Protecting Bees Using ‘Nature’s Medicine Cabinet’
For thousands of years humans have recognised the medicinal qualities of some plants but it is only recently that we have begun to appreciate how those same chemicals might affect other animals. Now a new study has examined the impact of several toxins found naturally in the nectar of different plants on parasitic infections in bees.
Plants have tried many different ways during evolutionary history to protect themselves from herbivores. Some grow spikes or serrations on their leaves but by far the most common deterrent is poison. Toxic substances, known properly as ‘secondary metabolites’, in the leaves can be a powerful weapon against grazers but many of these substances then end up in the bodies of pollinators, like bees, which feed on the plant’s nectar. Researchers from the University of Massachusetts Amherst and Dartmouth College infected 539 Eastern bumblebees (Bombus impatiens) with a common gut parasite (Crithidia bombi). In nature these parasites can dramatically shorten the lifespan of individual bees and spread very quickly. The researchers then exposed the bees to nectar which was either normal ‘control’ nectar, or else contained one of eight naturally occurring toxins. These secondary metabolites included substances like caffeine, nicotine and thymol, which is the chemical that gives thyme it distinctive flavour.
The results were dramatic. They showed that exposure to the toxins had reduced the parasite load in the bees’ guts by up to 81% when they were tested seven days later. This reduced the parasite load on the bees themselves but most significantly it reduced the chances of them passing the parasite to other bees through their faeces. This could potentially prevent the whole colony from become infected and it was this impact on transmission which was among the most significant findings of this study.
Today bee populations worldwide are under threat from disease and this study suggests a relatively easy way to make a dramatic difference. By encouraging growers and gardeners, who rely on bees for pollination, to plant certain types of flowering plants it might be possible to partially protect bees against parasitic infection by giving them access to what the researchers termed ‘nature’s medicine cabinet’. Although there is no evidence that bees themselves actively seek out these medicinal plants, simply increasing their exposure to them may be enough to significantly improve their resistance to disease. There is also no reason to suspect that only bees will benefit as many pollinating insects are affected by similar parasites.
Richardson, L.L., et al. 2015. Secondary metabolites in floral nectar reduce parasite infections in bumblebees. Proceedings of the Royal Society B. DOI: 10.1098/rspb.2014.2471.
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