes straight through to the coincidence detector. If the second pulse and the delayed signal from the first pulse ‘coincide’ within the detector neuron, then the circuit has a match for the pulse time-code within the chirp of their species, and a final output neuron fires up, when the female listens to the correct sound pattern.
“Once the circuit has a second pulse, it can define the rhythm. The first pulse is initial excitation; the second pulse is then superimposed with the delayed part of the first. The output neuron only produces a strong response if the pulses collide at the coincidence detector, meaning the timing is locked in, and the mating call is a species match,” said Hedwig.
“With hindsight, I would say it’s impossible to make the circuitry any simpler – it’s the minimum number of elements that are required to do the processing. That’s the beauty of nature, it comes up with the most simple and elegant ways of dealing with and processing information,” he said.
To find the most effective sound pattern, the scientists digitally manipulated the natural pulse patterns and played the various patterns to female crickets mounted atop a trackball inside an acoustic chamber containing precisely located speakers.
If a particular rhythm of pulses triggered the female to set off in the direction of that speaker, the trackball recorded reaction times and direction.
Once they had honed the pulse patterns, the team played them to female crickets in modified mini-chambers with opened-up heads and brains exposed for the experiments.
Microelectrodes allowed them to record the key auditory neurons (“it takes a couple of hours to find the right neuron in a cricket brain”), tag and dye them, and piece together the neural circuitry that reads rhythmic pulses occurring at intervals of few milliseconds in male cricket chirps.
Added Hedwig: “Through this series of experiments we have identified a delay mechanism within a neuronal circuit for auditory processing – something that was first hypothesised over 25 years ago. This time delay circuitry could be quite fundamental as an example for other types of neuronal processing in other, perhaps much larger, brains as well.”
The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).
Stefan Schöneich, Konstantinos Kostarakos, Berthold Hedwig. An auditory feature detection circuit for sound pattern recognition. Science Advances (2015). DOI: 10.1126/sciadv.1500325
Delay mechanism within elegant brain circuit consisting of just five neurons means female crickets can automatically detect chirps of males from same species. Scientists say this example of simple neural circuitry could be “fundamental” for other types of information processing in much larger brains.
Paying farmers to help the environment works, but ‘perverse’ subsidies must be balanced
By sc604 from University of Cambridge - Department of Zoology. Published on Sep 09, 2015.
New research suggests that offering financial incentives for farming industries to mitigate the impact agriculture has on the environment, by reducing fertiliser use and ‘sparing’ land for conservation, for example, actually has a positive effect on critical areas such as greenhouse gas reduction and increased biodiversity.
It has been a point of contention whether such ‘cash for conservation’ initiatives succeed. For the latest study, researchers aggregated investment in environmental incentives at a national level for the first time, and, by comparing them to broad trends in environmental outcomes, found that paying the agriculture industry to help the environment seems to be working.
However, the research team also mapped the proportion of global agricultural production reinvested in environmental incentives, and compared it to the proportion gifted to the industry through government subsidies. As expressed in pie charts, the results show big wedges of subsidy stacked on top of barely perceptible slivers of environmental investment.
For example, around 20% of the value of agriculture production in the EU is subsidised by the taxpayer. However, less than 1% goes towards mitigating the toll farming takes on the natural world – despite agriculture contributing more to environmental degradation than any other economic sector, say researchers.
The team describe current agriculture funding models as ‘perverse subsidies’: promoting negative actions in both the long and short term by being bad for the environment and costly to the economy.
They argue for a redressing of the massive imbalance between government money spent on farming subsidies, and that spent on lessening the damage farming does to the environment.
Consumption of environmental services, such as water (crop irrigation alone counts for 70% of the world’s freshwater withdrawals), should be taxed, say the researchers, and any subsidies should be paid on the proviso that they are as much for protecting the land as for farming it.
“Our results show that paying farmers to do things that are good for the environment actually seems to work when averaged across national scales,” said lead author Dr Andrew Tanentzap.
“In many parts of the world, governments already provide huge subsidies to the agriculture industry; if we are paying people to be farmers, part of that payment – indeed, part of the job of a farmer – needs to be protecting the countryside as well as farming it,” he said. “We need a shift in what it means to be a farmer.”
The work, conducted by researchers from Cambridge University’s departments of Plant Sciences and Zoology, is published today in the open access journal PLOS Biology.
While national data for environmental performance is limited and difficult to quantify, the research team were able to plot investment in two key agri-environment schemes, land ‘retirement’ for conservation and limiting fertiliser use, against national trends for farmland bird populations and emissions from synthetic fertiliser across landmasses including the US, Canada, Australia and Europe.
They found that, broadly speaking, higher national investment in these environmentally-friendly incentive schemes over a five-year period correlated with increased levels of bird biodiversity and lower rates of gas emissions from farming.
“There’s controversy around whether such environmental incentives actually work at a local scale. What we’ve done is average out the local effects to pull out what’s happening on a very large scale, and it looks like there are benefits to paying farmers to be kinder to the environment,” said Tanentzap.
However, Tanentzap points out that paying farmers to be more environmentally-friendly won’t solve the problem of food security, and if these schemes reduce crop yields it may result in increased production elsewhere: “displacing the impacts that we are paying some farmers to mitigate”. He says that, in the worst cases, this results in further land being sucked into the agricultural churn.
“A result of many agri-environment schemes is the spreading out – or ‘sharing’ – of land for both farming and the natural environment. A lot of research, much of it driven by conservation scientists here in Cambridge, shows that this is less effective than simply removing the land from production – ‘sparing’ it for conservation.”
“The most logical solution would be to intensify production on existing lands, trying to minimise environmental impacts with regulations, incentives for good environmental performance, or consumption taxes, while protecting land elsewhere for conservation,” Tanentzap said.
The researchers say that tackling the huge disparity between government subsidies and environmental incentives needs to be the first step in reducing conflict between agriculture and the natural environment, something they say has traditionally been difficult to achieve because of the power behind agri-food lobbies.
They write that while governments continue to subsidise production and famers are not accountable for the costs of their actions because associated penalties are trivial, damaging the environment will remain highly financially lucrative – with devastating consequences.
However, simply removing subsidies alone fails to reduce environmental harm, and incentives for better farming practices are still required. In the paper, researchers look at the case of New Zealand, where there are no subsidies or mitigation schemes, and much of the country has been transformed into a massive dairy farm for China as a result, says Tanentzap.
“Subsidies for production date from the post-war era, when feeding a booming population was paramount. Food security is, of course, still a major issue as populations continue to rise, but there are ways to deliver this without destroying the planet,” Tanentzap said.
“If the agriculture industry is to be subsidised, then paying farmers to protect the environment – rather than just stripping as much use from the land as possible – is something our study has shown to be effective, and something the natural world is in dire need of.”
Tanentzap AJ, Lamb A, Walker S, Farmer A (2015) Resolving Conflicts between Agriculture and the Natural Environment. PLoS Biol 13(9): e1002242. doi:10.1371/journal.pbio.1002242
First analysis of effectiveness of agri-environment schemes measured at a national level suggests that they work, but are still a drop in the ocean compared to huge government subsidies received by farming industries for environmentally damaging practices.
Tom Evans awarded the John Ray Science Prize 2015
From Department of Zoology. Published on Sep 01, 2015.
M is for Midge
By amb206 from University of Cambridge - Department of Zoology. Published on Aug 26, 2015.
Dr Henry Disney (Department of Zoology) has been fascinated by insects since he was four years old. His career has taken him all over the world. Despite losing 75% of his sight in 2012, Disney walks every day to his lab, where use of the latest imaging and magnifying technology enables him to continue his research. Below, Disney answers questions about the tiny insects that can, during summer months, turn a camping holiday on the beautiful west coast of Scotland into a nightmare.
What are midges?
Midges are classified as Diptera – which comes from the Greek for two wings. Diptera fall into three main groups: higher flies, middle flies and lower flies. Midges, like mosquitoes, fall into the lower group, which are the most ancient. They are typified by long antennae which have many segments. Some Diptera are enormously important as a threat to human health: they include many species in which the females suck blood and, in many parts of the world, transmit diseases such as yellow fever and malaria.
What is the life cycle of a midge?
The speed at which midges reproduce is temperature dependent. In the UK, you might get two or three generations a year. In the hot and steamy environment of Cameroon, where I’ve worked as a medical entomologist, you might see a new generation emerging every three weeks. Adult females lay their eggs in the water or on the margins of water. The eggs hatch into free-living larvae which go through several moults before they pupate. The adult emerges and sits on its empty case for a moment to open its wings before buzzing off.
When are midges most visible?
Midges are easiest to spot when groups of them dance in mid-air. What you’re seeing are the males saying to the females: here we are, where are you? They give off a signal that's partly smell and partly sound. If you watch really carefully, you might see a pair of midges dropping out of the group to mate. Midges swarm near an object such as a branch which gives them a point of reference. Sometimes they gather in such numbers that they make huge towers. So many midges once swarmed on Salisbury Cathedral that the fire brigade was called; it looked as if the spire was swathed in smoke.
How many species of midge are there?
In the UK, alone there are more than 500 species of non-biting midges and more than 150 species of biting midges. Identification of the species is primarily based on details of the male genitalia examined under a microscope. Increasingly this is supplemented by the use of DNA ‘barcodes’.
Why do midges bite?
Only the females bite. They need a protein-rich meal of fresh blood in order to mature their eggs. Both the males and the females rely on sugar meals for energy for flight but the females need more than this to ensure the next generation. Female midges feed on the blood of birds as well as mammals. Each species has its own preferred choice of host.
What is the midge's place in the ecosystem?
Meniscus midges live at the point where air and water meet – a zone known as the surface film. It’s a habitat that supports a whole community of plants and animals, many of them still unexplored. Some minute organisms spend their lives within the surface film; others, like meniscus midges, spend their larval lives feeding on it.
The boundary where air and water connect is rich in resources. The larvae of non-biting midges feed on algae and bacteria, filtering micro-organisms out of the water, but some are predators. The larvae of phantom midges live in the open water and prey on water fleas and small larvae. Adult midges are eaten by all kinds of things - from spiders to swallows. The larvae are eaten by fish, dragonfly larvae, water beetles and other predators.
What can midges tell us about the environment?
The apparent boundary between air and water of ponds and other bodies of water is masked by a layer of lipoprotein leached from organic materials. Within this ‘membrane’ live all kinds of microorganisms – bacteria and so on. Some of it drops in from above and some of it rises up from below. Hundreds of species depend on the ‘membrane’ for food as well as on the prey that inhabits it. Changes to the structure and content of this membrane will affect all these species.
Research has shown that midges are some of the most sensitive indicators of pollution in water. The presence of some species is a sign of a healthy water course with normal oxygen levels; their absence is a sign of lower oxygen levels and can point to pollution. Water authorities sample the numbers and species of midges present in a water course above and below a discharge – for example from a sewage treatment plant – to monitor contamination of the water by organic matter.
Oil, and detergents used to disperse oil, also alter the character of the surface layer – and will have a negative effect on species such as meniscus midge larvae that depend on this delicately balanced habitat.
What more is there to learn about midges?
Some insects have economic and medical importance. For example, there's a huge body of literature devoted to mosquitoes. Anything that bites and transmits disease is likely to attract research funding. A Scandinavian team showed that midge bites could lead to a mild fever but its effects were short-lived and quickly alleviated. Although midges are known as ‘Scotland's secret weapon’, there is no need to worry about being bitten leading to serious problems. However, biting midges have been implicated in transmitting a disease of livestock. In hot climates, midges are known to spread both African Horse Sickness and Blue Tongue virus.
There is still much to learn about midges and novel biological methods of control, that avoid the use of pesticides, for those species posing problems.
How did you get interested in insects?
I was always fascinated by natural history. When I was around four, I disappeared and everyone was out looking for me. I was found sitting among some cabbages watching a caterpillar. An aunt hugely encouraged me and left me a small legacy with which I bought my first microscope. I'm still using it more some 50 years later. My career has been immensely varied - I've worked in medical entomology in Belize and Cameroon. Since my move to Cambridge, I’m occasionally asked to report on specimens from forensic cases - including some involving infamous crimes – as well as pest problems and medical cases. I’ve authored, and contributed to, several books and written hundreds of papers. I’m never bored.
The most important question of all: how do you keep midges at bay if you have to work in areas where they are rife?
The most effective solution for people working outdoors is to wear a loose net over-garment with a hood, impregnated with DEET, over one's normal clothing. This lasts longer than applying DEET to one's skin or normal clothing. We used to test these against alternatives when running the annual field course at my field centre in Yorkshire for the London School of Hygiene and Tropical Medicine.
Next in the Cambridge Animal Alphabet: N is for an animal that won't win any beauty contests, but can live for 30 years and may be able to help in the development of new therapies for chronic pain.
Have you missed the series so far? Catch up on Medium here.
Inset images: Adult Dixella in side view (from British Dixidae (Meniscus Midges) and Thaumaleidae (Trickle Midges) by Henry Disney, published by the Freshwater Biological Association); Dorsal view of adult Dixa BM, BL, median and lateral bands on the scutum (from British Dixidae (Meniscus Midges) and Thaumaleidae (Trickle Midges) by Henry Disney, published by the Freshwater Biological Association).
Home page banner image: A chironomid midge. Credit: S Rae
The Cambridge Animal Alphabet series celebrates Cambridge's connections with animals through literature, art, science and society. Here, M is for Midge as we talk to eminent ecologist Dr Henry Disney about his lifelong interest in Diptera.
Claire Feniuk successful at 2015 International Conference on Conservation Biology in Montpellier
From Department of Zoology. Published on Aug 13, 2015.
Predators might not be dazzled by stripes
By fpjl2 from University of Cambridge - Department of Zoology. Published on Aug 12, 2015.
Stripes might not offer protection for animals living in groups, such as zebra, as previously thought, according to research published today in the journal Frontiers in Zoology.
Humans playing a computer game captured striped targets more easily than uniform grey targets when multiple targets were present. The finding runs counter to assumptions that stripes evolved to make it difficult to capture animals moving in a group.
“We found that when targets are presented individually, horizontally striped targets are more easily captured than targets with vertical or diagonal stripes. Surprisingly, we also found no benefit of stripes when multiple targets were presented at once, despite the prediction that stripes should be particularly effective in a group scenario,” said Anna Hughes, a researcher in the Sensory Evolution and Ecology group and the Department of Physiology, Development and Neuroscience.
“This could be due to how different stripe orientations interact with motion perception, where an incorrect reading of a target’s speed helps the predator to catch its prey.”
Stripes, zigzags and high contrast markings make animals highly conspicuous, which you might think would make them more visible to a predator. Researchers have wondered if movement is important in explaining why these patterns have evolved. Striking patterns may confuse predators and reduce the chance of attack or capture. In a concept termed ‘motion dazzle’, where high contrast patterns cause predators to misperceive the speed and direction of the moving animal. It was suggested that motion dazzle might be strongest in groups, such as a herd of zebra.
‘Motion dazzle’ is a reference to a type of camouflage used on ships in World Wars One and Two, where ships were patterned in geometric shapes in contrasting colours. Rather than concealing ships, this dazzle camouflage was believed to make it difficult to estimate a target's range, speed and heading.
A total of 60 human participants played a game to test whether stripes influenced their perception of moving targets. They performed a touch screen task in which they attempted to ‘catch’ moving targets - both when only one target was present on screen and when there were several targets present at once.
When single targets were present, horizontal striped targets were easier to capture than any other target, including uniform colour, or vertical or diagonal stripes. However, when multiple targets were present, all striped targets, irrespective of the orientation, were captured more easily than uniform grey targets.
“Motion may just be one aspect in a larger picture. Different orientations of stripe patterning may have evolved for different purposes. The evolution of pattern types is complex, for which there isn’t one over-ruling factor, but a multitude of possibilities,” said Hughes.
“More work is needed to establish the value and ecological relevance of ‘motion dazzle’. Now we need to consider whether colour, stripe width and spatial patterning, and a predator’s visual system could be important factors for animals to avoid capture.”
Anna Hughes has written a blog post on this research for the journal publisher BioMed Central. Above story adapted from a BioMed Central press release.
New research using computer games suggests that stripes might not offer the ‘motion dazzle’ protection thought to have evolved in animals such as Zebra and consequently inspired ship camouflage during both World Wars.
Hugh Cott - master of camouflage
From Department of Zoology. Published on Aug 11, 2015.
Close-up film shows for the first time how ants use ‘combs’ and ‘brushes’ to keep their antennae clean
By jeh98 from University of Cambridge - Department of Zoology. Published on Jul 27, 2015.
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. The 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.
“The 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).
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.
Stressed young birds stop learning from their parents and turn to wider flock
By fpjl2 from University of Cambridge - Department of Zoology. Published on Jul 23, 2015.
Highly-social zebra finches learn foraging skills from their parents. However, new research has found that when juvenile finches are exposed to elevated stress hormones just after hatching, they will later switch strategies and learn only from unrelated adult birds – ignoring their parents’ way of doing things and instead gaining foraging skills from the wider network of other adult finches.
Researchers say that spikes in stress during early development may act as a cue that their parents are doing something wrong, triggering the young birds to switch their social learning strategy and disregard parental approaches in favour of acquiring skills exclusively from other birds in the flock.
This stress cue and subsequent behavioural change would then allow the juveniles to bypass a “potentially maladaptive source of information” – possibly the result of low-quality parental investment or food scarcity at birth – and consequently avoid a “bad start in life”, say the researchers.
The changes this stress could create in the patterns of individuals' social interactions may impact important population-wide processes, such as migration efficiency and the establishment of animal culture, they say. The new study is published today in the journal Current Biology.
“These results support the theory that developmental stress may be used as an informative cue about an individual’s environment. If so, it may enable juveniles to avoid becoming trapped in a negative feedback loop provided by a bad start in life – by programming them to adopt alternative, and potentially more adaptive, behaviours that change their developmental trajectories,” said Dr Neeltje Boogert, from Cambridge University’s Department of Zoology, who authored the study with colleagues from the universities of Oxford and St Andrews.
For the study, the research team took 13 broods of zebra finch hatchlings and fed half of the chicks in each brood with physiologically relevant levels of the stress hormone corticosterone dissolved in peanut oil, and the other half – their control siblings – with just plain peanut oil. The chicks were treated each day for 16 days from the ages of 12 days old.
Once the chicks reached nutritional independence, they were released with their families into one of two free-flying aviaries, where researchers tracked their social foraging networks using radio tags called PIT tags (Passive Integrated Transponder), about the size of a grain of rice. Each bird's unique PIT tag was scanned when a bird visited a feeder, allowing the researchers to track exactly who was foraging where, when and with whom.
Using these feeder visit data, the researchers were able to build finch social foraging networks, as the thirteen zebra finch families in the two aviaries foraged and interacted over the course of 40 days.
They found that the juveniles administered with the stress hormone were less likely to spend time with their parents, spent more time with other unrelated birds and were far less choosy about which birds they foraged with; whereas the control group stuck more closely to their parents, and foraged more consistently with the same flock mates.
To test whether these stress-hormone induced differences in social network positions affected who learned from whom, Boogert devised a food puzzle for the birds, and recorded exactly when each bird started solving it.
In the new test, the birds had to learn to flip the lids from the top of a grid of holes to reach the food reward of spinach underneath. All other feeders were removed from the aviaries, and the researchers filmed a series of nine one-hour trials over three days, monitoring and scoring how each bird learned to get to the bait.
They found that, while the control group of juvenile finches did also learn from some unrelated adults, they mostly copied their parents to find out how to get the spinach. In sharp contrast, the developmentally-stressed chicks exclusively copied unrelated adults instead – not one looked to a parent to figure out the key to the spinach puzzle.
In fact, the stressed juveniles actually solved the task sooner than their control siblings, despite not using parents as role models to focus on. Boogert says this may be because they relied more on trial-and-error learning, or that they simply had access to the information sooner because they copied a large number of unrelated adult finches rather than just one of their two parents.
"If developmentally stressed birds occupy more central network positions and follow many others around, this might make them especially efficient spreaders of disease, as stressed individuals are also likely to have weakened immune systems," said Boogert.
"The next step is to explore the implications of our results for important population-level processes, such as the spread of avian pox or flu."
Inset image: Zebra finches in the ‘food puzzle’ experiment. Credit: Dr Neeltje Boogert
Juvenile zebra finches that experience high stress levels will ignore how their own parents forage and instead learn such skills from other, unrelated adults. This may help young birds avoid inheriting a poor skillset from parents – the likely natural cause of their stress – and becoming trapped by a “bad start in life”.
Isabel Palacios helps African universities reap fruits of fly research
From Department of Zoology. Published on Jul 10, 2015.
Why insects are marvels of engineering
From Department of Zoology. Published on Jul 03, 2015.
Emeritus Professor Sir Pat Bateson awarded the ZSL Frink Medal 2014
From Department of Zoology. Published on Jun 25, 2015.
Richard Preece and Roz Wade on 'Wildlife Wednesday'
From Department of Zoology. Published on Jun 18, 2015.
Prof. Simon Laughlin publishes new book on brain design
From Department of Zoology. Published on Jun 15, 2015.
Nick Davies appears on 'Springwatch'
From Department of Zoology. Published on Jun 12, 2015.
Janet Moore Prize for Supervising in Zoology
From Department of Zoology. Published on Jun 12, 2015.
All Museum creatures great and small
From Department of Zoology. Published on Jun 09, 2015.
Henry Disney paper chosen as Science Editor's Choice
From Department of Zoology. Published on May 18, 2015.
Legs give moths a flying start
From Department of Zoology. Published on May 01, 2015.
The Arup Building is renamed The David Attenborough Building
From Department of Zoology. Published on Apr 22, 2015.
Wendy Gu wins first place in BSCB BSDB Student Poster prize competition
From Department of Zoology. Published on Apr 15, 2015.
Red Noses in Zoology
From Department of Zoology. Published on Mar 25, 2015.
Zoology student success in 2015 Graduate School Life Sciences Poster and Image Competitions
From Department of Zoology. Published on Mar 25, 2015.
MPhil student wins bursary
From Department of Zoology. Published on Mar 09, 2015.
Nick Davies’ new book, Cuckoo: Cheating By Nature
From Department of Zoology. Published on Mar 06, 2015.
Museum of Zoology plans boosted
From Department of Zoology. Published on Mar 02, 2015.
Congratulations to Nick Crumpton and Robert Brocklehurst
From Department of Zoology. Published on Feb 26, 2015.
Museum of Zoology on BBC Look East
From Department of Zoology. Published on Feb 20, 2015.
Ants prefer to pick on ants their own size
From Department of Zoology. Published on Feb 11, 2015.
Graduate student discovers new species of dragonfly in Sabah, Malaysian Borneo
From Department of Zoology. Published on Jan 30, 2015.
Zoology staff feature on TV and radio
From Department of Zoology. Published on Jan 26, 2015.
'Going for Gold' with Professor Tom Welton
From Department of Zoology. Published on Jan 21, 2015.
Cambridge Biotomography Centre officially open
From Department of Zoology. Published on Jan 20, 2015.
Julian Jacobs wins Employee Recognition Award
From Department of Zoology. Published on Dec 22, 2014.
The Janet Moore Prize for supervising in Zoology
From Department of Zoology. Published on Nov 24, 2014.