06 | February | 2019 | Kevin's Walk on the Wild Side

File 20190204 193220 127qf8i.jpg?ixlib=rb 1.1 — To help draw bees’ attention, flowers that are pollinated by bees have typically evolved to send very strong colour signals.
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Adrian Dyer, RMIT University and Tanya Latty, University of Sydney

Walking through our gardens in Australia, we may not realise that buzzing around us is one of our greatest natural resources. Bees are responsible for pollinating about a third of food for human consumption, and data on crop production suggests that bees contribute more than US$235 billion to the global economy each year.

By pollinating native and non-native plants, including many ornamental species, honeybees and Australian native bees also play an essential role in creating healthy communities – from urban parks to backyard gardens.

Despite their importance to human and environmental health, it is amazing how little we know how about our hard working insect friends actually see the world.

By learning how bees see and make decisions, it’s possible to improve our understanding of how best to work with bees to manage our essential resources.

Insects in the city: a honeybee forages in the heart of Sydney.
Adrian Dyer/RMIT University

How bee vision differs from human vision

A new documentary on ABC TV, The Great Australian Bee Challenge, is teaching everyday Australians all about bees. In it, we conducted an experiment to demonstrate how bees use their amazing eyes to find complex shapes in flowers, or even human faces.

Humans use the lens in our eye to focus light onto our retina, resulting in a sharp image. By contrast, insects like bees use a compound eye that is made up of many light-guiding tubes called ommatidia.

The top of each ommatidia is called a facet. In each of a bees’ two compound eyes, there are about 5000 different ommatidia, each funnelling part of the scene towards specialised sensors to enable visual perception by the bee brain.

How we see fine detail with our eyes, and how a bee eye camera views the same information at a distance of about 15cm.
Sue Williams and Adrian Dyer/RMIT University

Since each ommatidia carries limited information about a scene due to the physics of light, the resulting composite image is relatively “grainy” compared to human vision. The problem of reduced visual sharpness poses a challenge for bees trying to find flowers at a distance.

To help draw bees’ attention, flowers that are pollinated by bees have typically evolved to send very strong colour signals. We may find them beautiful, but flowers haven’t evolved for our eyes. In fact, the strongest signals appeal to a bee’s ability to perceive mixtures of ultraviolet, blue and green light.

Yellow flower (Gelsemium sempervirens) as it appears to our eye, as taken through a UV sensitive camera, and how it likely appears to a bee.
Sue Williams and Adrian Dyer/RMIT University

Building a bee eye camera

Despite all of our research, it can still be hard to imagine how a bee sees.

So to help people (including ourselves) visualise what the world looks like to a bee, we built a special, bio-inspired “bee-eye” camera that mimics the optical principles of the bee compound eye by using about 5000 drinking straws. Each straw views just one part of a scene, but the array of straws allows all parts of the scene to be projected onto a piece of tracing paper.

How a bee eye camera works by only passing the constructive rays of light to form an image.
Sue Williams and Adrian Dyer/RMIT University

The resulting image can then be captured using a digital camera. This project can be constructed by school age children, and easily be assembled multiple times to enable insights into how bees see our world.

Because bees can be trained to learn visual targets, we know that our device does a good job of mimicking a bees visual acuity.

Student projects can explore the interesting nexus between science, photography and art to show how bees see different things, like carrots – which are an important part of our diet and which require bees for the efficient production of seeds.

Clip from “The Great Australian Bee Challenge, Episode 2.

Understanding bee vision helps us protect bees

Bees need flowers to live, and we need bees to pollinate our crops. Understanding bee vision can help us better support our buzzy friends and the critical pollination services they provide.

In nature, it appears that flowers often bloom in communities, using combined cues like colour and scent to help important pollinators find the area with the best resources.

Having lots of flowers blooming together attracts pollinators in much the same way that boxing day sales attract consumers to a shopping centre. Shops are better together, even though they are in competition – the same may be true for flowers!

This suggests that there is unlikely to be one flower that is “best” for bees. The solution for better supporting bees is to incorporate as many flowers as possible – both native and non native – in the environment. Basically: if you plant it, they will come.

We are only starting to understand how bees see and perceive our shared world – including art styles – and the more we know, the better we can protect and encourage our essential insect partners.

Looking at the fruits and vegetables of bee pollination; a bee camera eye view of carrots.
Sue Williams and Adrian Dyer/RMIT University

Adrian Dyer, Associate Professor, RMIT University and Tanya Latty, Senior Lecturer, School of Life and Environmental Sciences, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

File 20190201 112314 r476de.png?ixlib=rb 1.1 — The Conversation

Bronwyn Smithies, The University of Queensland and Edward Kalani Gilding, The University of Queensland

Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.

If you are observant enough in the Australian bush, you may be able to spot the spade flower, a member of the violet family. Spade flowers grow under the semi-shade of open eucalypt forest, among other little green herbaceous plants.

This often-overlooked member of Australian flora hides some interesting secrets, including a rare chemical that may hold the key to turning regular plants into medicinal cures.

The common name spade flower refers to the flower’s shape, which is dominated by the spade-shaped labellum. Its botanical name, Hybanthus enneaspermus, is equally descriptive. The generic name Hybanthus means “humpbacked flower”, referring to the posture of the flowers. Meanwhile, the specific name enneaspermus means “nine-seeded”, because upon maturity each tiny 5mm fruit splits into three sections bearing three seeds each.

A hidden talent

Violets are familiar objects, from the showy native Viola banksii or the scent of European sweet violets. What is not common knowledge is that members of the Violaceae family produce some very curious molecules called peptides.

People – and many other organisms – use peptides as signals that enable communication between cells and tissues. An example of a peptide messenger from humans with an important function is oxytocin, also known as the “love hormone”. Oxytocin regulates social bonding and other key aspects of our biology and sociality. In contrast, plants sometimes use peptides for a different purpose, as toxins to protect themselves from insects and other pests.

But unlike most peptides, those produced by Violaceae are circular instead of linear. Because of this circular shape, they are highly stable in conditions that would degrade other peptides. This special class of peptides are called “cyclotides” and are only found in relatively few plant species. This is why we have been searching all across northern Australia, from the Kimberley region in Western Australia to the Queensland coast, for samples of native Australian Violaceae.

The first cyclotide to grab the attention of scientists comes from an African plant called kalata-kalata, traditionally used in teas to hasten childbirth. In 2013, it was shown that a specific cyclotide from kalata-kalata acts on smooth muscle to cause contraction of muscle tissue.

Kalata-kalata, or *Oldenlandia affinis*, is used in a traditional medicinal tea. It’s efficacy comes from the cyclotides it produces.
KalataB1/Wikipedia

But easing childbirth might not be the only effect cyclotides have. Initial experiments with spade flower extracts demonstrate a significant effect on the mating behaviour of rats. Rats treated with peptide-laden extracts from spade flower exhibit, uh, increased copulation frequency.

In us humans, the receptors that detect peptides control libido, sleep, and other aspects of our biology. These observations leave spade flower cyclotides as prime suspects underpinning this amorous bioactivity, and could be the basis for coining yet another name for this plant: the “love shrub”.

Despite this intriguing effect, until further scientific investigation validates these initial aphrodisiac findings and their basis, it is probably wise to steer clear of ingesting these plants.

Spade flower is indigenous to Australia, but the native range extends through southern Asia, India, and into Africa. Despite the wide range of the species, the plant is usually distributed in a here-and-there fashion. In our experience this sparse distribution has meant finding no sign of them along the roughly 600km Gibb River Road at the end of the wet season, and just a single observation from a roadside south of Gladstone. This scarcity tests the resolve of many skillful plant spotters, ourselves included.

Spade flower buds are delicate and graceful.
Author provided

You’re most likely to find spade flowers in semi-shaded environments north of the Queensland-New South Wales border, along the east coast, and across the Top End. It grows along roadsides or near waterways, but it is difficult to spot because its narrow leaves tend to blend into the mix of herbs growing alongside it.

Look for the lilac spade-shaped flowers among the understory herbs during the warmer and wetter months, but do this before midday when the flowers wilt away from view.

There are other Hybanthus species in Australia, however the genus appears to be polyphyletic (meaning they are grouped together but don’t share a single common ancestor) so the genus is not truly representative of a single taxonomic group per se. Other Hybanthus species look similar to spade flower, namely H. monopetalus, which grows multiple purple-blue flowers on a single stem instead of single lilac-coloured flowers.

In habitats between Brisbane and Sydney spade flower is scarce, however a similar and arguably showier species called H. stellarioides occurs. H. stellarioides is somewhat more delicate, but what really sets it apart are the bright royal orange flowers it produces in summer and autumn.

Spade flowers next to their flashier orange cousin, *H. stellarioides*.
Author provided

In many other aspects these two species look so similar that for some time H. stellarioides was considered a subspecies of the spade flower, however it is now clear they are genetically distinct.

As part of Professor David Craik’s research group at The University of Queensland, we have sequenced the expressed genes of spade flower shoots and roots to uncover how these clever plants make cyclotides. These data helped explain spade flower’s cyclotide amino acid sequences.

Armed with this information, the scientific community can now make stable designer peptides as potential pharmaceuticals. The Craik group is working on making modified cyclotides that can treat cancer and other diseases, and then reintroducing those genes into edible plants – turning a regular tomato plant into a medicinal plant for example. Learning how the spade flower makes cyclotides has already helped us to make some new cyclotides in other plant seeds.

Finally, this work facilitates the isolation of individual “love shrub” cyclotides to test their effects. Watch this space and the herbs underfoot. The humble and shy spade flower may have more surprises yet!