Monday, 2 April 2012

Thrill Seeking Bees and Brain Gene Expression

Last year, a team of researchers studied the behaviour of the honeybee, Apis mellifera.  While most worker bees collect pollen and nectar from known sources, the scouts play a very important role in the colony’s survival. Only some bees ever exhibit this behaviour, the food scouts (about 20%) and nest scouts (less than 5% of new swarm), showing that a similar tendency is expressed across different contexts.

These bees were found to have a brain gene expression that made them genetically predisposed to scouting and “novelty-seeking” behaviour. The bees that act as scouts for the colony have extensive genetic differences to bees that do not scout, including levels of chemicals which are known to control thrill seeking behaviour in humans and mammals.

The study showed that nest scouts were more likely to become food scouts in the new colony, which is an indication that an individual will be novelty-seeking across different settings. Over nine trials, nest scouts were on average 3.4 times more likely to become food scouts after the establishment of the new colony than non-nest scouts, and even up to 5 times more likely in two of the tests (University of Illinois, 8/03/12 ). This demonstrates consistent novelty-seeking behaviour in individual bees.

Figure1: Feeder Discovery Test Results

Researchers then used “feeder discovery” tests to collect true scouts to determine genetic differences (see Fig 1). A large group of bees was trained onto a feeder source. After 2-3 days, a new, “novel” food source was introduced. Each day this feeder was moved and altered to remain “novel”. The bees had the option each day to keep travelling to the known source or explore and search for new feeders. Bees who sought the new feeder 2 or more times were identified as scouts (University of Illinois, 8/03/12), and made up around 30% of 182 bees (6 trials), which reflects previous field observations.

Increased levels of:
Lower levels of:
glutamate transporter Eaat-2 
dopamine receptor DopR1
glutamate transporter  Vglut

glutamate receptor Glu-RI

GABA transporter Gat-a

Table 1: Chemical levels in Scouts

Microarray analysis was used to determine genetic reasons for this behaviour (See Fig 2). (Want to know about Microarray analysis? Click here: Many of the scouts showed different levels of chemicals in catecholamine, glutamate, γ-aminobutyric acid (GABA) and dopamine expressed in their genes (see Table 1), all chemicals that are known to be involved in thrill-seeking behaviour in humans. The researchers backed these results with subsequent tests.
Figure 2 Levels of chemicals expressed in genes of scouts

Non-scouting bees were dosed with these chemicals to determine the responsible brain chemical. They observed over two years that glutamate (monosodium glutamate, or MSG) increased scouting activity by an average of 73% compared to control, while those dosed with dopamine antagonists decreased scouting by 44% (University of Illinois, 8/03/12).

These results demonstrate that insects with these gene expressions will be more likely to scout for the colony or swarm. They are also very similar to the brain gene expression found in humans who “thrill-seek”, where catecholamine, glutamate and dopamine antagonists play an important genetic role in the inheritance of these tendencies. Studies of animals like this will help us better understand behavioural variances in humans and how and why they occur.

 Elizabeth Haswell, P3, Laura Grice, s4287485

ARKive 2012. Apis mellifera [Online] Wildscreen.  [Accessed 2/04/12]

Genetic Science Learning Center (2012). DNA MICROARRAY VIRTUAL LAB [Online]. University of Utah.   [Accessed 2/04/12].

Liang, Z.S. et al, Molecular Determinants of Scouting Behavior in Honey Bees, Science, Vol. 335 no. 6073 pp. 1225-1228 
University of Illinois (UI) at Urbana-Champaign (2012). Insects have 'personalities' too, research on novelty-seeking honey bees indicates. ScienceDaily­/releases/2012/03/120308143201.htm [Accessed 11/03/12]

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