IFM Biology, Section of Zoology, Linköping University, SE-581 83 Linköping, Sweden.
Chem Senses. 2012 Sep;37(7):631-8. doi: 10.1093/chemse/bjs044. Epub 2012 Mar 26.
The honeybee is one of several insect model systems for the study of olfaction, yet our knowledge regarding the spectrum of odorants detectable by Apis mellifera is limited. One class of odorants that has never been tested so far are the amino acids, which are important constituents of floral nectar. Using the proboscis extension response paradigm, we assessed whether the odor of amino acids is detectable for honeybees and determined olfactory detection thresholds for those amino acids that were detectable. We found that honeybees are able to detect the odor of 5 of the 20 proteinogenic amino acids when presented at a concentration of 50 or 100 mM. Median olfactory detection thresholds for these 5 amino acids were 12.5 mM with L-tyrosine and L-cysteine, 50 mM with L-tryptophan and L-asparagine, and 100 mM with L-proline. All detection thresholds were much higher than reported concentrations of amino acids in floral nectars. We conclude that in the foraging and feeding context, honeybees are likely to detect amino acids through taste rather than olfaction. Across-species comparisons of the detectability of and sensitivity to amino acids suggest that the number of functional genes coding for olfactory receptors may affect both a species' sensitivity for odorants and the breadth of its spectrum of detectable odorants.
蜜蜂是几种昆虫嗅觉研究模式系统之一，但我们对蜜蜂可检测的气味化合物谱的了解是有限的。到目前为止，还从未测试过一类气味化合物，即氨基酸，它们是花蜜的重要组成部分。我们使用触角延伸反应范式来评估氨基酸的气味是否可被蜜蜂察觉，并确定那些可被察觉的氨基酸的嗅觉检测阈值。结果发现，当浓度为 50 或 100mM 时，蜜蜂能够检测到 20 种蛋白氨基酸中的 5 种的气味。这 5 种氨基酸的嗅觉检测中位数阈值分别为 L-酪氨酸和 L-半胱氨酸 12.5mM，L-色氨酸和 L-天冬酰胺 50mM，L-脯氨酸 100mM。所有检测阈值都远高于花蜜中报道的氨基酸浓度。因此，我们得出结论，在觅食和进食的情况下，蜜蜂可能通过味觉而不是嗅觉来检测氨基酸。对氨基酸的可检测性和敏感性的跨物种比较表明，编码嗅觉受体的功能基因数量可能会影响物种对气味的敏感性以及其可检测气味化合物的范围。
