Tag Archives: insect

Miles From Home: How Ants can Navigate Long Distances (and back!) to Forage

Ants are well known for their extraordinary ability to find food, and bring back enough to feed their vast social organisations. Being able to form relationships with other organisms that digest food, carry objects 50 times their weight and achieve great feats of communication and learning all help them forage… but how exactly do they find their way? Recent research from the University of Edinburgh has concluded the fascinating story of how the Formicidae navigate.

Plot a Course! Direction of Travel

Ants can decide on a direction for walking by using the position of the Sun in their visual field, as specialised cells in their compound eyes can detect the UV polarised light emitted by the Sun. Ants can maintain the correct course, whilst decoupling information where their body is an which direction they are travelling in. They also make use of visual landmarks (such as leaf litter), olfactory and tactile cues, and some species use the Earth’s magnetic field for navigation. According to the researchers at the University of Edinburgh, the ants construct a more sophisticated representation than they thought possible from the small size of their ganglia (brains), and can integrate information from different modalities (and from different areas of the brain) into the representation of direction.

How Far? Keeping track of Distance

Day-foraging ants, such as those in the genus Cataglyphis, are able to navigate exceptionally long distance (up to 200 metres and back!) by recording the distance they have travelled as well as the direction. An internal pedometer helps the ant remember the number of steps taken and this information is integrated with the ‘optical flow’ of objects moving around their visual field (which is an illusion- of course it is actually the ant that moves). Rather than each ant randomly roving away from the hive in search of food, the successful ‘pioneer’ must communicate the location to her sisters so they can make a sortie to the high quality patch of forage en masse…

neivamyrmex_army_ants_raiding_trail.jpg

Follow the Leader: Scent Trails

The long line of ants that you are bound to see in tropical forests are formed from scent trails that allow them to navigate back home, even if it is 200 metres away and in the dark! The ability to find the shortest route back is a crucial adaptation for avoiding desiccation in hot and arid environments. However, in army ant species, a group of foragers who become separated from the main marching column can turn back and form a circular ant mill, and run round constantly until they die of exhaustion! Ants have also been recorded to carry each other along a route, if an older and more experience forager notices that an internal nest worker (which are less familiar with the outdoor environment) is off the trail.

Final Word

So ants are able to backtrack to the location of their nest using their memories and the Sun as a reference point, and the way they operate is very similar to a self-driving car. This new research gives a unique insight into how brains of ants (and other insects) operate, and will inspire the next developments in robot system building to mimic their functioning, which would especially be useful for robots that need to navigate in forested areas. Modelling the neural circuits in the ant brain will also be useful to simply understanding more about the complex behaviours of the fascinating family of insects.

Further Reading

http://www.cell.com/current-biology/fulltext/S0960-9822(16)31466-X

http://jeb.biologists.org/content/209/1/26

http://science.sciencemag.org/content/353/6304/1155

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Bees: How do they Combat Disease?

A honeybee hive sick with disease can spell the end of a colony. Recent research has shown bees can use vaccinations and nurse one another to protect themselves from and prevent certain diseases. But how exactly do they do it?

Vaccinations

Honeybees live in huge colonies that co-operatively rear brood (developing eggs and larvae), so must find some way of protecting the next generation against disease. To do this, the workers actually naturally immunize their young against certain diseases which they might encounter. The findings of a recent paper, published in the journal PLOS Pathogens, finally reveal how the important immune-signal protein vitellogenin works to do this.

It was found foraging workers pick up and bring back contaminated pollen and nectar to the hive, and workers create royal jelly using it. The bacteria picked up from the environment persists in the jelly, and is then fed exclusively to the queen. The pathogens are digested in the queen’s gut and stored in the queen’s fat body (an organ similar to a liver). Fragments of the bacteria are then ‘carried’ by vitellogenin, taken via the blood to developing eggs inside the queen. These young are now immunized, all without taking a step outside their hexagonal brood cell.

Now that we know how bees immunize their young against infection, scientists can work on synthesizing a vaccine to prevent commercial bee colonies from becoming infected with disease- possibly aiding the fight against the crisis of colony collapse disorder (CCD).

But not all diseases in bees can be fought with immunity inherited from a parent. So how else do honeybees fight infection?

Nursing

Much like communist societies, honeybee hives divide up the hugely varied workload between different ‘castes’ of the colony (workers, drones and queen), and further divide workers into roles based on their size and age. Older, more experienced workers may be more likely to forage for the colony, and act as guard bees (they have actually been found to patrol the entrance the hive!). Younger, more naive workers however are usually more suited to nursing duties, which include feeding and tending to the queen and brood, as well as medical specialists which provide sick workers with anti-biotic laced honey.

A recent study, published in Behavioural Ecology and Sociobiology, gave nurse bees infected with a Nosema ceranae parasite a choice of honey from different plants. Bees with a higher level of infection tended to eat more sunflower honey, which contains the most antimicrobial activity. It also reduced the level of infection in the bees by 7%. A separate study suggests different honeys are effective against different diseases the bees may encounter. For example linden honey was better at fighter off a an infection of European foulbrood whereas sunflower honey was more effective against American foulbrood.

Nurse bees have other medical roles to reduce infection in a hive. For example, they can act as undertakers and remove the corpses of dead bees from the colony, dumping them far from the entrance. This behaviour is used to avoid spreading infections from pathogens and entomopathogenic fungi that proliferate on the bodies of dying insects,

In both of these incredible behaviours, bees can vaccinate and immunize their brood and sister workers by means of medicinal honey and food contaminated with bacteria. But where do these come from in the first place?

Natural Remedies

Floral nectar typically contains plant secondary compounds (those used for defence by the plant) which possess antimicrobial properties. This can be very useful to bees. Before the publishing of a recent study in PLoS One, we knew little more than the fact pollinators can reduce their parasite load by consuming nectar containing compounds such as nicotine.

This recent research has indicated parasitized bumblebees are taking advantage of these plant secondary metabolites in the wild, such as iridoid glycosides, and have a strong preference for visiting flowers that possess them. This quality of bees to self-medicate, by altering their foraging behaviour whilst parasitized, has massive implications for their ability to fight disease

Honeybees have other sources of medicine besides anti-microbial nectar. They have been found to collect resin from plants and incorporate it into their nests, which may help stop fungal parasities from colonizing their hive. (A study showed bees collect more of the resin when infected with fungal spores)

Final word

The fact that honeybees and bumblebees have evolved so many different ways in which to fight disease implies the risk that our wild pollinators face, as well as just how long they have been co-evolving alongside their assailing antagonists. Climate change and other drivers have recently made the problem of disease much worse, and research into this need to be rapid if we are to help our plighted pollinators.

Further Reading

Erler, S., Denner, A., Bobiş, O., Forsgren, E., & Moritz, R. F. (2014). Diversity of honey stores and their impact on pathogenic bacteria of the honeybee, Apis mellifera. Ecology and evolution, 4(20), 3960-3967.

Gherman, B. I., Denner, A., Bobiş, O., Dezmirean, D. S., Mărghitaş, L. A., Schlüns, H., … & Erler, S. (2014). Pathogen-associated self-medication behavior in the honeybee Apis mellifera. Behavioral Ecology and Sociobiology, 68(11), 1777-1784.

Richardson, L. L., Bowers, M. D., & Irwin, R. E. (2015). Nectar chemistry mediates the behavior of parasitized bees: consequences for plant fitness.Ecology.

Salmela, H., Amdam, G. V., & Freitak, D. (2015). Transfer of immunity from mother to offspring is mediated via egg-yolk protein vitellogenin. PLoS Pathog, 11(7), e1005015.

Simone-Finstrom, M. D., & Spivak, M. (2012). Increased resin collection after parasite challenge: a case of self-medication in honey bees. PLoS One,7(3), e34601.

News Roundup: Autumn 2015.

Disease eradications, Bee vaccinations and Entomophagy- catch up on all the latest entomological news stories you might have missed!

Risks of Eating Insects


The European Food Safety Authority (EFSA) have recently published a report on using insects as a protein source for animal feed and human consumption. It found that edible insects could contain biological and chemical contaminants, depending on how the large scale insect farms were managed.

With an estimated global population of 9 billion by 2050, using insects as a high quality source of protein as feed (for chickens, for example) could give a much needed food conversion rate (lower levels of initial energy and water required). Insect meat is also a quality source of fat, fibre, minerals and vitamins.

It is estimated that insects such as flies, moths, mealworms and crickets/locust already form the diet of at least 2 billion people. There is still clearly a way to go until western cultures can adopt new foodstuffs and a better understanding of the hazards of eating insects is required for the next step.

GM Mosquitoes trial reduced Dengue by 95%

A trial where scientists released thousands of ‘friendly’ Aedes aegypti mosquitoes infected with a bacteria that will intended to suppress dengue fever has yielded positive results. The theory was that the genetically modified yellow fever carrying mosquitos breed with the existing population and become the dominant type, thus eliminating the disease spreading variants.

The results of the Oxitec trial in Brazil found that the disease carrying mosquito number were reduced by 95%, well below the disease transmission threshold. The control was species-specific, and the Oxitec male mosquitoes mate with the naturally occurring females of the population and their offspring die before they can transmit the disease.

New methods of pest control like this are crucial as Aedes aegypti is developing resistance to insecticides and removal of breeding sites leads to them re invading the following year from neighbouring habitats that are inaccessible to us. There is also no vaccine or specific medication currently for dengue, chikungunya or zika virus (3 debilitating mosquito-borne diseases) so the development of new methods is crucial.

Honeybees give each other Vaccinations

Once a disease takes hold of a hive, the workers of a honeybee colony become disorientated and fail to forage to feed their sisters and brood. Luckily bees naturally immunize their young against certain diseases found in their environment, and scientists have recently discovered how exactly they do this.

The latest research suggests that the queen is fed on royal jelly from pollen infected with bacteria, and these are digested in the gut and stored in the queen’s fat body. Pieces of the bacteria are then bound to vitellogenin (a blood protein) and this is carried via blood to supply developing eggs with immunity.

The industries relying on honeybees colonies and the pollination service could benefit if a similar vaccine was produced for other bee diseases- like american foul brood. The discovery of vitellogenin, the carrier of immune-priming signals, could have implications for other animals that pass on immunity to their young.

Wasps are an indicator for environmental decline

A decline in wasps is thought to be a reaction to the increased harm of pesticides on wasps, and their food resource. Wasps play a key role in ecosystems (a ‘keystone species’), and taking them out would cause many systems in an ecosystem to collapse- for example dead insects and detritus would accumulate, with pestilent flies possibly taking advantage of this and proliferating.

A possible decline in wasps that might go unnoticed is what’s called a ‘shifting baseline syndrome’, meaning that small declines in number each year might go unnoticed, despite a reduction in 50% of population over 20 years (for example).

For the 2 most recognizable species of social wasp, Vespula germanica and Vespula vulgaris, there have been reported losses in number and this has been attributed to a reduction in their food resources- wasps are carnivorous during colony development (eating dead insects, aphids, etc.) and take advantage of sugar foods (such as fermenting fruit) late in the season. The decline of wasps could therefore be a signal that insects lower in the food chain are vanishing too and endangering whole systems. Environmental decline should be indicated by more than just a decline in wasps, though!

Further Reading:

Entomophagy http://www.bbc.co.uk/news/science-environment-34476742

Dengue Mosquitos http://entomologytoday.org/2015/07/03/genetically-engineered-mosquitoes-reduce-population-by-95-percent/

Honeybee Immunization http://entomologytoday.org/2015/08/03/researchers-discover-key-to-bee-vaccination/

Wasps and Ecosystems http://www.independent.co.uk/voices/nature-studies-fewer-wasps-to-swat-is-a-sign-of-an-ecosystem-in-serious-trouble-a6680881.html

Cells from Insects could Create Everlasting Paint.

blue-morpho-butterfly-size-pic-1173_11

Durable, cheap and environmentally friendly paint may soon be on sale since scientists at the Natural History Museum in London have unlocked the key to paint that never fades, using unique cells from butterflies and other insects. The Blue Morpho butterfly, Morpho peleides, is just one of many insects that have transparent, iridescence wings created by small three-dimensional structures that alter the way light is reflected.

The phenomenon is created by ‘structural colouration’. The wing is made up of transparent scales that have intricate shapes, which scatter light when it hits them. This is what creates the vibrant colour that changes when looking at it from different angles. Professor Andrew Parker, Oxford University, has grown cells from butterfly wings and weevil shells that have this nano-property.

Cells dissected from the blue morpho chrysalis were used to culture an entire forewing. The team attempted to convert the cells to scales, but part of the original cell was lost, so that the cells couldn’t be used to produce more scales. This means that butterfly cells are suitable for mass production of coloured scales, but other insects like the Blue Weevil, genus Metapocyrtus, could be used instead. These weevils use a different type of cell, also found in the opal gemstone, which can be used to make any colour.

Traditional dyes and pigments fade over time, whereas paints, clothes and make-up that use structural colouration could retain their colour and vibrancy forever. Cosmetic and paint industries would require huge quantities for commercial use, which may only be achievable using the weevil cells. With a sufficient supply of nutrients and growth hormones, cells from weevils could be used to make industrial quantities of everlasting paint.

Source: Natural History Museum.