Investigating the loss of bee colonies
Harmen Hendriksma, a doctoral student at the University of Würzburg’s Department of Animal Ecology and Tropical Biology, has developped an artificial honeycomb. (Foto: Gunnar Bartsch)
A global decline in bee numbers has been giving cause for concern for many years now. The reasons for the sudden loss of whole colonies remain unclear. Biologists from the University of Würzburg have now developed a new approach that might help shed light on this issue.
The disappearance has a name: Colony Collapse Disorder (CCD). Bee researchers from the USA first used the term in 2007 after beekeepers alerted them to the mysterious mass disappearance of their colonies. However, this sudden wipeout of bee populations did not stay confined to the USA. The phenomenon has since been observed worldwide.
Countless theories abound as to the triggers for their death. The prime suspects are parasites, such as the Varroa mite. But the increased use of pesticides in farming and dwindling biodiversity are also under the spotlight.
Difficult research on bees
The search for the culprits is a difficult one particularly because no two colonies are the same and the conditions under which the bees grow up and live are never identical. This does not represent a good basis for scientific work. But all this might be about to change: “We have developed a method that allows bees to be reared in large numbers in the laboratory,” says Harmen Hendriksma. Scientists worldwide could use this to explore the factors that make life difficult for bees under conditions that are controlled and comparable with one another.
Hendriksma is a doctoral student at the University of Würzburg’s Department of Animal Ecology and Tropical Biology. His work is reported on in the latest issue of the journal Methods in Ecology and Evolution published by the British Ecological Society.
Until now, scientists wanting to rear bees in the laboratory have first and foremost needed a steady hand and a delicate touch. They have had to use feathers, needles, and tweezers to extract bee larvae from honeycombs – which is not exactly easy to do as baby bees in the early larval stage measure no more than one millimeter and are virtually invisible to the naked eye. This work is time-consuming and dangerous – at least for the larvae. They are so sensitive that many of them do not survive the traumatic relocation or often suffer developmental problems.
The newly developed method
It is at this point that Hendriksma’s development comes into play: “We use a kind of artificial honeycomb made of plastic,” says the doctoral student. The box is roughly the same size as a cigar case and has 110 cells that resemble a typical wax honeycomb. At its ends are removable floors shaped like small dishes. It is in these that the queen lays her eggs.
The scientists then remove the dishes and carry them plus the contents to their laboratory. “Using this technique we managed to collect more than 1000 larvae within 90 minutes,” says Hendriksma. What is more, the larvae do not appear to have any problems with this method: 97 percent of them survived the transport and developed perfectly normally in the laboratory through to the larval stage just prior to pupation.
According to Hendriksma, the successful rearing of bees in the laboratory holds the key to the search for the causes of colony collapse: “Only in the laboratory is it possible to examine under controlled conditions how bee development is affected by specific factors – such as insecticides, the Varroa mite, or a poor diet.” This is in stark contrast to colonies living outside, whose lives are determined by numerous uncontrollable influences.
This technique also finally offers scientists the added advantage of being able to work under identical conditions in different locations, meaning that they can compare their findings or check each other’s results.
The economic importance of bees
Hendriksma believes it is vital to know more about bee mortality: “Bees are essential to both nature and the farming industry.” After all, they are the main natural pollinators.
The Food and Agriculture Organization of the United Nations (FAO) estimates that more than two thirds of the 100 crops in the world are pollinated primarily by honey bees. And according to a study in 2008 by scientists from France and Germany the damage that could result in future from the absence of pollinating insects would run to between 190 and 310 billion euros a year.
Out in the wild too, bee pollination is hugely significant. “Bees are important to both plants and animals.” They enable plants to reproduce and animals to feed on their fruit. The bee therefore forms “the basis for biodiversity”.
The research group
Harmen Hendriksma belongs to a research group led by Professor Ingolf Steffan-Dewenter, who became Chairman of the Department of Zoology III (Animal Ecology and Tropical Biology) at the University of Würzburg a year ago. In field and lab experiments, the group explores issues such as population dynamics, biodiversity, and species composition in insects, the interactions between plants, plant eaters, pollinators, and their adversaries, as well as the importance of insects to terrestrial ecosystems. The group also looks at the impact that human influences have on these ecosystems.
As far as bees are concerned, the scientists are researching how certain factors – the decline in biodiversity, the intensification of agricultural production, the cultivation of transgenic plants, the use of pesticides, and the spread of diseases, for example – each affect the occurrence of species individually and in different combinations.
The new method for rearing bees in the laboratory is already being used by the Würzburg scientists in a study funded by the Federal Ministry of Education and Research. Here, they are examining the effect of a new transgenic variety of maize on honey bees.
“Honey bee risk assessment: New approaches for in vitro larvae rearing and data analyses”, Harmen Pieter Hendriksma, Stephan Härtel, and Ingolf Steffan-Dewenter, Methods in Ecology and Evolution doi: 10.1111/j.2041-210X.2011.00099.x
A PDF of the publication can be obtained from the University of Würzburg’s Public Relations Office, T: +49 (0)931 31-82172, e-mail: 
presse@zv.uni-wuerzburg.de
Contact: Harmen Hendriksma, T: +49 (0)931 31-82385, e-mail: harmen-pieter.hendriksma@uni-wuerzburg.de
22.03.2011, 09:30 Uhr