Nestmate Recognition In Honey Bees Research Articles

Natural biocide disrupts nestmate recognition in honeybees

Honeybee colonies are under the threat of many stressors, biotic and abiotic factors that strongly affect their survival. Recently, great attention has been directed at chemical pesticides, including their effects at sub-lethal doses on bee behaviour and colony success; whereas the potential side effects of natural biocides largely used in agriculture, such as entomopathogenic fungi, have received only marginal attention. Here, we report the impact of the fungus Beauveria bassiana on honeybee nestmate recognition ability, a crucial feature at the basis of colony integrity. We performed both behavioural assays by recording bee guards’ response towards foragers (nestmate or non-nestmate) either exposed to B. bassiana or unexposed presented at the hive entrance, and GC-MS analyses of the cuticular hydrocarbons (CHCs) of fungus-exposed versus unexposed bees. Our results demonstrated that exposed bees have altered cuticular hydrocarbons and are more easily accepted into foreign colonies than controls. Since CHCs are the main recognition cues in social insects, changes in their composition appear to affect nestmate recognition ability at the colony level. The acceptance of chemically unrecognizable fungus-exposed foragers could therefore favour forager drift and disease spread across colonies.

Muscarinic acetylcholine receptors are required for nestmate-odor memory retrieval but not for olfaction in harvester ants (Pogonomyrmex barbatus)

The ability of social insects such as ants to distinguish between nestmates and non-nestmates is odor-based, learned and critical to the survival of the colony. However, little is known about how the brain processes the olfactory cues associated with nestmate recognition. Previous studies have shown that inhibition of muscarinic acetylcholine receptors with a competitive inhibitor, scopolamine affects nestmate recognition in honeybees, causing them to mistakenly attack nestmates. This suggests that muscarinic receptors may be required for either olfaction and/or retrieval of odor memory. The aim of this study was to further investigate the role of muscarinic receptors in nestmate recognition in another social insect, the harvester ant (Pogonomyrmex barbatus). Focal ants were fed either scopolamine dissolved in sucrose or sucrose alone (control) for approximately 72 hours, then placed in an arena with either a nestmate or a genetically unrelated non-nestmate. We videotaped their interactions and determined the frequency with which focal ants exhibited aggressive behaviors toward the introduced ants. Focal ants treated with scopolamine exhibited inappropriate aggressive behaviors toward nestmates with a significantly higher frequency than did the controls, but with the same frequency that they exhibited aggressive behaviors toward non-nestmates. These results suggest that scopolamine-treated ants can't distinguish nestmates from non-nestmates. However, scopolamine-treated focal ants did respond appropriately to the presence of an olfactory repellent, indicating that scopolamine does not disrupt olfaction. The data support a role for muscarinic receptors in odor memory retrieval rather than in odor perception, and indicate that this role is conserved in P. barbatus.

Use of Flax Oil to Influence Honey Bee Nestmate Recognition

Fatty acids, normally found in comb wax, have a strong influence on nestmate recognition in honey bees, Apis mellifera L. Previous work has shown that bees from different colonies, when treated with 16- or 18-carbon fatty acids, such as oleic, linoleic, or linolenic acids, are much less likely to fight than bees from two colonies when only one of the two is treated. Previous work also shows that the influence of comb wax on recognition has practical applications; transfer of empty comb between colonies, before merger of those colonies, reduces fighting among workers within the merged colony. Flax oil contains many of the same fatty acids as beeswax. Here, we tested the hypothesis that treatment of individual bees with flax oil affects nestmate recognition; the results proved to be consistent with this hypothesis and showed that treated bees from different colonies were less likely to fight than untreated bees. These results suggest that flax oil may be useful in facilitating colony mergers.

Honeybee nestmate recognition: the thermal behaviour of guards and their examinees.

In honeybee colonies, guards protect their nest from various robbers including bees from other colonies. Infrared thermography showed that the guards and the bees examined by them (examinees) differ considerably in their thermal behaviour according to their particular role in the nestmate recognition process. The thorax surface temperature was on average higher and more variable in the examinees (36.1 degrees C, S.D.=4.14, N=1545, 303 bees) than in the guards (34.0 degrees C, S.D.=2.00, N=1681, 772 bees). During thorough examinations lasting longer than 30 s, more than 60 % of the examinees showed phases of intense thoracic heating of more than 2 degrees C (maximum temperature 48.5 degrees C), whereas most guards cooled down. Our data suggest that these examinees heat up their surface to enhance chemical signalling during examinations.

Floral oils: their effect on nestmate recognition in the honey bee, Apis mellifera

Floral oils are an important component of the honey bee's olfactory environment. We use laboratory and field tests to determine whether floral oils affect nestmate recognition in honey bees. In the laboratory, newly emerged worker bees, that have not been exposed to comb wax, responded more aggressively to bees that had been exposed to floral oils than unexposed control bees. In the field, guard bees did not respond differently to foragers that had been exposed to floral oils. Floral oils may play a supplementary role in nestmate recognition; however, if they have any effect it is secondary to cues acquired from comb way during development.

The role of wax comb in honey bee nestmate recognition

WORKER honey bees,Apis mellifera, are able to discriminate between combs on the basis of genetic similarity to a learned comb. The nestmate recognition cues that they acquire from the comb also have a genetically correlated component. Cues are acquired from comb in very short exposure periods (5min or less) and can be transferred among bees that are in physical contact. Gas chromatographic analysis demonstrates that bees with exposure to comb have different chemical surface profiles than bees without such exposure. These results support the hypothesis that comb-derived recognition cues are highly important in honey bee nestmate recognition. These cues are at least in part derived from the wax itself, rather than from floral scents that have been absorbed by the wax.

Honeybee nestmate recognition: Effects of queen fecal pheromones

Previous work has shown that queen honeybees,Apis mellifera, produce waxy esters composed of 8-14 carbon acids and 6-14 carbon alcohols in their feces. We tested these esters for effects on nestmate recognition; 11 of the 12 esters tested significantly modified the recognition characteristics of worker honeybees. Pairwise tests showed that workers can discriminate between at least some pairs of queen esters and that workers can discriminate between a queen ester and hexadecane (another known nestmate recognition cue). These results suggest that a queen may use the esters to enable workers to recognize her or to scent-mark her colony.

Honey bee, , nestmate discrimination: hydrocarbon effects and the evolutionary implications of comb choice

Comb wax in honey bee colonies serves as a source and medium for transmission of recognition cues. Worker honey bees learn the identity of their primary nesting material, the wax comb, within an hour of emergence. In an olfactometer, bees discriminate between combs on the basis of odour; they prefer the odours of previously learned combs. Representatives of three of the most common compound classes in bee's wax were surveyed for effects on nestmate discrimination behaviour. Hexadecane, octadecane, tetracosanoic acid and methyl docosanoate make worker honey bees less acceptable to their untreated sisters. Other similar compounds did not have this effect. These findings support the hypothesis that nestmate recognition in honey bees is mediated by many different compounds, including some related to those found in comb wax.

Honey bee, Apis mellifera, nestmate discrimination: hydrocarbon effects and the evolutionary implications of comb choice

Comb wax in honey bee colonies serves as a source and medium for transmission of recognition cues. Worker honey bees learn the identity of their primary nesting material, the wax comb, within an hour of emergence. In an olfactometer, bees discriminate between combs on the basis of odour; they prefer the odours of previously learned combs. Representatives of three of the most common compound classes in bee's wax were surveyed for effects on nestmate discrimination behaviour. Hexadecane, octadecane, tetracosanoic acid and methyl docosanoate make worker honey bees less acceptable to their untreated sisters. Other similar compounds did not have this effect. These findings support the hypothesis that nestmate recognition in honey bees is mediated by many different compounds, including some related to those found in comb wax.

Nestmate recognition in honey bees

The recognition cues by which nestmate worker honeybees are discriminated from nonnestmates were investigated using new experimental techniques. The experiments described in this paper support the contention that the recognition cue is acquired prior to emergence as an adult. The cue probably has a genetic, rather than an environmental, source. Previous findings, which indicated that worker honeybees are recognized on the basis of environmentally acquired odours, do not contradict this result. Rather, bees probably use whatever cues are available for recognition. When environmental odour sources are carefully controlled, cues remain that allow discrimination of nestmate versus nonnestmate individuals.