February 21st, 2013 by James Ayre
Bumblebees and other pollinators are able to locate and distinguish the individual electric signals given off by flowers, new research from the University of Bristol has found. The flowers’ use of electric signals to communicate with potential pollinators is a surprise to many researchers, adding to their already impressive visual, ultraviolet, and fragrant advertising methods.
The new research is the first to show that pollinators make use of electrical signals for navigation and the pursuit of food. During new research, scientists at Bristol’s School of Biological Sciences found that flowers release varying patterns of electrical signals that are capable of communicating specific information to insect pollinators. The electrical signals likely work in conjunction with other communication tools, such as visual patterns, smells, and ultraviolet markings, to communicate with pollinators.
“Plants are usually charged negatively and emit weak electric fields. On their side, bees acquire a positive charge as they fly through the air. No spark is produced as a charged bee approaches a charged flower, but a small electric force builds up that can potentially convey information.”
For the new research, electrodes were implanted into the stems of petunias, and it was observed that as a bee lands on a flower, “the flowers’ potential changes and remains so for several minutes. Could this be a way by which flowers tell bees another bee has recently been visiting? To their surprise, the researchers discovered that bumblebees can detect and distinguish between different floral electric fields.”
This was further explored by giving the bees ‘a learning test’. The test showed that when electric signals were present in conjunction with colors, the bees were much faster at ‘learning’ to distinguish between the colors.
It’s not entirely clear yet how the bees actually detect the electric fields. Currently the researchers are speculating that the rather hairy bodies of bumblebees aid in the detection. Similar to when static electricity makes your hair stand on end.
“The discovery of such electric detection has opened up a whole new understanding of insect perception and flower communication.”
Dr Heather Whitney, one of the co-authors of the study, said: “This novel communication channel reveals how flowers can potentially inform their pollinators about the honest status of their precious nectar and pollen reserves.”
Professor Daniel Robert said: “The last thing a flower wants is to attract a bee and then fail to provide nectar: a lesson in honest advertising since bees are good learners and would soon lose interest in such an unrewarding flower.
“The co-evolution between flowers and bees has a long and beneficial history, so perhaps it’s not entirely surprising that we are still discovering today how remarkably sophisticated their communication is.”
The research was just published February 21st in the journal Science Express.
Some more information on Bumblebees and pollinator/flower relations:
“Bumblebees are social insects that are characterised by black and yellow body hairs, often in bands. However, some species have orange or red on their bodies, or may be entirely black. Another obvious (but not unique) characteristic is the soft nature of the hair (long, branched setae), called pile, that covers their entire body, making them appear and feel fuzzy. They are best distinguished from similarly large, fuzzy bees by the form of the female hind leg, which is modified to form a corbicula: a shiny concave surface that is bare, but surrounded by a fringe of hairs used to transport pollen (in similar bees, the hind leg is completely hairy, and pollen grains are wedged into the hairs for transport).”
“Like their relatives the honey bees, bumblebees feed on nectar and gather pollen to feed their young.”
“Bumblebees generally visit flowers exhibiting the bee pollination syndrome. They can visit patches of flowers up to 1–2 kilometres from their colony. Bumblebees will also tend to visit the same patches of flowers every day, as long as they continue to find nectar and pollen, a habit known as pollinator or flower constancy. While foraging, bumblebees can reach ground speeds of up to 15 metres per second (54 km/h).”
“Experiments have shown that bumblebees can use a combination of colour and spatial relationships to learn which flowers to forage from. After arriving at a flower, they extract nectar using their long tongue (‘glossa’) and store it in their crop. Many species of bumblebee also exhibit what is known as “nectar robbing”: instead of inserting the mouthparts into the flower normally, these bees bite directly through the base of the corolla to extract nectar, avoiding pollen transfer. These bees obtain pollen from other species of flowers that they ‘legitimately’ visit.”
“Pollen is removed from flowers deliberately or incidentally by bumblebees. Incidental removal occurs when bumblebees come in contact with the anthers of a flower while collecting nectar. The bumblebee’s body hairs receive a dusting of pollen from the anthers, which is then groomed into the corbicula (‘pollen basket’). Bumblebees are also capable of buzz pollination.”
“In at least a few species, once a bumblebee has visited a flower, it leaves a scent mark on the flower. This scent mark deters visitation of the flower by other bumblebees until the scent degrades. It has been shown that this scent mark is a general chemical bouquet that bumblebees leave behind in different locations (e.g. nest, neutral, and food sites), and they learn to use this bouquet to identify both rewarding and unrewarding flowers. In addition, bumblebees rely on this chemical bouquet more when the flower has a high handling time (i.e. it takes a longer time for the bee to find the nectar).”
“Once they have collected nectar and pollen, bumblebees return to the nest and deposit the harvested nectar and pollen into brood cells, or into wax cells for storage. Unlike honey bees, bumblebees only store a few days’ worth of food and so are much more vulnerable to food shortages.”
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