Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwakecho, Kyoto 606-8502, Japan.
Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwakecho, Kyoto 606-8502, Japan
Biol Lett. 2018 Mar;14(3). doi: 10.1098/rsbl.2018.0025.
Who should take on risky tasks in an age-heterogeneous society? Life-history theory predicts that, in social insects, riskier tasks should be undertaken by sterile individuals with a shorter life expectancy. The loss of individuals with shorter life expectancy is less costly for colony reproductive success than the loss of individuals with longer life expectancy. Termite colonies have a sterile soldier caste, specialized defenders engaged in the most risky tasks. Here we show that termite soldiers exhibit age-dependent polyethism, as old soldiers are engaged in front-line defence more than young soldiers. Our nest defence experiment showed that old soldiers went to the front line and blocked the nest opening against approaching predatory ants more often than young soldiers. We also found that young soldiers were more biased toward choosing central nest defence as royal guards than old soldiers. These results demonstrate that termite soldiers have age-based task allocation, by which ageing predisposes soldiers to switch to more dangerous tasks. This age-dependent soldier task allocation increases the life expectancy of soldiers, allowing them to promote their lifetime contribution to colony reproductive success.
在一个年龄异质的社会中，谁应该承担风险任务？ 生活史理论预测，在社会性昆虫中，风险更大的任务应由预期寿命较短的无菌个体承担。与预期寿命较长的个体相比，短寿命个体的损失对群体繁殖成功率的影响较小。白蚁群体具有无菌的兵蚁阶层，专门从事最危险的任务。在这里，我们表明白蚁兵蚁表现出年龄依赖性的多态现象，年老的兵蚁比年轻的兵蚁更经常参与前线防御。我们的巢防御实验表明，年老的兵蚁更经常前往前线并阻止巢穴开口，以抵御接近的捕食性蚂蚁，而年轻的兵蚁则较少这样做。我们还发现，年轻的兵蚁比年老的兵蚁更倾向于选择作为皇家卫兵的中央巢防御。这些结果表明，白蚁兵蚁具有基于年龄的任务分配，即随着年龄的增长，兵蚁更容易转向更危险的任务。这种基于年龄的兵蚁任务分配增加了兵蚁的预期寿命，使它们能够促进其对群体繁殖成功率的终生贡献。
