Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan.
Applied Entomology Laboratory, Department of Bioresource Field Science, Kyoto Institute of Technology, 1 Saga-Ippongi-cho, Ukyo-ku, Kyoto, 616-8354, Japan.
J Chem Ecol. 2020 Jun;46(5-6):483-489. doi: 10.1007/s10886-020-01182-6. Epub 2020 May 22.
Pheromone communication helps maintaining the sophisticated colony organization in social insects. In the termite Reticulitermes speratus, there are two functionally distinct soldier groups: royal guards and entrance guards. Royal guards protect kings and queens in the innermost part of the nest, whereas entrance guards prevent predators from intruding into the nest at the periphery. A recent study revealed that younger and older soldiers work as royal and entrance guards, respectively. This age-dependent distribution is thought to help workers to recognize where in the nest they are located. However, it is not known whether workers can discriminate the age of soldiers. Here, we show that the abundance of soldier pheromone changes with age and that workers discriminate a soldier's age by recognizing the pheromone abundance. Gas chromatography-mass spectrometry analysis revealed that the chemical profiles of extracts in three soldier groups of different ages (newly differentiated, royal guard, and entrance guard soldiers) are markedly different. Entrance guard soldiers have the most soldier pheromone among the three age classes. Furthermore, our bioassays suggested that the worker's movement from chamber to chamber is inhibited only when a soldier with less soldier pheromone is located at the chamber entrance. These results suggest that the soldier pheromone functions as a soldier age indicator and that workers change their behavior depending on the age of the soldier defending the chamber entrance. This study contributes to our understanding of the relationship between aging and pheromone communication in social insects.
信息素通讯有助于维持社会性昆虫复杂的群体组织。在白蚁 Reticulitermes speratus 中，有两种功能上明显不同的兵蚁群体：王室卫兵和入口卫兵。王室卫兵保护巢内最深处的国王和王后，而入口卫兵则防止捕食者侵入巢的外围。最近的一项研究表明，年轻和年老的兵蚁分别担任王室卫兵和入口卫兵的角色。这种年龄依赖性的分布被认为有助于工蚁识别它们所在巢内的位置。然而，目前尚不清楚工蚁是否能够辨别兵蚁的年龄。在这里，我们表明兵蚁信息素的丰度随年龄而变化，工蚁通过识别信息素的丰度来辨别兵蚁的年龄。气相色谱-质谱分析显示，三种不同年龄（新分化、王室卫兵和入口卫兵）的兵蚁群体提取物的化学特征明显不同。入口卫兵兵蚁的信息素含量在这三个年龄组中最高。此外，我们的生物测定表明，只有当位于腔室入口处的兵蚁信息素含量较低时，工蚁才会从腔室转移到腔室。这些结果表明，兵蚁信息素是兵蚁年龄的指示物，工蚁会根据守卫腔室入口的兵蚁的年龄改变它们的行为。这项研究有助于我们理解社会性昆虫衰老与信息素通讯之间的关系。
