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Genetics of Hygienic Behaviour of Honeybees, Apis mellifera
Hygienic behaviour is the term used to describe nest cleaning carried out by worker bees to remove dead larvae or pupae from brood cells. There are two distinct subtasks – uncapping of a brood cell and the removal of the larva or pupa from the cell. Recent work on the genetic basis of hygienic behaviour showed that several qualitative trait loci are involved in the expression of this behaviour. The first part of my study was to test putative genetic markers as possible candidates for marker-assisted breeding. Two of the markers tested were present in significantly different frequencies in samples from hygienic and non-hygienic colonies. Thus these markers have excellent potential for use as a diagnostic tool for identifying hygienic stock. Sequencing of neighbouring DNA regions may provide more insight into the genetic elements responsible for the phenotypic differences between hygienic and non-hygienic colonies.
Hygienic behaviour is a trait which is selected at the colony level. The second part of my study was to examine the effect of colony genotypic composition on behaviour at the individual level. Bees from two different colonies selected for hygienic behaviour and lack of hygienic behaviour were used to create colonies consisting of bees from both hygienic and non-hygienic lines in different proportions. The aspects I looked at were:
1) Are hygienic bees more likely to be found on areas of the comb with dead
brood?
2) Are hygienic bees more likely to perform hygienic behaviour than non-hygienic
bees?
3) Does the age at which hygienic bees perform hygienic behaviour differ from
that of non-hygienic bees?
I found that the proportion of hygienic bees found on areas of dead brood was higher than elsewhere in the colony. The hygienic bees were more likely to be performing hygienic behaviour than non-hygienic bees. Thus hygienic bees may actively seek the odour given off by dead brood to carry out nest cleaning. An alternative hypothesis is that having found the dead brood by chance, hygienic bees remain in the area longer as they are more likely to start the hygienic tasks. Hygienic bees carrying out hygienic behaviour were also younger than non-hygienic bees.
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