Bees under the spotlight

Recent research has uncovered a novel biopesticide which is safe for bees and doesn’t affect their food foraging ability, while another study has found that this activity might be aided by polarised light. The novel biopesticide combines a natural toxin from the venom of the Australian funnel web spider – Hv1A – with snowdrop lectin GNA – which is used as a carrier – to create an insect-specific fusion protein product. The compound has huge potential as an environmentally-benign ‘bee-safe’ biopesticide and an alternative to pesticides – linked to a decline in bee populations – say researchers from Newcastle University. Bees were fed the biopesticide in acute and chronic doses over seven days, during which the team carried out a series of memory tests. They found the compound had only a slight effect on survival and no measureable effect on their learning and memory, which play an important role in food foraging. “Our findings suggest that Hv1a/GNA is unlikely to cause any detrimental effects on honeybees,” said Professor Angharad Gatehouse from the School of Biology. “Previous studies have already shown that it is safe for higher animals, which means it has real potential as a pesticide and offers us a safe alternative to some of those currently on the market.” The biopesticide must be ingested orally by the insect for it to have any effect, rather than absorbed through the exoskeleton like many others. The toxin is a calcium channel blocker, a previously underexplored insecticidal target. “Calcium channels are linked to learning and memory in bees so it’s vital that any pesticide targeting them does not interfere with this process,” said Erich Nakasu. “Although Hv1a/GNA was carried to the brain of the honeybee, it had no effect on the insect which suggests the highly selective spider venom toxin does not interact with the calcium channels in the bee.” When foraging for food, honeybees must learn and remember floral traits associated with food – disruption to this function has profound implications for colony survival because those unable to learn with not find food or be able to return to their hives. Bumblebees use polarised light to help them navigate, but it has been discovered that they also use this ability when foraging for food. Professor Julian Partridge, Professor of Zoology from the University of Bristol, investigated whether bees could learn polarisation patterns of artificial flowers in order to obtain a food reward. Freely foraging bees were able to differentiate between a rewarding sucrose solution and adversity quinine solution given by artificial flowers with different polarisation patterns. However, the bees could only discriminate between the two flowers when they were viewed from below. Around 53% of flower species face down, so researchers believe their polarisation patterns might be presented in such a way to be visually accessible to the region of the bee’s eye which includes the polarisation sensitive Dorsal Rim Area. Light reflected from these pendant flowers has the potential to contrast with skylight polarisation – which helps bees to navigate – helping the bee to detect and identify such flowers. "Both pollinator and plant fitness is greatly dependent on the ability of pollinators to discriminate flowers accurately, and bees have been shown to be able to use a wide range of floral cues, including colour, shape, texture, certain chemical compounds and temperature, to improve the identification and recognition of flowers,” Professor Partridge said. "Recent findings have added floral humidity and electric fields as additional methods with which pollinators can discriminate flowers, and it is advantageous for a plant to produce a number of different signals that a pollinator can utilise effectively. Our findings suggest polarisation vision may provide sensory access to an additional floral cue for bees." Novel biopesticide based on a spider venom peptide shows no adverse effects of honeybees Bees learn polarisation patterns